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Introduction: This study examines the efficacy and safety of three COVID-19 booster vaccines including mRNA-based vaccines (BNT162b2 (BioNTech/Pfizer) and/or mRNA-1273 (Moderna)), Non-Replicating Viral-Vector vaccines (ChAdOx1 nCoV-19 vaccine (AstraZeneca) and/or Ad26. COV2.S (Johnson & Johnson)), and Protein Subunit vaccine (SpikoGen) in immunosuppressed patients. Methods: Relevant articles were systematically searched using medical subject heading (MeSH) and keywords “COVID‐19” and “booster dose” or “booster vaccine” or ‘’fourth dose” in the online databases of PubMed, Embase, Scopus, and Web of Science. To identify eligible studies, a two-phase screening process was implemented. Initially, three researchers evaluated the studies based on the relevancy of the title and abstract. Results: A total of 58 studies met the inclusion criteria and were included in this review. The findings suggest that booster doses offer greater protection against the disease than the primary dose. The study also compared various vaccine types, revealing that viral vector and nucleic acid vaccines outperformed inactivated vaccines. Results indicated that individuals receiving booster doses experienced superior outcomes compared to those without boosters. Vaccination against COVID-19 emerged as the most effective preventive measure against infection and symptom severity. Elevated antibody levels post-booster dose vaccination in the population signaled robust immune responses, underscoring the benefits of supplementary vaccine doses. Conclusion: This systematic review highlights preliminary evidence supporting the immunologic outcomes and safety of COVID-19 vaccine boosters in enhancing immune responses against SARS-CoV-2. However, further research is needed to determine optimal timing intervals between primary vaccination series and boosters while considering global equity issues and variant-specific considerations.

Introduction. Clinical evidence suggests that certain probiotics may help treat and prevent viral infections. To date, the effectiveness of probiotics in the alleviation of COVID-19 has not been established. The aim of this systematic review was to assess the role of probiotics in the prevention and treatment of COVID-19. Materials and methods. An extensive search of four electronic databases was performed which included Embase, Scopus, Web of Science, and PubMed from November 2019 to June 2022. After reviewing the references list of related articles additional studies were identified. A multiple combination of keywords validated by MESH were used to search the databases. Study selection was performed according to an inclusion and exclusion criteria. Results. Twenty-three articles met the study inclusion criteria. Six articles were conducted in vitro while the remaining studies were conducted in the human population (in vivo). The type of probiotic was defined in eighteen studies. There were two studies that used supplements (vitamins, herbals, minerals, etc.) in addition to probiotics. The largest sample size was 445 850 participants which were from a study that used an application-based survey. The majority of studies found that probiotics had a positive effect on the COVID-19 disease. The benefits included early remission of COVID-19 symptoms and a shorter duration of sickness (10 studies), lower mortality rates (3 studies), and decreased hospitalization and length of stay (3 studies). Six in vitro studies found that probiotics were beneficial against SARS-CoV-2 through antiviral effects. There were only two studies that found probiotics to be ineffective or caused negative effects when consumed in COVID-19 patients. Conclusion. Available evidence supports the antiviral role of probiotics on prevention and treatment of COVID-19. The antiviral potential of Lactobacillus paracasei metabolite PlnE and PlnF against SARS-CoV-2 may explain the effectiveness of probiotics on COVID-19.

Abstract Background and Aims Alteration in humans' gut microbiota was reported in patients infected with severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2). The gut and upper respiratory tract (URT) microbiota harbor a dynamic and complex population of microorganisms and have strong interaction with host immune system homeostasis. However, our knowledge about microbiota and its association with SARS‐CoV‐2 is still limited. We aimed to systematically review the effects of gut microbiota on the SARS‐CoV‐2 infection and its severity and the impact that SARS‐CoV‐2 could have on the gut microbiota. Methods We searched the keywords in the online databases of Web of Science, Scopus, PubMed, and Cochrane on December 31, 2021. After duplicate removal, we performed the screening process in two stages; title/abstract and then full‐text screening. The data of the eligible studies were extracted into a pre‐designed word table. This study adhered to the PRISMA checklist and Newcastle−Ottawa Scale Bias Assessment tool. Results Sixty‐three publications were included in this review. Our study shows that among COVID‐19 patients, particularly moderate to severe cases, the gut and lung microbiota was different compared to healthy individuals. In addition, the severity, and viral load of COVID‐19 disease would probably also be influenced by the gut, and lung microbiota's composition. Conclusion Our study concludes that there was a significant difference in the composition of the URT, and gut microbiota in COVID‐19 patients compared to the general healthy individuals, with an increase in opportunistic pathogens. Further, research is needed to investigate the probable bidirectional association of COVID‐19 and human microbiome.

Introduction: Rare serious complications have been documented after COVID-19 vaccination as clinical research proceeded and new target populations, such as children and ‎pregnant women, were included. In this study, we attempted to review the literature relevant to ‎pregnancy complications and maternal outcomes of COVID-19 immunization in pregnant women. ‎ Methods: We searched the databases of PubMed, Scopus, Cochrane, and Web of Science on 31 August 2022. The records were downloaded and underwent a two-step screening; 1) title/abstract and then 2) full-text screening to identify the eligible studies. We included English original studies that evaluated the adverse effects of COVID-19 vaccines during pregnancy. Information such as the type of ‎study, geographical location, type of vaccine injected, gestational age, maternal underlying diseases, and ‎complications following the vaccination were extracted into pre-designed tables. Results: According to the findings of included studies, in most of them vaccination had a positive impact and no negative effects were observed. Also, no medical history was reported in 11 articles, and pregnant women had no underlying diseases. Some serious adverse events were reported after ‎vaccination, including miscarriage, paresthesia, uterine contraction, vaginal bleeding, preterm birth, major ‎congenital anomalies, intrauterine growth restriction, and seizure. ‎ Conclusion: Because of limited data availability and the cross-sectional design of most studies, we could neither infer ‎causation between vaccines and incidence of adverse effects nor comment with certainty about any ‎possible adverse outcome of COVID-19 vaccines in vaccinated pregnant women. Consequently, more longitudinal and experimental studies are needed to define the exact adverse effects of COVID-19 vaccines in pregnant women.

Abstract Introduction Patients with COVID‐19 may present different viral loads levels. However, the relationship between viral load and disease severity in COVID‐19 is still unknown. Therefore, this study aimed to systematically review the association between SARS‐CoV‐2 viral load and COVID‐19 severity. Methods The relevant studies using the keywords of “COVID‐19” and “viral load” were searched in the databases of PubMed, Scopus, Google Scholar, and Web of Science. A two‐step title/abstract screening process was carried out and the eligible studies were included in the study. Results Thirty‐four studies were included from the initial 1015 records. The vast majority of studies have utilized real‐time reverse transcription‐polymerase chain reaction of the nasopharyngeal/respiratory swabs to report viral load. Viral loads were commonly reported either as cycle threshold (Ct) or log10 RNA copies/ml. Conclusion The results were inconclusive about the relationship between COVID‐19 severity and viral load, as a similar number of studies either approved or opposed this hypothesis. However, the studies denote the direct relationship between older age and higher SARS‐CoV‐2 viral load, which is a known risk factor for COVID‐19 mortality. The higher viral load in older patients may serve as a mechanism for any possible relationships between COVID‐19 viral load and disease severity. There was a positive correlation between SARS‐CoV‐2 viral load and its transmissibility. Nonetheless, further studies are recommended to precisely characterize this matter.