Search

Background and Aims: Coronavirus disease 2019 (COVID‐19) has become a global pandemic and led to increased mortality and morbidity. Vaccines against the etiologic agent; severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) were approved for emergency use on different platforms. In the early phase of the pandemic, Thai healthcare workers (HCWs) received CoronaVac, an inactivated vaccine, as the first vaccine against SARS‐CoV‐2, followed by ChAdOx1 nCoV‐19, a viral vector‐based vaccine, or BNT162b2, an mRNA vaccine, as a booster dose. This preliminary study evaluated the immunogenicity of ChAdOx1 nCoV‐19 and BNT162b2 as a booster dose in HCWs who previously received two doses of CoronaVac. Methods: Ten HCW participants received ChAdOx1 nCoV‐19 and another 10 HCWs received BNT162b2 as a booster dose after two doses of CoronaVac. Anti‐RBD IgG, neutralizing antibodies (NAb), and cellular immunity, including interferon‐gamma (IFN‐γ)‐releasing CD4, CD8, double negative T cells, and NK cells, were measured at 3 and 5 months after the booster dose. Results: There was no significant difference in anti‐RBD IgG levels at 3 and 5 months between the two different types of booster vaccine. The levels of anti‐RBD IgG and NAb were significantly decreased at 5 months. HCWs receiving BNT162b2 had significantly higher NAb levels than those receiving ChAdOx1 nCoV‐19 at 5 months after the booster dose. IFN‐γ release from CD4 T cells was detected at 3 months with no significant difference between the two types of booster vaccines. However, IFN‐γ‐releasing CD4 T cells were present at 5 months in the ChAdOx1 nCoV‐19 group only. Conclusion: ChAdOx1 nCoV‐19 or BNT162b2 can be used as a booster dose after completion of the primary series primed by inactivated vaccine. Although the levels of immunity decline at 5 months, they may be adequate during the first 3 months after the booster dose. [ABSTRACT FROM AUTHOR]

Questions remain regarding the effect of baseline host and exposure factors on vaccine efficacy (VE) across pathogens and vaccine platforms. We report placebo-controlled data from four Phase 3 COVID-19 trials during the early period of the pandemic. This was a cross-protocol analysis of four randomized, placebo-controlled efficacy trials (Moderna/mRNA1273, AstraZeneca/AZD1222, Janssen/Ad26.COV2.S, and Novavax/NVX-CoV2373) using a harmonized design. Trials were conducted in the United States and international sites in adults ≥ 18 years of age. VE was assessed for symptomatic and severe COVID-19. We analyzed 114,480 participants from both placebo and vaccine arms, enrolled July 2020 to February 2021, with follow up through July 2021. VE against symptomatic COVID-19 showed little heterogeneity across baseline socio-demographic, clinical or exposure characteristics, in either univariate or multivariate analysis, regardless of vaccine platform. Similarly, VE against severe COVID-19 in the single trial (Janssen) with sufficient endpoints for analysis showed little evidence of heterogeneity. COVID-19 VE is not influenced by baseline host or exposure characteristics across efficacy trials of different vaccine platforms and countries when well matched to circulating virus strains. This supports use of these vaccines, regardless of platform type, as effective tools in the near term for reducing symptomatic and severe COVID-19, particularly for older individuals and those with common co-morbidities during major variant shifts. Clinical trial registration numbers: NCT04470427, NCT04516746, NCT04505722, and NCT04611802.

Abstract Background and Aims Coronavirus disease 2019 (COVID‐19) has become a global pandemic and led to increased mortality and morbidity. Vaccines against the etiologic agent; severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) were approved for emergency use on different platforms. In the early phase of the pandemic, Thai healthcare workers (HCWs) received CoronaVac, an inactivated vaccine, as the first vaccine against SARS‐CoV‐2, followed by ChAdOx1 nCoV‐19, a viral vector‐based vaccine, or BNT162b2, an mRNA vaccine, as a booster dose. This preliminary study evaluated the immunogenicity of ChAdOx1 nCoV‐19 and BNT162b2 as a booster dose in HCWs who previously received two doses of CoronaVac. Methods Ten HCW participants received ChAdOx1 nCoV‐19 and another 10 HCWs received BNT162b2 as a booster dose after two doses of CoronaVac. Anti‐RBD IgG, neutralizing antibodies (NAb), and cellular immunity, including interferon‐gamma (IFN‐γ)‐releasing CD4, CD8, double negative T cells, and NK cells, were measured at 3 and 5 months after the booster dose. Results There was no significant difference in anti‐RBD IgG levels at 3 and 5 months between the two different types of booster vaccine. The levels of anti‐RBD IgG and NAb were significantly decreased at 5 months. HCWs receiving BNT162b2 had significantly higher NAb levels than those receiving ChAdOx1 nCoV‐19 at 5 months after the booster dose. IFN‐γ release from CD4 T cells was detected at 3 months with no significant difference between the two types of booster vaccines. However, IFN‐γ‐releasing CD4 T cells were present at 5 months in the ChAdOx1 nCoV‐19 group only. Conclusion ChAdOx1 nCoV‐19 or BNT162b2 can be used as a booster dose after completion of the primary series primed by inactivated vaccine. Although the levels of immunity decline at 5 months, they may be adequate during the first 3 months after the booster dose.

Measuring immune correlates of disease acquisition and protection in the context of a clinical trial is a prerequisite for improved vaccine design. We analysed binding and neutralizing antibody measurements 4 weeks post vaccination as correlates of risk of moderate to severe-critical COVID-19 through 83 d post vaccination in the phase 3, double-blind placebo-controlled phase of ENSEMBLE, an international randomized efficacy trial of a single dose of Ad26.COV2.S. We also evaluated correlates of protection in the trial cohort. Of the three antibody immune markers we measured, we found most support for 50% inhibitory dilution (ID50) neutralizing antibody titre as a correlate of risk and of protection. The outcome hazard ratio was 0.49 (95% confidence interval 0.29, 0.81; P = 0.006) per 10-fold increase in ID50; vaccine efficacy was 60% (43%, 72%) at non-quantifiable ID50 (

Background: Hemophagocytic lymphohistiocytosis (HLH) is a rare systemic inflammatory disease commonly characterized by histiocyte infiltration in multiple organs, such as the liver, spleen, lymph nodes, bone marrow, and central nervous system. The clinical features of HLH include fever, splenomegaly, cytopenia, hypertriglyceridemia, hypofibrinogenemia, and elevated blood ferritin levels. HLH is categorized as either primary or secondary. Coronavirus disease 2019 (COVID-19) vaccines may occasionally trigger secondary HLH, which is related to hyperinflammatory syndrome. Case presentation: A 58-year-old woman, previously diagnosed with Graves’ disease, presented with cognitive decline 2 weeks after receiving the first dose of the ChAdOx1 nCoV-19 vaccine. Brain MRI revealed a hyperintense lesion on T2-weighted and fluid-attenuated inversion recovery images in the bilateral subcortical white matter and right periventricular area. Vaccination-associated acute disseminated encephalomyelitis was suspected and methylprednisolone and intravenous immunoglobulin (IVIg) were administered. From the 5th day of IVIg administration, the patient developed fever and pancytopenia. In the findings of bone marrow biopsy, hemophagocytosis was not observed; however, six of the eight diagnostic criteria for HLH-2004 were met, raising the possibility of HLH. Although there was no definitive method to confirm causality, considering the temporal sequence, suspicion arose regarding vaccine-induced HLH. Splenectomy was considered for therapeutic and diagnostic purposes; however, the patient died on the 28th day of hospitalization owing to multiple organ failure. Conclusion: To date, 23 cases of COVID-19 vaccine-related HLH have been reported. Additionally, HLH in COVID-19 patients has been reported in various case reports. To the best of our knowledge, this is the first reported case of central nervous system involvement in HLH related to any type of COVID-19 vaccine. This case suggests that even when there are no systemic symptoms after COVID-19 vaccination, HLH should be considered as a differential diagnosis if brain lesions are suggestive of CNS demyelinating disease. [ABSTRACT FROM AUTHOR]

Neutrophil extracellular traps (NETs) play a role in innate pathogen defense and also trigger B‐cell response by providing antigens. NETs have been linked to vaccine‐induced thrombotic thrombocytopenia. We postulated a potential link between NET biomarkers, NET‐promoting autoantibodies, and adverse events (AEs) after COVID‐19 vaccine boosters. Healthy donors (HDs) who received ChAdOx1‐S (A), mRNA‐1273 (M), or recombinant protein (MVC–COV1901) vaccines at the National Taiwan University Hospital between 2021 and 2022 were recruited. We measured serial NET‐associated biomarkers, citrullinated‐histone3 (citH3), and myeloperoxidase (MPO)‐DNA. Serum citH3 and MPO‐DNA were significantly or numerically higher in HDs who reported AEs (n = 100, booster Day 0/Day 30, p = 0.01/p = 0.03 and p = 0.30/p = 0.35, respectively). We also observed a positive correlation between rash occurrence in online diaries and elevated citH3. A linear mixed model also revealed significantly higher citH3 levels in mRNA‐1273/ChAdOx1‐S recipients than MVC‐COV1901 recipients. Significant positive correlations were observed between the ratios of anti‐heparin platelet factor 4 and citH3 levels on Booster Day 0 and naïve and between the ratios of anti‐NET IgM and citH3 on Booster Day 30/Day 0 in the AA‐M and MM‐M group, respectively. The increased levels of citH3/MPO‐DNA accompanied by NET‐promoting autoantibodies suggest a potential connection between mRNA‐1273/ChAdOx1‐S vaccines and cardiovascular complications. These findings provide insights for risk assessments of future vaccines. [ABSTRACT FROM AUTHOR]

A booster dose of a COVID-19 vaccine has been proven effective in restoring vaccine effectiveness and is currently recommended for use in some populations at risk of severe COVID-19 infection. Since sex differences in adverse events are significant in response to the vaccines, the safety of booster selection must be studied to avoid serious adverse events (SAE), such as life-threatening diseases. First, this study aimed to identify sex differences in SAE incidences using a prospective cohort design. Second, a nested unmatched case-control study was used to identify factors associated with reported SAE within 30 days after the booster shot. Multivariable logistic regression indicated the adjusted odds ratio by accounting for host and vaccine variables, thus, policy effects. The findings confirmed that SAE was rare and that age-sex-dominated disease classifications differed. Specific to SAE following the booster dose, we found that females aged 12–40 had a higher risk of being reported with SAE than males of the same age, while males over 50 had a higher risk than females. Other risk factors identified were the presence of metabolic syndrome and the use of certain vaccine brands. Mechanisms could be explained by individual host responses rather than the vaccines' direct effect. Therefore, SAE could be preventable by age-sex-specific vaccine selection, post-vaccination precautions, and early symptom detection. Future vaccine development should aim to limit host-specific reactogenicity for safety concerns. [ABSTRACT FROM AUTHOR]

New variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have emerged, imposing the need for periodic booster doses. However, whether booster doses should be applied to the entire population or groups, and the booster doses interval, remains unclear. In this study, we evaluated humoral reactivity kinetics from before the first dose to 180 days after the third booster dose in different schedules in a well-controlled health worker cohort. Among the 2,506 employees, the first 500 vaccinated health workers were invited to participate. The third booster dose was administered 8 months after the first dose. Among the invited participants, 470 were included in the study; 258 received inactivated vaccine CoronaVac (VAC group) and 212 received viral vector vaccine ChAdOx1 (AZV group). The groups were homogeneous in terms of age and sex. 347 participants were followed up after the booster dose with AZV or BNT162b2 (Pfizer, BNT group): 63 with VAC/AZV, 117 with VAC/BNT, 72 with the AZV/AZV and 95 with AZV/BNT schedules. Blood samples were collected immediately before, 28 days after each dose and 180 days after the primary vaccination and booster dose. Anti-SARS-CoV-2 antibodies were measured by chemiluminescence and plaque reduction neutralization test (PRNT). Plasma immune mediators were quantified using a multiplex immunoassay. Geometric mean of antibodies increased 28 days after the second dose with 100 % seroconversion rate in both groups and decreased 180 days after the first dose. In the baseline-seropositive VAC group, the levels of plasma immune mediators increased after the second dose. Booster dose was applied at 4–6 months after the primary vaccination. Heterologous booster in VAC or AZV primary vaccinees were effective maintaining the titers of anti-SARS-CoV-2 antibodies even after 6 months of follow-up. The heterologous schedule induced higher and stable antibody reactivity, even after 180 days, protecting to ancestral (Wuhan), Delta, and Omicron variants. [ABSTRACT FROM AUTHOR]

An effective worldwide vaccination campaign started and is still being carried out in the face of the coronavirus disease 2019 (COVID-19) pandemic. While vaccines are great tools to confront the pandemic, predominantly adenoviral vector-based vaccines can cause a rare severe adverse effect, termed vaccine-induced immune thrombocytopenia and thrombosis (VITT), in about 1 in 100,000 vaccinated individuals. VITT is diagnosed 5–30 days post-vaccination and clinically characterized by thrombocytopenia, strongly elevated D-dimer levels, platelet-activating anti-platelet factor 4 (PF4) antibodies and thrombosis, especially at atypical sites such as the cerebral venous sinus and/or splanchnic veins. There are striking similarities between heparin-induced thrombocytopenia (HIT) and VITT. Both are caused by anti-PF4 antibodies, causing platelet and leukocyte activation which results in massive thrombo-inflammation. However, it is still to be determined why PF4 becomes immunogenic in VITT and which constituent of the vaccine triggers the immune response. As VITT-like syndromes are increasingly reported in patients shortly after viral infections, direct virus-PF4 interactions might be most relevant. Here we summarize the current information and hypotheses on the pathogenesis of VITT and address in vivo models, especially murine models for further studies on VITT. [ABSTRACT FROM AUTHOR]

COVID-19, caused by the SARS-CoV-2 virus, is a global respiratory syndrome with high mortality rates. Vaccination is currently the only proven method to prevent the disease, although the role of lab data in assessing efficacy remains uncertain. This study aimed to assess spike-binding and neutralizing antibody levels following full vaccination with Oxford/AstraZeneca (ChAdOx1 nCoV-19) or CoronaVac in healthcare workers in southeastern Brazil. ChAdOx1 nCoV-19 and CoronaVac induced IgG antibodies against trimeric spike glycoproteins in 99.5% and 80.9% of individuals, respectively. Neutralizing antibodies were produced against two viral strains groups: variants group 1 (Wuhan-Hu-1, Alpha) and variants group 2 (Beta, Gamma) with neutralization rates of 88.3% and 78.2% for ChAdOx1 nCoV-19, and 68.1% and 48.9% for CoronaVac. No associations were found between neutralizing levels and comorbidities, age, or side effects. A positive correlation was observed between IgG antibody concentrations against trimeric spike glycoproteins and neutralizing levels for both vaccines and variants. These findings indicate that both vaccines induced reasonable levels of neutralizing antibodies against variants group 1, but only ChAdOx1 nCoV-19 maintained acceptable levels against a variant strain. The study suggests that evaluating vaccine responses to different pathogen strains can aid in managing healthcare workforce concerns and improve vaccine selection, thereby enhancing overall vaccination strategies.

Background: While care for COVID-19 patients has improved with clinical experience, there remains a critical and unmet medical need for vaccines suitable to help or alleviate COVID-19 infections during the pandemic. Although the available vaccines have some benign autoimmune side effects, such as mild thrombocytopenia, in rare cases, the side effects, such as central vein thrombosis, severe thrombocytopenia, and intracranial hemorrhage, are life-threatening. Case Presentation: We report 3 female patients (19, 24, and 43 years old) who developed cerebral venous sinus thrombosis (CVST) after the AstraZeneca ChAdOx1-S COVID-19 vaccination. Despite medical and surgical treatment, they finally became brain dead. Conclusion: Medical professionals should know the manifestations and diagnostic methods of CVST after the COVID-19 vaccination and how to properly treat and manage it.

BackgroundThe safety and efficacy of the AZD1222 (ChAdOx1 nCoV-19) vaccine in a large, diverse population at increased risk for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in the United States, Chile, and Peru has not been known.MethodsIn this ongoing, double-blind, randomized, placebo-controlled, phase 3 clinical trial, we investigated the safety, vaccine efficacy, and immunogenicity of two doses of AZD1222 as compared with placebo in preventing the onset of symptomatic and severe coronavirus disease 2019 (Covid-19) 15 days or more after the second dose in adults, including older adults, in the United States, Chile, and Peru.ResultsA total of 32,451 participants underwent randomization, in a 2:1 ratio, to receive AZD1222 (21,635 participants) or placebo (10,816 participants). AZD1222 was safe, with low incidences of serious and medically attended adverse events and adverse events of special interest; the incidences were similar to those observed in the placebo group. Solicited local and systemic reactions were generally mild or moderate in both groups. Overall estimated vaccine efficacy was 74.0% (95% confidence interval [CI], 65.3 to 80.5; P

Vaccines are crucial for controlling the COVID-19 pandemic, and booster doses are becoming increasingly important. This study aimed to assess the efficacy of the ChAdOx1 nCoV-19 vaccine from AstraZeneca as a third dose in healthcare workers at different time intervals (one, three, and six months). Two methods to measure immune response—ELISA (EUROIMMUN Medizinische Labordiagnostika AG, Luebeck, Germany) and ELISpot (Mabtech AB, Macka Strand, Sweden)—were used. A total of 170 participants were included in the study. The results showed that while IgG levels decreased at six months compared to levels at one and three months, they were still significantly higher than the baseline. Furthermore, neutralizing levels at three and six months and after the third dose were not significantly different. These findings suggest that the immune response induced by the vaccine was robust and effective for several months. These results have significant implications for public health policymakers, as they provide strong support for booster vaccinations. The ChAdOx1 nCoV-19 vaccine appears to be a reliable option for preventing the spread of COVID-19, and this study provides valuable information for healthcare workers and policymakers in managing the pandemic.

Key Clinical Message: Immune thrombocytopenic purpura (ITP) is an autoimmune disease characterized by a low platelets count. In this paper, we present a case of ITP relapse in a 31‐year‐old Iranian woman as a potential complication of the AstraZeneca vaccine. [ABSTRACT FROM AUTHOR]

This real-world study was conducted to assess the adverse effects following immunization (AEFI) and immunogenicity of ChAdO×1 nCoV-19 vaccine in terms of neutralising antibody titers and to study the effects of covariates such as age, sex, comorbidities and prior COVID status on these outcomes. Also, the effectiveness of the vaccine based on interval between the two doses was also investigated. A total of 512 participants (M/F=274/238) aged 35(18–87) years comprising a mixed population of healthcare workers, other frontline workers and general public were enrolled between March and May 2021. Records for adverse events if any were collected telephonically by following up with participants up to 6 months post first dose and graded as per Common Terminology Criteria for Adverse Events (CTCAE) version 5. Blood samples for measuring antibody titers against the receptor binding domain (RBD) were collected serially using a convenient sampling strategy up to 6 months after the first dose. Data on breakthrough COVID infection was collected telephonically till December 2021. Incidence of local reactions was higher after first dose at 33.4 % (171/512) compared to those after second dose at 12.9 % (66/512). Commonest side effect observed was injection site pain after the first (87.1 %; 149/171) and second (87.9 %; 56/66) dose respectively. Among systemic reactions, fever was the most common manifestation followed by myalgia and headache. Female sex (p<0⸱001) and age less than 60 years (p<0⸱001) had significantly higher predilection for systemic toxicities. Age ≤60 years (p=0.024) and prior-COVID (p<0.001) were found to be significantly associated with higher antibody titers, however, no association was found between these variables and breakthrough COVID infection. Longer spacing between the doses (≥6 weeks) was found to offer better protection against breakthrough infection compared to a spacing of 4 weeks. All breakthroughs were mild-moderate in severity, not requiring hospitalization. The ChAdOx1 nCov-19 vaccine is apparently safe and effective against SARS-CoV-2 virus infection. Prior COVID infection and younger age group achieve higher antibody titers, but no additional protection. Delaying the second dose up to at least 6 weeks is more effective compared to shorter spacing between doses. [ABSTRACT FROM AUTHOR]

Background: While care for coronavirus disease 2019 (COVID-19) patients has improved with clinical experience, there remains a critical and unmet medical need for vaccines suitable to help or alleviate COVID-19 infections during the pandemic. Although the available vaccines have some benign autoimmune side effects, such as mild thrombocytopenia, in rare cases, the side effects, such as central vein thrombosis, severe thrombocytopenia, and intracranial hemorrhage, are life-threatening. Case Presentation: We report 3 female patients (19, 24, and 43 years old) who developed cerebral venous sinus thrombosis (CVST) after the AstraZeneca ChAdOx1-S COVID-19 vaccination. Despite medical and surgical treatment, they finally became brain dead. Conclusion: Medical professionals should know the manifestations and diagnostic methods of CVST after the COVID-19 vaccination and how to properly treat and manage it. [ABSTRACT FROM AUTHOR]

The SARS-CoV-19 pandemic overwhelmed multiple healthcare systems across the world. Patients with underlying medical conditions such as obesity or diabetes were particularly vulnerable, had more severe symptoms, and were more frequently hospitalized. To date, there have been many studies on the severity of SARS-CoV-2 in patients with metabolic disorders, but data on the efficiency of vaccines against COVID-19 are still limited. This paper aims to provide a comprehensive overview of the effectiveness of COVID-19 vaccines in individuals with diabetes, insulin resistance, and obesity. A comparison is made between the immune response after vaccination in patients with and without metabolic comorbidities. Additionally, an attempt is made to highlight the mechanisms of immune stimulation affected by SARS-CoV-2 vaccines and how metabolic comorbidities modulate these mechanisms. The focus is on the most common COVID-19 vaccines, which include mRNA vaccines such as Pfizer-BioNTech and Moderna, as well as viral vector vaccines such as AstraZeneca and Johnson & Johnson. Furthermore, an effort is made to clarify how the functional differences between these vaccines may impact the response in individuals with metabolic disorders, drawing from available experimental data. This review summarizes the current knowledge regarding the post-vaccination response to COVID-19 in the context of metabolic comorbidities such as diabetes, insulin resistance, and obesity. [ABSTRACT FROM AUTHOR]

The rapid availability of effective vaccines against SARS-CoV-2 was key during the COVID-19 pandemic. However, vaccine hesitancy and relatively low vaccine coverage rates among the general population and particularly vulnerable populations such as healthcare staff reduced the potential benefits of these vaccines. During the early phase of the pandemic, fear of vaccine-related adverse events was common among individuals who refused vaccination. Between March and May 2021, we comparatively assessed the self-reported reactogenicity of different SARS-CoV-2 prime-boost regimens using mRNA-based (BNT162b2 and mRNA-1273) and vector-based vaccines (ChAdOx1 nCoV-19) in (a) healthcare workers (HCW), and (b) police staff from southwest Germany. The majority of participants (71.8%; 1564/2176) received a homologous vaccination. Among HCW, 75.0% were female, whereas 70.0% of police staff were male. The most frequently reported reactions following the first vaccine administration were pain at the injection site (77.94%; 1696/2176), tiredness (51.75%; 1126/2176), and headache (40.44%; 880/2176), which were more commonly reported by HCW as compared to police staff. In homologous, mRNA-based and heterologous vaccination schedules, more reactions were reported after the second vaccine dose. We conclude that the frequency and intensity of self-perceived vaccine reactogenicity may differ between specific population groups and might be mitigated by tailored communication strategies. [ABSTRACT FROM AUTHOR]

ChAdOx1 nCoV-19 (AZD1222) is a replication-deficient chimpanzee adenovirus vectored vaccine developed by Oxford and AstraZeneca for a disease we all know as Coronavirus, or COVID-19. Ongoing clinical studies reveal that the ChAdOx1 nCoV-19 vaccine has a tolerable safety profile and is effective against symptomatic COVID-19. This vaccine may prove crucial in boosting herd immunity, averting life threatening illness, and relieving the current pandemic. In this mini review, we performed a thorough literature search through PubMed and Google Scholar and reported various case reports associated with complications of the adenovirus-vectored COVID-19 vaccine. Various adverse effects of the ChAdOx1 nCoV-19 vaccine were reported around the globe, which were often serious but rare and developed into life-threatening pathologies such as GBS, thrombocytopenia, demyelinating neuropathies, progressive dementia, cerebral infarction, IgA vasculitis, hemophagocytic lymphohistiocytosis, herpes zoster, cutaneous reactions, and vein thrombosis. These worldwide reported complications, which are usually rare and severe, will aid clinicians in understanding and managing unforeseen situations. There is a need for more research to find out more about these complications and their etiopathogenesis. However, the benefits of these vaccinations for stopping the spread of the outbreak and lowering the fatality rate outweigh the potential risk of the uncommon complications.

Abstract Background Both BNT162b2 (Pfizer–BioNTech) and ChAdOx1 nCoV-19 (Oxford–AstraZeneca) vaccines have shown high efficacy against COVID-19 in randomized controlled trials. However, their comparative effectiveness against COVID-19 is unclear in the real world. We evaluated the comparative effectiveness of the BNT162b2 and ChAdOx1 nCoV-19 vaccines against COVID-19 in the UK general population. Methods We emulated a target trial using IQVIA Medical Research Database (IMRD), an electronic primary care database from the UK (2021). We included 1,311,075 participants, consisting of 637,549 men and 673,526 women age≥18 years, who received vaccination with BNT162b2 or ChAdOx1 nCoV-19 between January 1 and August 31, 2021. The outcomes consisted of confirmed diagnosis of SARS-CoV-2 infection, hospitalisation for COVID-19 and death from COVID-19 in the IMRD. We performed a cox-proportional hazard model to compare the risk of each outcome variable between the two vaccines adjusting for potential confounders with time-stratified overlap weighting of propensity score (PS). Results During a mean of 6.7 months of follow-up, 20,070 confirmed SARS-CoV-2 infection occurred in individuals who received BNT162b2 vaccine (PS weighted incidence rate: 3.65 per 1000 person-months), and 31,611 SARS-CoV-2 infection occurred in those who received ChAdOx1 nCoV-19 vaccine (PS weighted incidence rate: 5.25 per 1000 person-months). The time-stratified PS weighted rate difference of SARS-CoV-2 infection for BNT162b2 group vs. ChAdOx1 nCoV-19 group was -1.60 per 1000 person-months (95% confidence interval [CI]: -1.76 to -1.43 per 1000 person-months), and the hazard ratio was 0.69 (95% CI: 0.68 to 0.71). The results were similar across the stratum of sex, age (

Abstract Since its initial detection in Brazil in February 2020, SARS-CoV-2 and the associated COVID-19 pandemic have continued to devastate Latin America. Specific comorbidities, as well as sociodemographic and lifestyle factors that may be more prevalent in underserved areas, have been identified as risk factors for COVID-19 infection or associated adverse outcomes. Dynamics of infections and deaths in Latin America have varied by country and temporally, as has SARS-CoV-2 variant prevalence; however, more recently, the Delta and subsequent Omicron variants have become ubiquitous. Successful pandemic responses have involved robust infection mitigation measures, testing, and smart deployment of healthcare resourcing. While in some Latin American countries up to 90% of the population is fully vaccinated (i.e., 2 doses) against COVID-19, other countries have failed to reach the World Health Organization’s 70% target. Continued focus on comprehensive surveillance, strategies to maximize vaccine availability and uptake, and mitigation of collateral damage on other aspects of public health and social services are critical for managing the COVID-19 pandemic. This review summarizes the COVID-19 experience in Latin America, including epidemiology and vaccination. Key learnings and future considerations for the ongoing pandemic response are also discussed.

Key Clinical Message Immune thrombocytopenic purpura (ITP) is an autoimmune disease characterized by a low platelets count. In this paper, we present a case of ITP relapse in a 31‐year‐old Iranian woman as a potential complication of the AstraZeneca vaccine.

ABSTRACT Introduction: The immune response to different Coronavirus Disease 2019 (COVID-19) vaccines is under-investigated in end-stage kidney disease (ESKD) patients, especially in the Middle East and North Africa. We carried out this research to estimate the effectiveness of COVID-19 immunization in ESKD patients on regular hemodialysis (HD). Methods: In this prospective observational study, we enrolled 60 ESKD patients on regular HD who had completed COVID-19 vaccination and 30 vaccinated healthy participants. Serum levels of severe acute respiratory syndrome coronavirus 2 immunoglobulin G (SARS-COV2 IgG) were quantified 1 month after completing the vaccination schedule, and all participants were followed up from October 2021 to March 2022. The vaccines used in the study were from Pfizer-BioNTech, AstraZeneca, and Sinopharm. Results: The median level of SARS-COV2 IgG was lower in HD patients than in healthy participants (p < 0.001). Regarding the type of COVID-19 vaccination, there was no statistical difference in SARS-COV2 IgG levels among HD patients. During the observation period, none of the HD patients had COVID-19. Conclusion: COVID-19 vaccination appeared to be protective in HD patients for 6 months and the side effects of vaccines were tolerable.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) increases mortality rates in older adults and those with comorbidities. Individuals with certain comorbidities may have a poor immune response and require early booster vaccines. We aimed to assess the immune response after two doses of ChAdOx1 nCoV-19 vaccine, at 84-day intervals, in participants with the following comorbidities; diabetes mellitus; obesity; cardiovascular disease; chronic kidney disease; rheumatological disease; cirrhosis; hematological disease; hematological malignancy; or solid malignancy. The study was conducted at Chulabhorn Hospital in Thailand, with healthy healthcare workers serving as the control group. Of the 769 participants, 352 were in the healthy cohort and 417 were in the comorbidity cohort, all received at least one dose of vaccine. Anti-RBD total antibody levels were evaluated on Day 0, Day 84, and Day 112. The results at Day 112 (4 weeks after the second dose) showed that individuals with comorbidities had a poor immune response compared to healthy individuals, especially those with hematological malignancy and solid malignancy. The geometric mean concentration (GMC) of anti-RBD antibody in the comorbidity cohort was significantly lower than that in the healthy cohort: 433.66 BAU/ml (95% CI 334.62–562.01) versus 1096.14 BAU/ml (95% CI 1010.26–1189.33), respectively. The geometric mean ratio (GMR) between the two cohorts was 0.40 (95% CI 0.30–0.52, p

Recent studies have shown that in individuals who have received two doses of COVID-19 vaccine, the level of IgG antibodies decreased over time. In addition, the resurgence of the epidemic due to variants has led the authorities in several countries, including Morocco, to extend the third dose to the entire adult population. In this study, we included 43 healthcare workers (HCWs) who were vaccinated with three doses. They were vaccinated with ChAdOx1 nCoV-19 for the first two doses and with BNT 162b2 or BBIBP-CorV vaccine for the third dose. Humoral response was assessed on the day of injection of the third dose of vaccine and one month after the third dose by measuring anti-receptor-binding domain (RBD) IgG levels. Seven months after the second dose, the median titer of anti-RBD IgG was higher in the group with a history of SARS-CoV-2 infection than in the group with no history of infection (1038 AU/mL vs. 76.05 AU/mL, respectively, p = 0.003). One month after the third dose, a significant increase in median level of anti-RBD in both groups was observed: from 76.05 AU/mL to 6127 AU/mL in the group with no history of infection and from 1038 AU/mL to 14,412 AU/mL in the group with history of infection. Notably, the BNT 162b2 vaccine elicits a high titer of anti-RBD antibody compared to the BBIBP-CorV vaccine. Median antibody titers were 21,991 AU/mL and 3640 AU/mL for BNT 162b2 and BBIBP-CorV vaccines, respectively (p = 0.0002). 23% of HCWs were infected with SARS-CoV-2 within the first two months after the third dose injection. However, all these patients developed mild symptoms and tested negative by RT-qPCR between 10 and 15 days after the onset of symptoms. Our findings support that the third dose of COVID-19 vaccine significantly improves the humoral response and protects against the severe disease.

• AZD1222 was well tolerated and immunogenic in Japanese adults across age subgroups. • Overall, humoral responses against SARS-CoV-2 steadily declined over time. • At Day 365, anti-spike and receptor-binding domain titers were above Day 15 levels. • Neutralizing antibody titers declined to below detection in most participants. Long duration trial data for two-dose COVID-19 vaccines primary series' are uncommon due to unblinding and additional doses. We report one-year follow-up results from a phase 1/2 trial of AZD1222 (ChAdOx1 nCoV-19) in Japan. Adults (n = 256) seronegative for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) were stratified by age, 18–55 (n = 128), 56–69 (n = 86) and ≥70-year-old (n = 42), and randomized 3:1 to AZD1222 or placebo. Safety, immunogenicity, and exploratory efficacy data were collected until study Day 365. Safety was consistent with previous reports. In AZD1222 vaccinees, humoral responses against SARS-CoV-2 steadily declined over time. By Day 365, anti-SARS-CoV-2 spike-binding (spike) and receptor-binding domain (RBD) mean antibody titers remained above Day 15 levels and pseudovirus neutralizing antibodies were undetectable in many participants. AZD1222 is immunogenic and well tolerated in Japanese adults. Expected waning in anti-SARS-CoV-2 humoral responses was observed; spike and RBD antibody titers remained elevated. (ClinicalTrials.gov : NCT04568031). [ABSTRACT FROM AUTHOR]

Background & objectives: Vaccination and natural infection can both augment the immune responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but how omicron infection has affected the vaccine-induced and hybrid immunity is not well studied in Indian population. The present study was aimed to assess the durability and change in responses of humoral immunity with age, prior natural infection, vaccine type and duration with a minimum gap of six months post-two doses with either ChAdOx1 nCov-19 or BBV152 prior- and post-emergence of the omicron variant. Methods: A total of 1300 participants were included in this observational study between November 2021 and May 2022. Participants had completed at least six months after vaccination (2 doses) with either ChAdOx1 nCoV-19 or an inactivated whole virus vaccine BBV152. They were grouped according to their age (= or =60 yr) and prior exposure of SARS-CoV-2 infection. Five hundred and sixteen of these participants were followed up after emergence of the Omicron variant. The main outcome was durability and augmentation of the humoral immune response as determined by anti-receptor-binding domain (RBD) immunoglobulin G (IgG) concentrations, anti-nucleocapsid antibodies and anti-omicron RBD antibodies. Live virus neutralization assay was conducted for neutralizing antibodies against four variants - ancestral, delta and omicron and omicron sublineage BA.5. Results: Before the omicron surge, serum anti-RBD IgG antibodies were detected in 87 per cent participants after a median gap of eight months from the second vaccine dose, with a median titre of 114 [interquartile range (IQR) 32, 302] BAU/ml. The levels increased to 594 (252, 1230) BAU/ml postomicron surge (P<0.001) with 97 per cent participants having detectable antibodies, although only 40 had symptomatic infection during the omicron surge irrespective of vaccine type and previous history of infection. Those with prior natural infection and vaccination had higher anti-RBD IgG titre at baseline, which increased further [352 (IQR 131, 869) to 816 (IQR 383, 2001) BAU/ml] (P<0.001). The antibody levels remained elevated after a mean time gap of 10 months, although there was a decline of 41 per cent. The geometric mean titre was 452.54, 172.80, 83.1 and 76.99 against the ancestral, delta, omicron and omicron BA.5 variants in the live virus neutralization assay. Interpretation & conclusions: Anti-RBD IgG antibodies were detected in 85 per cent of participants after a median gap of eight months following the second vaccine dose. Omicron infection probably resulted in a substantial proportion of asymptomatic infection in the first four months in our study population and boosted the vaccine-induced humoral immune response, which declined but still remained durable over 10 months. [ABSTRACT FROM AUTHOR]

Vaccines are crucial for controlling the COVID-19 pandemic, and booster doses are becoming increasingly important. This study aimed to assess the efficacy of the ChAdOx1 nCoV-19 vaccine from AstraZeneca as a third dose in healthcare workers at different time intervals (one, three, and six months). Two methods to measure immune response—ELISA (EUROIMMUN Medizinische Labordiagnostika AG, Luebeck, Germany) and ELISpot (Mabtech AB, Macka Strand, Sweden)—were used. A total of 170 participants were included in the study. The results showed that while IgG levels decreased at six months compared to levels at one and three months, they were still significantly higher than the baseline. Furthermore, neutralizing levels at three and six months and after the third dose were not significantly different. These findings suggest that the immune response induced by the vaccine was robust and effective for several months. These results have significant implications for public health policymakers, as they provide strong support for booster vaccinations. The ChAdOx1 nCoV-19 vaccine appears to be a reliable option for preventing the spread of COVID-19, and this study provides valuable information for healthcare workers and policymakers in managing the pandemic. [ABSTRACT FROM AUTHOR]

• COVID-19 vaccine efficacy (VE) varies against SARS-CoV-2 variants of concern. • We present a final VE analysis from a phase 1b/2 AZD1222 trial in South Africa. • VE was 90% for WT, 6.7% for Beta and 77.1% for Delta ≥ 9 months post-vaccination. • Safety was consistent with the interim analysis and no new concerns were reported. • AZD1222 offers durable protection, potentially due to anamnestic immune responses. COVID-19 vaccine efficacy (VE) has been observed to vary against antigenically distinct SARS-CoV-2 variants of concern (VoC). Here we report the final analysis of VE and safety from COV005: a phase 1b/2, multicenter, double-blind, randomized, placebo-controlled study of primary series AZD1222 (ChAdOx1 nCoV-19) vaccination in South African adults aged 18–65 years. South Africa's first, second, and third waves of SARS-CoV-2 infections were respectively driven by the ancestral SARS-CoV-2 virus (wild type, WT), and SARS-CoV-2 Beta and Delta VoCs. VE against asymptomatic and symptomatic infection was 90.6% for WT, 6.7% for Beta and 77.1% for Delta. No cases of severe COVID-19 were documented ahead of unblinding. Safety was consistent with the interim analysis, with no new safety concerns identified. Notably, South Africa's Delta wave occurred ≥ 9 months after primary series vaccination, suggesting that primary series AZD1222 vaccination offers a good durability of protection, potentially due to an anamnestic response. Clinical trial identifier: CT.gov NCT04444674. [ABSTRACT FROM AUTHOR]

This study investigated the immunogenicity of, and reactogenicity to, the ChAdOx1 nCoV-19 vaccine according to pre-existing adenovirus immunity. Individuals scheduled for COVID-19 vaccination were prospectively enrolled in a tertiary hospital with 2400 beds from March 2020 onwards. Pre-existing adenovirus immunity data was obtained before ChAdOx1 nCoV-19 vaccination. A total of 68 adult patients administered two doses of the ChAdOx1 nCoV-19 vaccine were enrolled. Pre-existing adenovirus immunity was identified in 49 patients (72.1%), but not in the remaining 19 patients (27.9%). The geometric mean titer of S-specific IgG antibodies was statistically higher in individuals without pre-existing adenovirus immunity at several time points: before the second ChAdOx1 nCoV-19 dose (56.4 (36.6–125.0) vs. 51.0 (17.9–122.3), p = 0.024), 2–3 weeks after the second ChAdOx1 nCoV-19 dose (629.5 (451.5–926.5) vs. 555.0 (287.3–926.0), p = 0.049), and 3 months after the second ChAdOx1 nCoV-19 dose (274.5 (160.5–655.3) vs. 176.0 (94.3–255.3), p = 0.033). In the absence of pre-existing adenovirus immunity, systemic events were observed with higher frequency, especially chills (73.7% vs. 31.9%, p = 0.002). In conclusion, individuals without pre-existing adenovirus immunity showed a higher immune response to ChAdOx1 nCoV-19 vaccination and a higher frequency of reactogenicity to ChAdOx1 nCoV-19 vaccination was observed. [ABSTRACT FROM AUTHOR]

ABSTRACT: Objectives: SARS-CoV-2 is primarily transmitted within households, with massive healthcare system burdens. The role of inactivated vaccines and ChAdOx1 nCoV-19 vaccination in the prevention of within-household transmission remains unknown. Methods: This observational case-control study tracked 408 SARS-CoV-2 polymerase chain reaction–confirmed index cases from April to September 2021. This study aimed to prove the benefit of inactivated and ChAdOx1 nCoV-19 vaccinated index cases in preventing within-household transmissibility. Results: A total of 1178 household contacts were investigated. A total of 231 index cases were vaccinated with inactivated or ChAdOx1 nCoV-19 vaccine, and 177 were unvaccinated. The vaccinated index cases exhibited a 7.8% risk reduction in household transmission. There was no difference in the secondary attack rate of 50.77% in unvaccinated cases compared with 46.81% in vaccinated index cases (P-value = 0.177). Those who completed the two-dose SARS-CoV-2 vaccination demonstrated a 93% reduction in household transmissibility within 14-90 days. The effectiveness for preventing household transmission was 26.09%. The 87% reduced risk of household transmissibility was observed among those who wore masks. Conclusion: The completed two-dose SARS-CoV-2 inactivated and ChAdOx1 nCoV-19 vaccination within 14-90 days among index cases demonstrated benefits in preventing within-household transmissibility. Implementing high-efficacy vaccination and an appropriate booster dose can prevent household transmission.

We present a fatal case of cerebral arterial thrombosis after corona virus disease 19 (COVID-19) vaccination with ChAdOx1 nCOV-19. The deceased was a 63-year-old woman with no relevant medical history. She presented symptoms of nausea, fatigue, and headache immediately after vaccination. Ten days after vaccination, she suddenly started vomiting and developed high blood pressure. The patient eventually died 23 days after vaccination. Autopsy findings showed that the cerebral arteries and internal carotid arteries were fully enlarged and were compacted with thrombi. The brain stem showed ischemic necrosis, and extravasation from this necrotic lesion led to focal subarachnoid hemorrhage around the brain stem where large blood clots still remained. No aneurysms or atherosclerotic changes were found in these arteries. We note the following three facts. Firstly, all symptoms occurred immediately after vaccination; secondly, the main cause of death was consistent with known side effects of the vaccine; and lastly, the mechanism of thrombus formation in this case goes beyond the general category of thrombogenesis known so far. While the authors know that this case does not fall into known categories of vaccine side effects, we presenting this case to demonstrate that a comprehensive review of various possibilities related to vaccine side effects is needed to establish a COVID-19 defense system.

Objective: Unusual clinical course Background: Thrombosis with thrombocytopenia syndrome (TTS), including vaccine-induced immune thrombotic thrombocytopenia (VITT), is an extremely rare adverse effect, mostly seen after initial vaccination with the viral vectorbased AstraZeneca-Oxford COVID-19 vaccine. It is characterized by mild to severe thrombocytopenia and venous or arterial thrombosis. Case Report: Herein, we present a case of an 18-year-old male patient who developed Level 1 TTS (probable VITT) eight days after immunization with the ChADOx1 nCOV-19 vaccine (Covishield; AZ-Oxford). Initial investigations revealed severe thrombocytopenia, hemiparesis, and intracranial hemorrhage, after which the patient was treated conservatively. However, a decompressive craniotomy was performed later due to patient deterioration. One week after surgery, the patient developed bilious vomiting, lower-gastrointestinal bleeding, and abdominal distension. An abdominal CT scan was performed that showed thrombosis of the portal vein with occlusion of the left iliac vein. The patient underwent an exploratory laparotomy followed by resection and anastomosis of the small bowel due to massive gut gangrene. Due to persistent thrombocytopenia after surgery, intravenous immune globulin (IVIG) was administered. The platelet count increased thereafter, and the patient stabilized. He was discharged on the 33rd day after admission and was followed up for a year. No post-hospitalization complications were observed in the follow-up period. Conclusions: Although vaccines have been proven to be highly safe and effective to end the Coronavirus Disease 2019 (COVID-19) caused pandemic, there is still a small risk of developing rare complications, including TTS and VITT. Early diagnosis and prompt intervention are key for patient management. [ABSTRACT FROM AUTHOR]

There are limited data on the rates of the waning of antibody levels after two-dose and booster vaccination according to the different platforms of COVID-19 vaccines. We enrolled healthcare workers (HCWs) in a tertiary care hospital who received homologous two-dose vaccination, followed by a homologous or heterologous booster mRNA vaccine. SARS-CoV-2 S1-specific IgG was measured using ELISA. A linear mixed regression model was used to compare the slope from the peak antibody titre to the lowest antibody titres 3 months after vaccination. A total of 113 HCWs (BNT162b2 (n = 48 [42%]), ChAdOx1 nCoV-19 (n = 52 [46%]) or mRNA-1273 (n = 13 [12%])) were enrolled in this prospective cohort study. More gradual antibody waning was observed over 3 months with the two-dose ChAdOx1 nCoV-19 (ChAdOx1) than with the two-dose BNT162b2 or mRNA-1273 (p < 0.001 and p = 0.001, respectively). In addition, homologous mRNA-1273 booster induced a more durable antibody response than homologous BNT162b2 booster (p < 0.001) or heterologous ChAdOx1-BNT162b2 booster (p < 0.001). Two-dose homologous ChAdOx1 vaccination or homologous mRNA-1273 booster appears to induce more-durable antibody responses than 2-dose homologous mRNA vaccination, homologous BNT162b2 booster, or 2-dose ChAdOx1 followed by BNT62b2 booster, although our findings are based on the relatively short term (3-month) follow-up after the vaccinations and the evaluation of the slopes from different antibody peak levels. Further studies on long-term durability depending on the types of vaccines are needed. [ABSTRACT FROM AUTHOR]

To facilitate interpretation of clinical SARS-CoV-2 anti-spike IgG analyses post-vaccination, 82 healthcare workers were followed through three vaccination-regimens: two regimens were comprised of two doses of BNT162b2 three or six weeks apart, followed by a dose of mRNA-vaccine, and in the other regimen, the first dose was replaced by ChAdOx1 nCov-19. After each dose, anti-spike IgG was compared between regimens. As many participants became infected, anti-spike IgG persistence was compared between infected and uninfected participants. Thirteen to twenty-one days after the first dose, seroconversion, and the median anti-spike IgG level in the ChAdOx1 group was significantly lower than in the BNT162b2 groups (23 versus 68 and 73 AU/mL). The second dose caused a significant increase in anti-spike IgG, but the median level was lower in the BNT162b2-short-interval group (280 AU/mL), compared to the BNT162b2-long-interval (1075 AU/mL) and ChAdOx1 (1160 AU/mL) group. After the third dose, all groups showed increases to similar anti-spike IgG levels (2075–2390 AU/mL). Over the next half year, anti-spike IgG levels declined significantly in all groups, but appeared to persist longer after post-vaccination infection. This is the first three-dose study with one dose of ChAdOx1. Despite initial differences, all vaccine regimens gave similarly high antibody levels and persistence after the third dose. [ABSTRACT FROM AUTHOR]

ChAdOx1 nCoV-19 (AZD1222) is a replication-deficient chimpanzee adenovirus vectored vaccine developed by Oxford and AstraZeneca for a disease we all know as Coronavirus, or COVID-19. Ongoing clinical studies reveal that the ChAdOx1 nCoV-19 vaccine has a tolerable safety profile and is effective against symptomatic COVID-19. This vaccine may prove crucial in boosting herd immunity, averting life threatening illness, and relieving the current pandemic. In this mini review, we performed a thorough literature search through PubMed and Google Scholar and reported various case reports associated with complications of the adenovirus-vectored COVID-19 vaccine. Various adverse effects of the ChAdOx1 nCoV-19 vaccine were reported around the globe, which were often serious but rare and developed into life-threatening pathologies such as GBS, thrombocytopenia, demyelinating neuropathies, progressive dementia, cerebral infarction, IgA vasculitis, hemophagocytic lymphohistiocytosis, herpes zoster, cutaneous reactions, and vein thrombosis. These worldwide reported complications, which are usually rare and severe, will aid clinicians in understanding and managing unforeseen situations. There is a need for more research to find out more about these complications and their etiopathogenesis. However, the benefits of these vaccinations for stopping the spread of the outbreak and lowering the fatality rate outweigh the potential risk of the uncommon complications. [ABSTRACT FROM AUTHOR]

Patients with autoimmune rheumatic diseases with a previous infection by the SARS-CoV-2 virus have exaggerated responses to a single dose of COVID-19 vaccination as compared to fully vaccinated infection naive patients. The second dose is currently recommended at an extended gap after the infection, but the information available regarding response to the second dose in this subgroup is limited. Patients with AIRDs previously infected with COVID-19, who have received at least one dose of AZD1222/ChAdOx1 (n = 200) were included and stratified based on vaccine doses (V), and infection (I) into I + V, I + V + V, V + I, V + V + I. Anti-RBD (receptor binding domain) antibodies were compared across the four groups. In 49 patients of the I + V + V group (AZD12222), paired sera were compared for antibody levels and neutralization after each vaccine dose. Thirty patients with hybrid immunity after BBV152 and 25 with complete vaccination without infection were included as controls. The highest anti-RBD antibody levels were observed in the V + V + I group (18,219 ± 7702 IU/ml) with statistically similar titers in the I + V + V (10,392 ± 8514 IU/ml) and the I + V (8801 ± 8122 IU/ml). This was confirmed in the 49 paired samples that paradoxically showed a lowering of antibody titers after the second dose [9626 (IQR: 4575–18,785)–5781 (2484–11,906); p < 0.001]. Neutralization of the Delta variant was unaffected but Omicron neutralization was significantly reduced after the second dose [45.7 (5.3–86.53)–35% (7.3–70.9); p = 0.028]. Ancillary analyses showed that only the hybrid immune sera could neutralize the Omicron variant and AZD1222 hybrids performed better than BBV152 hybrids. The second dose of AZD1222 did not boost antibody titers in patients with RD who had COVID-19 previously. In the analysis of paired sera, the second dose led to a statistically significant reduction in antibody titers and also reduced neutralization of the Omicron variant. [ABSTRACT FROM AUTHOR]

More than 600 healthcare workers died due to COVID-19 infection until January 2022 in Ecuador. Even though the COVID-19 vaccines are safe, local and systemic reactions were reported among physicians. This study aims to analyze the adverse events of COVID-19 with an emphasis on comparing the homologous and heterologous booster doses in physicians that received three approved vaccines in Ecuador. An electronic survey was performed in Quito, Ecuador, directed at physicians who were vaccinated with the three doses of COVID-19 vaccines. A total of 210 participants were analyzed after administering any dose of the vaccines. At least one AE was identified in 60.0% (126/210) of the sample after the first dose, 52.40% (110/210) after the second dose, and 75.2% (158/210) after the booster dose. The most frequent AEs were localized pain, myalgia, headache, and fever. At least one drug was used in 44.3% of the population after the first dose, 37.1% after the second dose, and 63.8% in the booster dose. Heterologous booster produces more AEs compared with homologous booster (80.1% vs. 53.8%), and 77.3% of participants reported that interfered with daily activities. Similar studies agree that reactogenicity occurs mainly with heterologous vaccination compared to homologous vaccination. This situation affected physicians' performance in daily activities and led them to use medication for the symptoms. In the future, it is recommended to perform cohort studies, where adverse events that are associated with vaccine boosters in the general population can be analyzed longitudinally, thus improving the level of evidence of the results. [ABSTRACT FROM AUTHOR]

Background: Both BNT162b2 (Pfizer–BioNTech) and ChAdOx1 nCoV-19 (Oxford–AstraZeneca) vaccines have shown high efficacy against COVID-19 in randomized controlled trials. However, their comparative effectiveness against COVID-19 is unclear in the real world. We evaluated the comparative effectiveness of the BNT162b2 and ChAdOx1 nCoV-19 vaccines against COVID-19 in the UK general population. Methods: We emulated a target trial using IQVIA Medical Research Database (IMRD), an electronic primary care database from the UK (2021). We included 1,311,075 participants, consisting of 637,549 men and 673,526 women age≥18 years, who received vaccination with BNT162b2 or ChAdOx1 nCoV-19 between January 1 and August 31, 2021. The outcomes consisted of confirmed diagnosis of SARS-CoV-2 infection, hospitalisation for COVID-19 and death from COVID-19 in the IMRD. We performed a cox-proportional hazard model to compare the risk of each outcome variable between the two vaccines adjusting for potential confounders with time-stratified overlap weighting of propensity score (PS). Results: During a mean of 6.7 months of follow-up, 20,070 confirmed SARS-CoV-2 infection occurred in individuals who received BNT162b2 vaccine (PS weighted incidence rate: 3.65 per 1000 person-months), and 31,611 SARS-CoV-2 infection occurred in those who received ChAdOx1 nCoV-19 vaccine (PS weighted incidence rate: 5.25 per 1000 person-months). The time-stratified PS weighted rate difference of SARS-CoV-2 infection for BNT162b2 group vs. ChAdOx1 nCoV-19 group was -1.60 per 1000 person-months (95% confidence interval [CI]: -1.76 to -1.43 per 1000 person-months), and the hazard ratio was 0.69 (95% CI: 0.68 to 0.71). The results were similar across the stratum of sex, age (<65 and ≥65 years), and study periods (i.e., alpha-variant predominance period and delta-variant predominance period). The PS weighted incidence of hospitalisation for COVID-19 was also lower in the BNT162b2 vaccine group than that in the ChAdOx1 vaccine group (RD: -0.09, 95%CI: -0.13 to -0.05 per 1000 person-months; HR: 0.65, 95%CI: 0.57 to 0.74). No significant difference in the risk of death from COVID-19 was observed between the two comparison groups. Conclusions: In this population-based study, the BNT162b2 vaccine appears to be more efficacious than the ChAdOx1 nCoV-19 vaccine against SARS-CoV-2 infection and hospitalisation for COVID-19 but not death from COVID-19. [ABSTRACT FROM AUTHOR]

Since its initial detection in Brazil in February 2020, SARS-CoV-2 and the associated COVID-19 pandemic have continued to devastate Latin America. Specific comorbidities, as well as sociodemographic and lifestyle factors that may be more prevalent in underserved areas, have been identified as risk factors for COVID-19 infection or associated adverse outcomes. Dynamics of infections and deaths in Latin America have varied by country and temporally, as has SARS-CoV-2 variant prevalence; however, more recently, the Delta and subsequent Omicron variants have become ubiquitous. Successful pandemic responses have involved robust infection mitigation measures, testing, and smart deployment of healthcare resourcing. While in some Latin American countries up to 90% of the population is fully vaccinated (i.e., 2 doses) against COVID-19, other countries have failed to reach the World Health Organization's 70% target. Continued focus on comprehensive surveillance, strategies to maximize vaccine availability and uptake, and mitigation of collateral damage on other aspects of public health and social services are critical for managing the COVID-19 pandemic. This review summarizes the COVID-19 experience in Latin America, including epidemiology and vaccination. Key learnings and future considerations for the ongoing pandemic response are also discussed. [ABSTRACT FROM AUTHOR]

Mycobacterium-w (Mw) was shown to boost adaptive natural killer (ANK) cells and protect against COVID-19 during the first wave of the pandemic. As a follow-up of the trial, 50 healthcare workers (HCW) who had received Mw in September 2020 and subsequently received at least one dose of ChAdOx1 nCoV-19 vaccine (Mw + ChAdOx1 group) were monitored for symptomatic COVID-19 during a major outbreak with the delta variant of SARS-CoV-2 (April–June 2021), along with 201 HCW receiving both doses of the vaccine without Mw (ChAdOx1 group). Despite 48% having received just a single dose of the vaccine in the Mw + ChAdOx1 group, only two had mild COVID-19, compared to 36 infections in the ChAdOx1 group (HR-0.46, p = 0.009). Transcriptomic studies revealed an enhanced adaptive NK cell-dependent ADCC in the Mw + ChAdOx1 group, along with downregulation of the TLR2-MYD88 pathway and concomitant attenuation of downstream inflammatory pathways. This might have resulted in robust protection during the pandemic with the delta variant. [ABSTRACT FROM AUTHOR]

Background: Countries around the world are now racing to vaccinate people against SARS-CoV-2, the virus that causes COVID-19.The Government of India also rolled out its vaccination drive from 16th January '2021. Aims: To estimate the antibody response of the COVID-19 vaccine in the form of SARS-COV-2 IgG antibodies in vaccinated healthcare workers. Methods: Prospective follow-up was study conducted on healthcare workers (HCWs) of a Medical college in Dehradun, Uttarakhand. Healthcare workers who have been vaccinated for COVID-19 were tested for SARS-CoV-2-IgG antibodies at regular intervals i.e at 4 weeks after the 1st dose and then again at 4 weeks after the 2nd dose. The third sample was taken 6 months after the 2nd dose. Results: A total of 302 HCWs were enrolled in the study who gave their samples for IgG antibody estimation after the covishield vaccine. After 4 weeks of completion of both doses, 96% HCWs formed SARS-COV-2 IgG antibodies, whereas 4% didn't. Then after 6 months of follow-up, 14% HCWs have become negative for antibodies and better immunity is seen in people who also got infected with COVID-19 during this time. Conclusion: This study concludes that the immunity gained after vaccination is waning off in around 6 months and there is a need for a booster dose, especially for people at high risk. The infection control practices still play a crucial role in the prevention of this deadly disease. [ABSTRACT FROM AUTHOR]

Many available SARS-CoV-2 vaccines demonstrated good humoral response, but studies directly comparing their immunogenicity in the general population are lacking. We evaluated the medium–term kinetics of anti-S SARS-CoV-2 antibodies (Abs) at one and six months after the second dose of BNT162b2, BBIBP-CorV, and Gam-COVID-Vac. Immunogenicity at six months was directly compared between BNT162b2, BBIBP-CorV, Gam-COVID-Vac, and ChAdOx1 nCoV-19. Participants ≥ 20 years old from Novi Sad, Serbia, without prior SARS-CoV-2 infection, were included. Anti S1/S2 IgG antibodies were measured using quantitative LIAISON SARS-CoV-2 assay. A total of 368 participants were included: 231 (62.77%) had sera collected at two time points. Two doses of BNT162b2 were received by 37.50% of participants, followed by BBIBP-CorV (22.01%), Gam-COVID-Vac (21.47%), and ChAdOx1 nCoV-19 (19.02%). Mean Ab levels at the 28th day and 6 months were 216.55 (SD = 105.73) AU/mL and 75.68 (SD = 57.30) for BNT162b2, 194.38 (SD = 140.24) and 90.53 (SD = 111.30) for Gam-COVID-Vac, and 72.74 (SD = 80.04) and 24.43 (SD = 38.43) for BBIBP-CorV group (p < 0.01, between two time points across all three groups), with a significant difference between women and men (p < 0.01, for both sexes). At the sixth month post-vaccination, the highest mean Ab level was detected in Gam-COVID-Vac group (91.28 AU/mL, SD = 95.96), followed by BNT162b2 (85.25 AU/mL, SD = 60.02), ChAdOx1 nCoV-19 (64.22 AU/mL, SD = 65.30), and BBIBP-CorV (25.26 AU/mL, SD = 36.92) (p < 0.01). Anti-spike IgG persistence was demonstrated six months post-vaccination with a significant decline in Ab levels. These results suggest a lower protection against SARS-CoV-2 over time. Our findings support the introduction of additional (booster) doses. [ABSTRACT FROM AUTHOR]

Background: The pandemic unleashed by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected more than 500 million people worldwide and caused more than 6 million deaths. Cellular and humoral immunity induced by infection or immunization are key factors in controlling the viral burden and avoiding the recurrence of coronavirus disease. The duration and effectiveness of immunity after infection is relevant to pandemic policy interventions, including the timing of vaccine boosters. Objectives: We sought to evaluate longitudinal binding and functional antibodies against SARS-CoV-2 receptor-binding domain in police officers and health care workers with a history of coronavirus disease 2019 and compare with SARS-CoV-2–naive individuals after vaccination with adenovirus-based ChAdOx1 nCoV-19 (AstraZeneca-Fiocruz) or the inactivated CoronaVac vaccine (Sinovac-Butantan Institute). Methods: A total of 208 participants were vaccinated. Of these, 126 (60.57%) received the ChAdOx1 nCoV-19 vaccine and 82 (39.42%) received the CoronaVac vaccine. Prevaccination and postvaccination blood was collected, and the amount of anti–SARS-CoV-2 IgG and the neutralizing ability of the antibodies to block the interaction between angiotensin-converting enzyme 2 and receptor-binding domain were determined. Results: Subjects with preexisting SARS-CoV-2 immunity and who received a single dose of ChAdOx1 nCoV-19 or CoronaVac have similar or superior antibody levels when compared with levels in seronegative individuals even after 2 doses of the vaccine. Neutralizing antibody titers of seropositive individuals were higher with a single dose of either ChAdOx1 nCoV-19 or CoronaVac compared with those of seronegative individuals. After 2 doses, both groups reached a plateau response. Conclusions: Our data reinforce the importance of vaccine boosters to increase specific binding and neutralizing SARS-CoV-2 antibodies.