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Thailand incorporated the hepatitis B (HepB) vaccine into the infant combination vaccine known as pentavalent wP-containing vaccines (DTwP-HB-Hib) and hexavalent aP-containing vaccines (DTaP-IPV-HB-Hib). We followed healthy children from the clinical trial (ClinicalTrials.gov NCT02408926) in which children were randomly assigned to receive either pentavalent or hexavalent vaccines for their primary series (administered at 2, 4, and 6 months) and first booster vaccination (at 18 months), following the monovalent HepB vaccine at birth. Blood samples were collected to evaluate the persistence of hepatitis B surface antibody (anti-HBs) at 3, 4, 5, 6 and 7 years of age. The results showed that at 7 years of age, a higher percentage of children in the hexavalent group maintained anti-HBs levels ≥ 10 mIU/mL compared to those in the pentavalent group (86.9 % vs. 59.7 %). This study showed good persistence of anti-HBs among hexavalent-vaccinated children 5.5 years after the last dose of the HepB vaccine., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

As of 2024, Thailand has not incorporated the varicella-zoster virus (VZV) vaccine into the Expanded Program on Immunization (EPI). This study aimed to evaluate VZV seroprevalence across all age groups in Chonburi Province, Thailand, during the post-COVID-19 era, and to support the development of a vaccination plan against VZV. A total of 950 participants were enrolled from October 2022 to January 2023. VZV antibody levels were measured using ELISA kits (EUROIMMUN, Lübeck, Germany), with seropositivity set at ≥110 IU/L. The overall VZV seropositivity rate was 64.8%, similar to rates in 1994 and 2014. However, seropositivity rates for the 5-9, 10-14, and 15-19 age groups were significantly higher in the 1994 study, and for the 10-14 and 15-19 age groups in the 2014 study, indicating a declining trend among young Thai individuals. The seropositivity rate increased with age, with a seroprevalence exceeding 80% in individuals aged 30 years and older. Our study found a significant association between the history of varicella and seropositivity. Thus, a positive history may indicate immunity. In conclusion, a significant portion of Thai adolescents are still vulnerable to varicella, highlighting the crucial role of vaccination in averting serious illness.

Background: Several countries have authorized a booster vaccine campaign to combat the spread of COVID-19. Data on persistence of booster vaccine-induced immunity against new Omicron subvariants are still limited. Therefore, our study aimed to determine the serological immune response of COVID-19 booster after CoronaVac-priming., Methods: A total of 187 CoronaVac-primed participants were enrolled and received an inactivated (BBIBP), viral vector (AZD1222) or mRNA vaccine (full-/half-dose BNT162B2, full-/half-dose mRNA-1273) as a booster dose. The persistence of humoral immunity both binding and neutralizing antibodies against wild-type and Omicron was determined on day 90-120 after booster., Results: A waning of total RBD immunoglobulin (Ig) levels, anti -RBD IgG, and neutralizing antibodies against Omicron BA.1, BA.2, and BA.4/5 variants was observed 90-120 days after booster vaccination. Participants who received mRNA-1273 had the highest persistence of the immunogenicity response, followed by BNT162b2, AZD1222, and BBIBP-CorV. The responses between full and half doses of mRNA-1273 were comparable. The percentage reduction of binding antibody ranged from 50 % to 75 % among all booster vaccine., Conclusions: The antibody response substantially waned after 90-120 days post-booster dose. The heterologous mRNA and the viral vector booster demonstrated higher detectable rate of humoral immune responses against the Omicron variant compared to the inactivated BBIBP booster. Nevertheless, an additional fourth dose is recommended to maintain immune response against infection., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

This study investigated the impact of hybrid immunity on antibody responses in the participants who received two to seven doses of the COVID-19 vaccine. The study was conducted between April and June 2023. Out of 771 serum samples analyzed, 71.7% exhibited hybrid immunity (positive for total anti-N Ig), while 28.3% showed vaccine-induced immunity (negative for total anti-N Ig). Participants were categorized based on the number of vaccine doses: 2, 3, 4, and ≥5. The findings highlight a trend where a higher number of vaccine doses received was associated with a lower infection rate. There was no significant difference in total RBD Ig levels between those who received 3, 4, or ≥5 doses in both the hybrid immunity and vaccination alone groups across all observed durations as follows: <6 months, 6 to <9 months, 9 to <12 months, and ≥12 months. Hybrid immunity consistently maintained higher total RBD Ig levels and durability compared to vaccination alone, with estimated half-lives (T 1/2 ) of 189.5 days versus 106.8 days for vaccine alone. This investigation underscored the potential benefit of hybrid immunity and raised questions about the optimal strategies for further vaccine dosing.

Seroprevalence studies on SARS-CoV-2 are essential for estimating actual prevalence rates of infection and vaccination in communities. This study evaluated infection rates based on total anti-nucleocapsid immunoglobulin (N) and/or infection history. We determined the seroprevalence of anti-receptor binding domain (RBD) antibodies across age groups. A cross-sectional study was conducted in Chonburi province, Thailand, between October 2022 and January 2023. Participants included newborns to adults aged up to 80 years. All serum samples were tested for anti-N total Ig and anti-RBD IgG. The interviewer-administered questionnaires queried information on infection history and vaccination records. Of 1459 participants enrolled from the Chonburi population, ~ 72.4% were infected. The number of infections was higher in children aged < 5 years, with evidence of SARS-CoV-2 infection decreasing significantly with increasing age. There were no significant differences based on sex or occupation. Overall, ~ 97.4% of participants had an immune response against SARS-CoV-2. The anti-RBD IgG seroprevalence rate was lower in younger vaccinated individuals and was slightly increased to 100% seropositivity at ages > 60 years. Our findings will help predict the exact number of infections and the seroprevalence of SARS-CoV-2 in the Thai population. Furthermore, this information is essential for public health decision-making and the development of vaccination strategies., (© 2023. Springer Nature Limited.)

Objectives: To assess the binding antibody response and strength of neutralization against Omicron BA.5 in serum samples from children with different antigen exposures (infection/vaccination) and hybrid immunity., Methods: This study recruited children aged 5-7 years. All samples were tested for anti-nucleocapsid immunoglobulin (Ig)G, anti-receptor binding domain (RBD) IgG, and total anti-RBD Ig. Neutralizing antibodies (nAbs) against Omicron BA.5 were determined using a focus reduction neutralization test., Results: A total of 196 serum samples from unvaccinated children with infection (n = 57), vaccination alone (n = 71), and hybrid immunity (n = 68). Our results showed that 90% of the samples from children with hybrid immunity, 62.2% from two-dose vaccination, and 48% from Omicron infection alone had detectable nAbs against Omicron BA.5. The highest neutralizing titer was observed in infection plus two-dose vaccination, which reached 6.3-fold increase, whereas nAb titers in two-dose vaccination was comparable to Omicron-infected sera. However, sera from pre-Omicron infection and single-dose vaccination failed to neutralize Omicron BA.5; although, the total anti-RBD Ig were comparable with Omicron-infected sera., Conclusion: This result highlights that hybrid immunity provided cross-reactive antibodies to neutralize Omicron BA.5 compared with either vaccination or infection alone. The finding emphasizes the importance of vaccination in unvaccinated children who are infected with pre-Omicron or Omicron variants., Competing Interests: Declarations of competing interest The authors have no competing interests to declare., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Coronavirus disease 2019 (COVID-19) is a contagious illness worldwide. While guidelines for the treatment of COVID-19 have been established, the understanding of the relationship among neutralizing antibodies, cytokines, and the combined use of antiviral medications, steroid drugs, and convalescent plasma therapy remains limited. Here, we investigated the connection between the immunological response and the efficacy of convalescent plasma therapy in COVID-19 patients with moderate-to-severe pneumonia. The study included a retrospective analysis of 49 patients aged 35 to 57. We conducted clinical assessments to determine antibody levels, biochemical markers, and cytokine levels. Among the patients, 48 (98%) were discharged, while one died. We observed significantly higher levels of anti-nucleocapsid, anti-spike, and neutralizing antibodies on days 3, 7, and 14 after the transfusion compared to before treatment. Serum CRP and D-dimer levels varied significantly across these four time points. Moreover, convalescent plasma therapy demonstrated an immunoregulatory effect on cytokine parameters, with significant differences in IFN-β, IL-6, IL-10, and IFN-α levels observed at different sampling times. Evaluating the cytokine signature, along with standard clinical and laboratory parameters, may help to identify the onset of a cytokine storm in COVID-19 patients and determine the appropriate indication for anti-cytokine treatment.

The Coronavirus disease 2019 (COVID-19) pandemic, caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), continues to surge despite the widespread use of vaccination. In Thailand, more than 77% and 39% of the population received two doses and three doses of COVID-19 vaccines as of December 2022, respectively. In addition, during the Omicron predominant period in 2022, more than 70% of Thai individuals have been infected. To gain comprehensive insight into SARS-CoV-2 antibody dynamics following vaccination or following vaccination and infection (hybrid immunity), we performed a cross-sectional analysis of sera samples from individuals who received COVID-19 vaccination and/or have been infected with COVID-19 in Thailand between January 2021 and December 2022. A total of 4126 samples were collected. Humoral immunity was evaluated by quantifying the immunoglobulin (including IgG, IgM, and IgA isotypes) specific to the SARS-CoV-2 receptor-binding domain (RBD) or Ig anti-RBD. The results showed that individuals who received two-dose vaccination alone had lower levels of Ig anti-RBD, which rapidly waned over time. To restore the waning antibody, a third dose vaccination is recommended for uninfected individuals who have only received 2 doses.

To compare the reactogenicity and immunogenicity between the two-dose mRNA COVID-19 vaccine regimen and one or two doses of inactivated vaccine followed by an mRNA vaccine regimen in healthy children between 5 and 11 years of age, a prospective cohort study was performed at King Chulalongkorn Memorial Hospital in Thailand between March to June 2022. Healthy children between 5 and 11 years of age were enrolled and received the two-dose mRNA COVID-19 vaccine (BNT162b2) regimen or the inactivated (CoronaVac) vaccine followed by the BNT162b2 vaccine regimen. In addition, healthy children who received two doses of BBIBP-CorV between 1 and 3 months prior were enrolled to receive a heterologous BNT162b2 as a third dose (booster). Reactogenicity was assessed by a self-reported online questionnaire. Immunogenicity analysis was performed to determine binding antibodies to wild-type SARS-CoV-2. Neutralizing antibodies to Omicron variants (BA.2 and BA.5) were tested using the focus reduction neutralization test. Overall, 166 eligible children were enrolled. Local and systemic adverse events which occurred within 7 days after vaccination were mild to moderate and well-tolerated. The two-dose BNT162b2, CoronaVac followed by BNT162b2, and two-dose BBIBP-CorV followed by BNT162b2 groups elicited similar levels of anti-receptor-binding domain (RBD) IgG. However, the two-dose BNT162b2 and two-dose BBIBP-CorV followed by BNT162b2 groups elicited higher neutralizing activities against the Omicron BA.2 and BA.5 variant than the CoronaVac followed by BNT162b2 group. The CoronaVac followed by BNT162b2 group elicited low neutralizing activities against the Omicron BA.2 and BA.5 variant. A third dose (booster) mRNA vaccine should be prioritized for this group., (© 2023 Wiley Periodicals LLC.)

Background: Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection can be asymptomatic in young children. Therefore, the true rate of infection is likely underestimated. Few data are available on the rate of infections in young children, and studies on SARS-CoV-2 seroprevalence among children during the omicron wave are limited. We assessed the SARS-CoV-2 infection-induced seroprevalence among children and estimated the associated risk factors for seropositivity., Methods: A longitudinal serological survey was conducted from January 2021 through December 2022. The inclusion criteria were healthy children between 5 and 7 years old and their parents or legal guardians provided written informed consent. Samples were tested for anti-nucleocapsid (N) IgG and anti-receptor binding domain (RBD) IgG using a chemiluminescent microparticle immunoassay (CMIA), and total anti-RBD immunoglobulin (Ig) was detected using an electrochemiluminescence immunoassay (ECLIA). The vaccination and SARS-CoV-2 infection history were collected., Results: In all, 457 serum samples were obtained from 241 annually followed-up children in this longitudinal serological survey. Of these, 201 participants provided samples at two serial time points-during the pre-omicron and omicron-dominant wave. Overall, seroprevalence induced by SARS-CoV-2 infection increased from 9.1% (22/241) during the pre-omicron to 48.8% (98/201) during the omicron wave. Amongst seropositive individuals, the infection-induced seropositivity was lower in vaccinated participants with two doses of BNT162b2 than in the unvaccinated participants (26.4% vs. 56%; OR, 0.28; 95%CI: 0.14-0.58). Nevertheless, the ratio of seropositive cases per recalled infection was 1.63 during the omicron dominant wave. The overall seroprevalence induced by infection, vaccination, and hybrid immunity was 77.1% (155/201) between January and December 2022., Conclusions: We report an increase in infection-induced seroprevalence among children during the omicron wave. These findings highlight that a seroprevalence survey can help determine the true rate of infection, particularly in asymptomatic infection, and optimize public health policies and vaccine strategies in the pediatric population., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Suntronwong et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The aim of this study is to investigate the reactogenicity and immunogenicity of the fourth dose using monovalent mRNA vaccines after different three-dose regimens and to compare the 30 µg BNT162b2 and 50 µg mRNA-1273 vaccines. This prospective cohort study was conducted between June and October 2022. The self-recorded reactogenicity was evaluated on the subsequent 7 days after a fourth dose. The binding and neutralizing activity of antibodies against the Omicron BA.4/5 variants were determined. Overall, 292 healthy adults were enrolled and received BNT162b2 or mRNA-1273. Reactogenicity was mild to moderate and well tolerated after a few days. Sixty-five individuals were excluded. Thus, 227 eligible individuals received a fourth booster dose of BNT162b2 ( n = 109) and mRNA-1273 ( n = 118). Most participants, regardless of the type of previous three-dose regimens, elicited a significantly high level of binding antibodies and neutralizing activity against Omicron BA.4/5 28 days after a fourth dose. The neutralizing activity against Omicron BA.4/5 between the BNT162b2 (82.8%) and mRNA-1273 (84.2%) groups was comparable with a median ratio of 1.02. This study found that the BNT162b2 and mRNA-1273 vaccines can be used as a fourth booster dose for individuals who were previously immunized with any prior three-dose mix-and-match COVID-19 vaccine regimens.

Objectives: To report the safety and immunogenicity profile of a protein subunit vaccine (Covovax TM ) given as a third (booster) dose to individuals primed with different primary vaccine regimens., Methods: A third dose was administered to individuals with an interval range of 3-10 months after the second dose. The four groups were classified according to their primary vaccine regimens, including two-dose BBIBP-CorV, AZD1222, BNT162b2, and CoronaVac/AZD1222. Immunogenicity analysis was performed to determine binding antibodies, neutralizing activity, and the T-cell responses., Results: Overall, 210 individuals were enrolled and boosted with the Covovax TM vaccine. The reactogenicity was mild to moderate. Most participants elicited a high level of binding and neutralizing antibody against Wild-type and Omicron variants after the booster dose. In participants who were antinucleocapsid immunoglobulin G-negative from all groups, a booster dose could elicit neutralizing activity to Wild-type and Omicron variants by more than 95% and 70% inhibition at 28 days, respectively. The Covovax TM vaccine could elicit a cell-mediated immune response., Conclusion: The protein subunit vaccine (Covovax TM ) can be proposed as a booster dose after two different priming dose regimens. It has strong immunogenicity and good safety profiles., Competing Interests: Declaration of competing interest The authors have no competing interests to declare., (Copyright © 2022 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Objectives: To investigate the seroprevalence of respiratory syncytial virus (RSV) infections in young children, the correlation between RSV antibody levels in maternal and cord serum, and to provide evidence of RSV reinfection in Thai children after primary infections., Methods: Serum samples were collected from 302 mothers and 291 children between 2015 and 2021. Maternal and cord blood were collected at birth. Serial serum samples of children were collected at the ages of 2, 7, 18, 19, 24, 36, 48, and 60 months and the presence of anti-RSV immunoglobulin G (IgG) was tested using an enzyme-linked immunosorbent assay., Results: The cord: maternal serum antibody ratio was 1.09 (95% confidence interval 1.08-1.11). Although >90% of babies at birth were seropositive through transplacental transfer, antibody levels gradually declined, with the highest seronegative rate (91.9%) at 7 months of age. Subsequently, anti-RSV IgG levels increased with age, most likely due to natural infection. One-third of the children showed evidence of reinfection as determined by seroconversion of anti-RSV IgG or increased titers of at least 50 relative units/ml., Conclusion: Waning of RSV antibodies in infants is rapid, and RSV infection subsequently increases anti-RSV IgG titers. RSV vaccination in children before the age of 7 months should be recommended., (Copyright © 2022 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: The use of an inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine (CoronaVac) against SARS-CoV-2 is implemented worldwide. However, waning immunity and breakthrough infections have been observed. Therefore, we hypothesized that the heterologous booster might improve the protection against the delta and omicron variants., Methods: A total of 224 individuals who completed the 2-dose CoronaVac for 6 months were included. We studied reactogenicity and immunogenicity after a heterologous booster with the inactivated vaccine (BBIBP), the viral vector vaccine (AZD1222), and the messenger ribonucleic acid (mRNA) vaccine (both BNT162B2 and mRNA-1273). We also determined immunogenicity at 3- and 6-month boosting intervals., Results: The solicited adverse events were mild to moderate and well tolerated. Total receptor binding domain (RBD) immunoglobulin (Ig), anti-RBD IgG, focus reduction neutralization test (FRNT50) against delta and omicron variants, and T-cell response were highest in the mRNA-1273 group followed by the BNT162b2, AZD1222, and BBIBP groups, respectively. We also witnessed a higher total Ig anti-RBD in the long-interval than in the short-interval group., Conclusions: All 4 booster vaccines significantly increased binding and neutralizing antibodies in individuals immunized with 2 doses of CoronaVac. The present evidence may benefit vaccine strategies to thwart variants of concern, including the omicron variant., Competing Interests: Potential conflicts of interest. All authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest., (© The Author(s) 2022. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

The coronavirus disease 2019 (COVID-19) pandemic has been a serious healthcare problem worldwide since December 2019. The third dose of heterologous vaccine was recently approved by World Health Organization. The present study compared the reactogenicity and immunogenicity of the reduced and standard third booster dose of the BNT162b2 and mRNA-1273 vaccine in adults who previously received the two-dose CoronaVac vaccine. Results showed that headache, joint pain, and diarrhea were more frequent in the 15 μg- than the 30 μg-BNT162b2 groups, whereas joint pain and chilling were more frequent in the 100 μg- than the 50 μg-mRNA-1273 groups. No significant differences in immunogenicity were detected. These findings demonstrate that the reduced dose of the mRNA vaccines elicited antibody responses against the SARS-CoV-2 delta and omicron variants that were comparable to the standard dose. The reduced dose could be used to increase vaccine coverage in situations of limited global vaccine supply., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [Sittisak Honsawek and Yong Poovorawan reports administrative support was provided by Chulalongkorn University Faculty of Medicine. Sitthichai Kanokudom reports financial support was provided by the Second Century Fund (C2F). Yong Poovorawan reports administrative support and equipment, drugs, or supplies were provided by the Center of Excellence in Clinical Virology, Chulalongkorn University, and King Chulalongkorn Memorial Hospital. Yong Poovorawan reports equipment, drugs, or supplies was provided by National Research Council of Thailand (NRCT). Yong Poovorawan reports equipment, drugs, or supplies was provided by Health Systems Research Institute (HSRI).]., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Objectives: The SARS-CoV-2 Omicron variant presents numerous mutations potentially able to evade neutralizing antibodies (NAbs) elicited by COVID-19 vaccines. Therefore, this study aimed to provide evidence on a heterologous booster strategy to overcome the waning immunity against Omicron variants., Methods: Participants who completed the Oxford/AstraZeneca (hereafter AZD1222) vaccine dose for 5-7 months were enrolled. The reactogenicity and persistence of immunogenicity in both humoral and cellular response after a homologous or heterologous booster with the AZD1222 and messenger RNA (mRNA) vaccines (BNT162b2, full, or half-dose mRNA-1273) administered 6 months after primary vaccination were determined., Results: A total of 229 individuals enrolled, and waning of immunity was observed 5-7 months after the AZD1222-primed vaccinations. Total receptor-binding domain (RBD) immunoglobulin (Ig) levels, anti-RBD IgG, and focus reduction neutralization test against Omicron BA.1 and BA.2 variants and T cell response peaked at 14-28 days after booster vaccination. Both the full and half dose of mRNA-1273 induced the highest response, followed by BNT162b2 and AZD1222. At 90 days, the persistence of immunogenicity was observed among all mRNA-boosted individuals. Adverse events were acceptable for all vaccines., Conclusion: A heterologous mRNA booster provided a significantly superior boost of binding and NAbs levels against the Omicron variant compared with a homologous booster in individuals with AZD1222-primed vaccinations., Competing Interests: Declaration of Competing Interest The authors have no competing interests to declare., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Coronavirus disease 2019 (COVID-19) booster vaccination is being comprehensively evaluated globally due to waning immunity and the emergence of new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. Therefore, this study aimed to evaluate antibody responses in individuals vaccinated with two doses of the BBIBP-CorV vaccine and to explore the boosting effect of the different vaccine platforms in BBIBP-CorV-primed healthy adults, including a viral vector vaccine (AZD122) and mRNA vaccines (BNT162b2 and mRNA-1273). The results showed that in the BBIBP-CorV prime group, the total receptor-binding domain (RBD) immunoglobulin (Ig) and anti-RBD IgG levels waned significantly at three months after receiving the second dose. However, after the booster, RBD-specific binding antibody levels increased. Neutralizing antibody measured by a surrogate neutralization test showed inhibition over 90% against the SARS-CoV-2 delta variant but less than 70% against the omicron variant after the third dose on day 28. All booster vaccines could induce the total IFN-ɣ T-cell response. The reactogenicity was acceptable and well-tolerated without serious adverse events. This study supports the administration of the third dose with either a viral vector or mRNA vaccine for BBIBP-CorV-primed individuals to stimulate antibody and T-cell responses.

Limited data are available on the responses to heterologous vaccine regimens for SARS-CoV-2, especially among countries using inactivated and adenoviral-vectored vaccines. A total of 77 participants who received heterologous inactivated COVID-19 vaccine (CoronaVac) and adenoviral-vectored vaccine (AZD1222) were enrolled in our study. There were two comparison groups vaccinated with the homologous CoronaVac (N = 79) and AZD1222 (N = 78) regimen. All sera samples were tested for anti-receptor-binding-domain IgG (anti-RBD IgG) using a chemiluminescent microparticle immunoassay (CMIA). The neutralizing activity in a subset of serum samples was tested against the original Wuhan strain and variants of concern, B.1.1.7, B.1.617.2 and B.1.351, using an enzyme-linked immunosorbent assay (ELISA)-based surrogate virus neutralization test (sVNT). The heterologous CoronaVac/AZD1222 vaccine induced higher levels of anti-RBD IgG than that of two-dose homologous CoronaVac or AZD1222 vaccines (p < 0.001). Sera samples of the CoronaVac/AZD1222 vaccine recipients elicited higher neutralizing antibody activity against the original Wuhan and all variants of concern than in the recipients of the two-dose CoronaVac. The heterologous CoronaVac followed by AZD1222 is an alternative regimen to combat with the SARS-CoV-2 variants in case of vaccine shortage with improved immunogenicity compared to the homologous CoronaVac regimen., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants and the waning of immunity in vaccinated individuals is resulting in increased numbers of SARS-CoV-2 breakthrough infections. This study investigated binding antibody responses and neutralizing activities against SARS-CoV-2 variants, in patients with COVID-19 who had been fully vaccinated with CoronaVac ( n = 77), individuals who had been fully vaccinated with CoronaVac but had not contracted COVID-19 ( n = 170), and individuals who had received AZD1222 as a third vaccination ( n = 210). Breakthrough infection was generally detected approximately 88 days after the second CoronaVac vaccination (interquartile range 68-100 days). Blood samples were collected at a median of 34 days after infection. Binding antibody levels in sera from patients with breakthrough infection were significantly higher than those in individuals who had received AZD1222 as a third vaccination. However, neutralizing activities against wild-type and variants, including alpha (B.1.1.7), beta (B.1.351), and delta (B.1.617.2), were comparable in patients with breakthrough infections and individuals who received a third vaccination with AZD1222, which exceeds 90%. Omicron (B.1.1.529) was neutralized less effectively by serum from breakthrough infection patients, with a 6.3-fold reduction compared to delta variants. The study suggests that breakthrough infection after two doses of an inactivated vaccine can induce neutralizing antibodies against omicron. Further investigation is needed to assess the long-term persistence of antibodies against the omicron variant.

In June 2021, Thailand was hit by the delta variant of SARS-CoV-2 resulting in the biggest wave of COVID-19. Due to the widespread delta variant, more than 600 healthcare workers had COVID-19 despite completion of two-dose CoronaVac. The Ministry of Public Health recommended that healthcare workers received a third dose of AZD1222 to increase level of protection against SARS-CoV-2. However, immune response after the AZD1222 booster in individuals who completed the two-dose CoronaVac vaccine are limited. In this study, sera from those who received a booster of AZD1222 in June-July 2021 were tested for SARS-CoV-2 spike receptor-binding-domain (RBD) IgG, anti-RBD total immunoglobulins and anti-spike protein 1 (S1) IgA. The neutralizing activities in a subset of serum samples were tested against the wild type and variants of concern (B.1.1.7, B.1.617.2, and B.1.351) using an enzyme-linked immunosorbent assay-based surrogate virus neutralization test. Participants who received the booster of AZD1222 possessed higher levels of spike RBD-specific IgG, total immunoglobulins, and anti-S1 IgA than the two-dose vaccinees (p < 0.001). They also elicited higher neutralizing activity against the wild type and all variants of concern than the recipients of the two-dose vaccines. This study demonstrated a high immunogenicity of the AZD1222 booster in individuals who completed the two-dose inactivated vaccines., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The coronavirus disease 2019 (COVID-19) pandemic has become a severe healthcare problem worldwide since the first outbreak in late December 2019. Currently, the COVID-19 vaccine has been used in many countries, but it is still unable to control the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, despite patients receiving full vaccination doses. Therefore, we aimed to appraise the booster effect of the different platforms of vaccines, including inactivated vaccine (BBIBP), viral vector vaccine (AZD122), and mRNA vaccine (BNT162b2), in healthy adults who received the full dose of inactivated vaccine (CoronaVac). The booster dose was safe with no serious adverse events. Moreover, the immunogenicity indicated that the booster dose with viral vector and mRNA vaccine achieved a significant proportion of Ig anti-receptor binding domain (RBD), IgG anti-RBD, and IgA anti-S1 booster response. In contrast, inactivated vaccine achieved a lower booster response than others. Consequently, the neutralization activity of vaccinated serum had a high inhibition of over 90% against SARS-CoV-2 wild-type and their variants (B.1.1.7-alpha, B.1.351-beta, and B.1.617.2-delta). In addition, IgG anti-nucleocapsid was observed only among the group that received the BBIBP booster. Our study found a significant increase in levels of IFN-ɣ secreting T-cell response after the additional viral vector or mRNA booster vaccination. This study showed that administration with either viral vector (AZD1222) or mRNA (BNT162b2) boosters in individuals with a history of two doses of inactivated vaccine (CoronaVac) obtained great immunogenicity with acceptable adverse events.

Assessing the seroprevalence of the high-risk individuals against the influenza virus is essential to evaluate the progress of vaccine implementation programs and establish influenza virus interventions. Herein, we identified the pre-existing cross-protection of the circulating seasonal influenza viruses among the older-aged population. A cross-sectional study was performed base on the 176 residual sera samples collected from older adults aged 60 to 95 years without a history of vaccination in rural Thailand in 2015. Sera antibody titers against influenza A and B viruses circulating between 2016 and 2019 were determined by hemagglutination inhibition assay. These findings indicated the low titers of pre-existing antibodies to circulating influenza subtypes and showed age-independent antibody titers among the old adults. Moderate seropositive rates (HAI ≥ 1:40) were observed in influenza A viruses (65.9%A(H3N2), 50.0% for A(H1N1) pdm09), and found comparatively lower rates in influenza B viruses (14% B/Yam2, 21% B/Yam3 and 25% B/Vic). Only 5% of individuals possessed broadly protective antibodies against both seasonal influenza A and B virus in this region. Our findings highlighted the low pre-existing antibodies to circulating influenza strains in the following season observed in older adults. The serological study will help inform policy-makers for health care planning and guide control measures concerning vaccination programs., Competing Interests: The authors have declared that no competing interests exist.

We monitored the circulating strains and genetic variation among seasonal influenza A and B viruses in Thailand between July 2017 and March 2020. The hemagglutinin gene was amplified and sequenced. We identified amino acid (AA) changes and computed antigenic relatedness using the P epitope model. Phylogenetic analyses revealed multiple clades/subclades of influenza A(H1N1)pdm09 and A(H3N2) were circulating simultaneously and evolved away from their vaccine strain, but not the influenza B virus. The predominant circulating strains of A(H1N1)pdm09 belonged to 6B.1A1 (2017-2018) and 6B.1A5 (2019-2020) with additional AA substitutions. Clade 3C.2a1b and 3C.2a2 viruses co-circulated in A(H3N2) and clade 3C.3a virus was found in 2020. The B/Victoria-like lineage predominated since 2019 with an additional three AA deletions. Antigenic drift was dominantly facilitated at epitopes Sa and Sb of A(H1N1)pdm09, epitopes A, B, D and E of A(H3N2), and the 120 loop and 190 helix of influenza B virus. Moderate computed antigenic relatedness was observed in A(H1N1)pdm09. The computed antigenic relatedness of A(H3N2) indicated a significant decline in 2019 (9.17%) and 2020 (- 18.94%) whereas the circulating influenza B virus was antigenically similar (94.81%) with its vaccine strain. Our findings offer insights into the genetic divergence from vaccine strains, which could aid vaccine updating.

Yearly increase in influenza activity is associated with cold and dry winter in the temperate regions, while influenza patterns in tropical countries vary significantly by regional climates and geographic locations. To examine the association between influenza activity in Thailand and local climate factors including temperature, relative humidity, and rainfall, we analyzed the influenza surveillance data from January 2010 to December 2018 obtained from a large private hospital in Bangkok. We found that approximately one in five influenza-like illness samples (21.6% or 6,678/30,852) tested positive for influenza virus. Influenza virus typing showed that 34.2% were influenza A(H1N1)pdm09, 46.0% were influenza A(H3N2), and 19.8% were influenza B virus. There were two seasonal waves of increased influenza activity. Peak influenza A(H1N1)pdm09 activity occurred in February and again in August, while influenza A(H3N2) and influenza B viruses were primarily detected in August and September. Time series analysis suggests that increased relative humidity was significantly associated with increased influenza activity in Bangkok. Months with peak influenza activity generally followed the most humid months of the year. We performed the seasonal autoregressive integrated moving average (SARIMA) multivariate analysis of all influenza activity on the 2011 to 2017 data to predict the influenza activity for 2018. The resulting model closely resembled the actual observed overall influenza detected that year. Consequently, the ability to predict seasonal pattern of influenza in a large tropical city such as Bangkok may enable better public health planning and underscores the importance of annual influenza vaccination prior to the rainy season., Competing Interests: The authors have declared that no competing interests exist.

Rotavirus infection is the most common cause of viral diarrhea in infants and young children but uncommon and usually asymptomatic in adults. In the winter of 2017-2018, a large-scale outbreak of rotavirus in both children and adults was reported in Thailand. The current study focused on the prevalence, genotyping, and molecular characterization of rotavirus infections in Thai adults from July 2016 to December 2019. In 2,598 stool samples collected from adult residents of Bangkok (aged #x2265; 15 years) with acute gastroenteritis, rotavirus was detected via real-time RT-PCR analysis of the VP6 gene. G, P and I genotypes were determined by direct sequencing of VP7, VP4, and VP6 genes, respectively. Our results showed 8.7% (226/2,598) of stool samples were positive for rotavirus. The incidence of rotavirus was high during the winter season of 2017-2018 (17.7%) compared to another studied periods (4.5% between July 2016- October 2017 and 2.8% between March 2018- December 2019). Nucleotide sequencing of VP7 and VP4 revealed G3P[8] as the predominant strain (33.2%,75/226), followed by G9P[8] (17.3%,39/226), and G2P[4] (15.0%,34/226). Uncommon G and P combinations were additionally detected at low frequencies. VP6 sequencing was conducted to discriminate I genotype between the Wa and DS-1 genogroup. The unusual DS-1-like G3P[8] strain was most prevalent amomg rotavirus strains detected in this study (29.6%, 67/226), and the corresponding VP7 sequences showed high nucleotide identity with unusual DS-1-like globally circulating strains. Our study demonstrates that rotavirus outbreaks in adults are attributable not only to high prevalence of RV infection but also the unusual DS-like genogroup. The collective findings reinforce the importance of investigating rotavirus diagnosis in adults suffering from acute gastroenteritis and taking appropriate preventive measures., Competing Interests: The authors have declared that no competing interests exist.

Background: Hepatitis E virus (HEV) infection in several industrialized and developing countries is associated with the consumption of pork and other meat products, an exposure risk among the majority of blood donors. We aimed to evaluate the prevalence of HEV in plasma from healthy blood donors in Thailand., Study Design and Methods: We screened blood samples collected between October and December 2015, from 30,115 individual blood donors in 5020 pools of six, for HEV RNA using in-house real-time reverse-transcription polymerase chain reaction (RT-PCR). Thrice-reactive samples were subjected to a commercial real-time RT-PCR (cobas HEV test) and evaluated for anti-HEV immunoglobulin M and immunoglobulin G antibodies. Genotyping using nested RT-PCR, nucleotide sequencing, and phylogenetic analysis was performed., Results: Twenty-six donors were positive for HEV RNA by the in-house assay, nine of whom were also positive by cobas test. None of the latter were reactive for anti-HEV immunoglobulin M or immunoglobulin G antibodies. Six samples were successfully genotyped and found to be HEV genotype 3. Thus, the frequency of HEV infection among healthy Thai blood donors is 1 in 1158., Conclusion: The presence of HEV RNA in the Thai blood supply was comparable to the rates reported in western European countries, but higher than in North America and Australia., (© 2018 AABB.)

The World Health Organization aims to eliminate HCV infection worldwide by 2030. A targeted HCV screening policy is currently unavailable in Thailand, but a decrease in HCV infection has been observed in the country. However, a previous study showed that there was a higher HCV seroprevalence in adults aged between 30-64 years in the Phetchabun province (15.5%), as compared to the Khon Kaen province (3.6%). It was hypothesized that young adults had a lower rate of HCV seropositivity; this was determined by the age distribution of anti-HCV in Phetchabun and with the identification of high seroprevalence birth cohorts. In order to compare the provincial findings to the national level, anti-HCV birth cohorts were further analyzed in Khon Kaen (averaged-HCV prevalence) as well as the Thai data set that was derived from the previous literature. Thai individuals aged between 18-30 years residing in Phetchabun (n = 1453) were recruited, tested for the presence of anti-HCV antibodies and viral RNA and completed questionnaires that were designed to identify HCV exposure risks. Data was collected and compiled from previously published articles (n = 1667, age 30-64 years). The HCV seropositivity in Phetchabun by age group (18-64, at 5-year intervals) and the birth year were tabulated parallel to the Khon Kaen data set (n = 2233) in conjunction with data from the national survey 2014 (n = 5964) representing the Thai population. Factors such as age, male gender, agricultural work, blood transfusion, intravenous drug use and having a tattoo were associated with anti-HCV positivity in Phetchabun. HCV seroprevalence was less than 4.0% (ranging from 0.0-3.5%) from the age of 18-34 years. A dramatic increase of 15.1% was found in adults aged greater than or equal to 35 years, whereas, the age group in Khon Kaen and the national population with increasing prevalence of HCV were older (≥40). The HCV seropositivity cohort accumulated for those born between 1951-1982 accounted for 71.4-100.0% of all seropositive individuals. Subsequently, new cases occurred sporadically. This finding provides evidence that there is a disproportionately high HCV seroprevalence among people born before 1983 (or aged ≥35). This cohort should be targeted for priority screening as part of the national HCV screening policy. Incorporating this birth cohort with other risk factors could improve HCV diagnostic rates, resulting in overall improvements in parallel to those given by novel antiviral treatment., Competing Interests: The authors have declared that no competing interests exist.

The prevalence of hepatitis C virus (HCV) infection has been decreasing globally, but the growing effects of HCV-related morbidity and mortality remain of concern. Advances in curative medicine, involving direct-acting antivirals (DAAs), have led many countries to aim to eradicate HCV. Information on epidemiology and disease burden is essential for national policy development. Thus, this study aimed to determine the HCV-related hepatic disease burden in areas of Thailand with high and average HCV prevalence in order to extrapolate the viral burden across Thailand. Patients previously diagnosed as positive for anti-HCV antibodies were recruited to assess chronic HCV infection (CHC) status, liver function, HCV-RNA level and hepatic fibrosis. The number of patients eligible for Universal Health Coverage (UC) scheme and the approximately required expenditure on interferon (IFN)-based treatment were estimated. In areas of both high (12%) and average (2%) HCV viremic prevalence, over half of the patients (52.2% to 62.5%) had advanced liver fibrosis (F3 and F4). A striking percentage of patients with F4 (38.9%) were found in the high-prevalence area, while comparable proportions of advanced liver fibrosis presented in the two areas and disease burden peaked at 50-59 years. Under the current UC program treatment scenario, 78-83% of CHC patients with stage F2-F4 fibrosis were eligible for treatment. The estimated expenditure required for overall CHC treatment across the whole country was 1,240 million USD at this current status, but the declining cost of generic DAA-based therapy may reduce the requirement to <90 million USD. This study provides information on the estimated number of CHC patients, liver disease burden and expenditure requirements for Thailand. To eliminate HCV by 2030, proactive government strategies raising public health to minimize transmission and emphasizing targeted screen-and-treatment programs, novel therapeutic guideline development for decentralizing treatment, and effective budget allocation are urgently needed.

Influenza virus evolves rapidly due to the accumulated genetic variations on the viral sequence. Unlike in North America and Europe, influenza season in the tropical Southeast Asia spans both the rainy and cool seasons. Thus, influenza epidemiology and viral evolution sometimes differ from other regions, which affect the ever-changing efficacy of the vaccine. To monitor the current circulating influenza viruses in this region, we determined the predominant influenza virus strains circulating in Thailand between January 2016 and June 2017 by screening 7,228 samples from patients with influenza-like illness. During this time, influenza A(H3N2) virus was the predominant influenza virus detected. We then phylogenetically compared the hemagglutinin (HA) gene from a subset of these A(H3N2) strains (n = 62) to the reference sequences and evaluated amino acid changes in the dominant antigenic epitopes on the HA protein structure. The divergence of the circulating A(H3N2) from the A/Hong Kong/4801/2014 vaccine strain formed five genetic groups (designated I to V) within the 3C.2a clade. Our results suggest a marked drift of the current circulating A(H3N2) strains in Thailand, which collectively contributed to the declining predicted vaccine effectiveness (VE) from 74% in 2016 down to 48% in 2017.

The core antigen of the hepatitis C virus (HCV Ag) presents an alternative marker to HCV RNA when screening patients for HCV viremia. This study sought to evaluate the utility of HCV Ag as a marker to assess active HCV infection in individuals residing in an HCV-endemic area. From 298 HCV-seropositive individuals evaluated for the presence of anti-HCV antibody, HCV Ag and HCV RNA, anti-HCV antibody was detected in 252 individuals (signal-to-cutoff ratios ≥5), HCV RNA was detected in 222 individuals (88%), and HCV Ag was reactive (≥3 fmol/L) in 220 individuals (87%). HCV genotype 1, 3, and 6 were identified. HCV Ag significantly correlated with HCV RNA irrespective of HCV genotype and/or HBV co-infection (log HCV RNA = 2.67 + 0.95 [log HCV Ag], R 2  = 0.890, p  < 0.001). To predict HCV viremia (HCV Ag ≥ 3 fmol/L), the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were 99%, 99%, 100%, 100% and 97%, respectively. We concluded that HCV Ag was a good surrogate marker for HCV RNA and could be used to diagnose active HCV infection in a resource-limited setting. As a result, a cost-effective strategy for screening and identifying active HCV carriers using HCV Ag detection would enable more patients access to efficacious and increasingly affordable direct-acting antivirals (DAAs) for the treatment of HCV infection., Competing Interests: The authors declare there are no competing interests.

Non-bacterial acute gastroenteritis (AGE) associated with virus infection affects individuals living in developing countries, especially children. To investigate whether shedding of certain human enterovirus (EV) is more frequently detected in the stool of individuals with AGE of unknown etiology than individuals without AGE symptoms, we tested fecal samples collected from 2,692 individuals with diarrhea between January 2010 and December 2016. Samples were tested for rotavirus, norovirus, and EV by reverse-transcription polymerase chain reaction (RT-PCR) and adenovirus by PCR. EV-positive samples were subjected to sequencing and phylogenetic analysis to identify EV species and types. Findings were compared to EV found in 1,310 fecal samples from individuals without AGE who were diagnosed with hand, foot, and mouth disease (HFMD). While the majority of viruses identified in AGE consisted of human rotavirus (22.7%), norovirus (11.4%) and adenovirus (9.3%), we identified EV (6.2%) belonging mainly to species B, C, and rhinovirus. In contrast, >92% of EV found without AGE symptoms belonged to species A. Although AGE symptoms are not often attributed to EV infection, EV was associated with diarrhea of unknown etiology at least in 3.4% of AGE cases. While CV-A6 was most likely to be found in stools of HFMD patients, rhinovirus A and C were the two most common EV species associated with AGE. Elucidating group-specific EV infection in diseases with and without AGE will be useful in assisting identification, clinical management, and the surveillance of EV infection in the community.

Improved awareness of the hepatitis C virus (HCV) transmission has contributed to the overall decline in the HCV infection rate in some developing countries including Thailand. Chronic HCV infection in some rural Thai communities, however, presents a challenge in the efforts to treat and manage HCV-related diseases. Published and unpublished studies have suggested an unusually high incidence of HCV infection in a Thai province of Phetchabun compared to elsewhere in Thailand. To determine the magnitude of HCV infection and identify potential factors contributing to the higher rate of HCV infection in this province, we performed a population-based study in Phetchabun (n = 1667) and the neighboring Khon Kaen province (n = 1410) where HCV prevalence is much lower. Individuals between 30 and 64 years old completed detailed questionnaires designed to identify HCV risk factors and provided blood samples for anti-HCV antibody screening. The anti-HCV seropositive rates were 15.5% (259/1667) in Phetchabun and 3.6% (51/1410) in Khon Kaen. Positive samples were subsequently genotyped for HCV core gene sequence and assessed for the hepatitis B virus surface antigen (HBsAg) and human immunodeficiency virus antigen/antibody (HIV Ag/Ab). More individuals in Phetchabun possessed the combined presence of HBsAg (5.0%) and HIV Ag/Ab (0.4%) than those in Khon Kaen (3.9% HBsAg and 0.0% HIV Ag/Ab). While male gender, intravenous drug use (IVDU) and tattoos were significant HCV risk factors in both provinces (p <0.05), education less than high school and agriculture-related occupation were additionally associated with HCV in Phetchabun. HCV genotypes 6, 3, and 1 were identified in similar frequency in both provinces. We estimated that prevalence of HCV seropositivity and viremic carriers were higher in Phetchabun (143 and 111 per 1000) than in Khon Kaen (34 and 22 per 1000). Finally, we derived a simple risk factor-based scoring system as a useful preclinical tool to screen individuals at risk of chronic HCV infection prior to intervention. Knowledge gained from this study will assist in HCV screening and promote access to anti-viral treatment in high-risk groups.

The neuraminidase inhibitors (NAIs) oseltamivir and zanamivir are commonly used for the treatment and control of influenza A and B virus infection. However, the emergence of new influenza virus strains with reduced susceptibility to NAIs may appear with the use of these antivirals or even naturally. We therefore screened the neuraminidase (NA) sequences of seasonal influenza virus A(H1N1), A(H1N1)pdm09, A(H3N2), and influenza B virus strains identified in Thailand for the presence of substitutions previously reported to reduce susceptibility to NAIs. We initially examined oseltamivir resistance (characterized by the H275Y mutation in the NA gene) in 485 A(H1N1)pdm09 strains circulating in Thailand and found that 0.82% (4/485) had this substitution. To further evaluate the evolution of the NA gene, we also randomly selected 98 A(H1N1)pdm09, 158 A(H3N2), and 69 influenza B virus strains for NA gene amplification and sequencing, which revealed various amino acid mutations in the active site of the NA protein previously shown to be associated with reduced susceptibility to NAIs. Phylogenetic analysis of the influenza virus strains from this study and elsewhere around the world, together with the estimations of nucleotide substitution rates and selection pressure, and the predictions of B-cell epitopes and N-linked glycosylation sites all provided evidence for the ongoing evolution of NA. The overall rates of NA evolution for influenza A viruses were higher than for influenza B virus at the nucleotide level, although influenza B virus possessed more genealogical diversity than that of influenza A viruses. The continual surveillance of the antigenic changes associated with the NA protein will not only contribute to the influenza virus database but may also provide a better understanding of selection pressure exerted by antiviral use.

Swine is an economically important livestock, yet pork consumption and close contact with pigs are associated with the risk of hepatitis E virus (HEV) infection. Limited data on the prevalence of HEV in Southeast Asia have mainly examined farm animals. To investigate the potential zoonotic transmission of HEV from dietary consumption of pork and variety meats (i.e., offal or organ meats), we obtained 1090 liver, 559 pork meat, and 556 intestine samples from fresh markets in the Bangkok metropolitan area between November 2014 and February 2015. The presence of HEV was assessed using reverse-transcription polymerase chain reaction. Concurrently, 720 bile and 553 fecal samples from a slaughterhouse were also examined. Overall, HEV RNA was found in 0.23 % of the market samples and 3.93 % of the slaughterhouse samples. Fecal and bile samples were more likely to test positive compared to liver, pork, and intestine samples (p < 0.001). Phylogenetic analysis showed that all HEV sequences obtained in this study formed a cluster closely related to genotype 3f. Pork and variety meats derived from pigs are commonly sold in fresh markets throughout Southeast Asia. Here, a relatively low HEV prevalence from pork and variety meats sold in Bangkok was found. Additional studies will be required to further assess potential dietary transmission of HEV elsewhere in the region.

Influenza B viruses comprise two lineages, Victoria (B/Vic) and Yamagata (B/Yam), which co-circulate globally. The surveillance data on influenza B virus lineages in many countries often underestimate the true prevalence due to the lack of a rapid, accurate, and cost-effective method for virus detection. We have developed a real-time PCR with melting curve analysis for lineage-specific differential detection of influenza B virus. By amplifying a region of the hemagglutinin gene using real-time PCR with SYBR Green I dye, B/Vic and B/Yam could be differentiated based on their melting temperature peaks. This method was efficient (B/Vic = 93.2 %; B/Yam 97.7 %), sensitive (B/Vic, 94.6 %; B/Yam, 96.3 %), and specific (B/Vic, 97.7 %; B/Yam, 97.1 %). The lower detection limit was 10(2) copies per microliter. The assay was evaluated using 756 respiratory specimens that were positive for influenza B virus, obtained between 2010 and 2015. The incidence of influenza B virus was approximately 18.9 % of all influenza cases, and the percentage was highest among children aged 6-17 years (7.57 %). The overall percentage of mismatched influenza B vaccine was 21.1 %. Our findings suggest that real-time PCR with melting curve analysis can provide a rapid, simple, and sensitive lineage-specific influenza B virus screening method to facilitate influenza surveillance.

Hepatitis B vaccination for newborns was introduced in two provinces in 1988 as part of Thailand's Expanded Program on Immunization (EPI), and extended to the whole country in 1992. Our previous studies showed that children and adolescents who were born after the implementation of this program had a carrier rate of less than 1%, compared with 5-6% before implementation. In 2014 we performed hepatitis B serosurveys among 5964 subjects in the different geographic regions of the country to evaluate the long-term immunogenicity and impact of universal hepatitis B vaccination in newborns as part of the 22-year EPI program, by assessing HBsAg, anti-HBc and anti-HBs seropositivity status. The number of HB virus (HBV) carriers, both children and young adults, who were born after universal HB vaccination was markedly reduced. The carrier rates among the age groups 6 months to 5 years, 5-10, 11-20, 21-30, 31-40, 41-50 and >50 years were respectively 0.1, 0.29, 0.69, 3.12, 3.78, 4.67 and 5.99%. The seropositivity rate for HBsAg in the post-EPI group was 0.6%, whereas in the pre-EPI group it was as high as 4.5% (p<0.001). HBV infection by means of detectable anti-HBc had also drastically declined in the population born after the HB vaccine was integrated into the EPI program. We estimated that the total number of HBV carriers amounted to 2.22 million, or 3.48% of the total population, most of whom are adults. The HB vaccine is the first vaccine shown to be effective in preventing the occurrence of chronic liver disease and hepatocellular carcinoma. Universal vaccination campaign will contribute to the eventual eradication of HBV-associated disease.

Hepatitis C virus (HCV) infection affects ≥ 180 million individuals worldwide especially those living in developing countries. Recent advances in direct-acting therapeutics promise effective treatments for chronic HCV carriers, but only if the affected individuals are identified. Good treatment coverage therefore requires accurate epidemiological data on HCV infection. In 2014, we determined the current prevalence of HCV in Thailand to assess whether over the past decade the significant number of chronic carriers had changed. In total, 5964 serum samples from Thai residents between 6 months and 71 years of age were obtained from 7 provinces representing all 4 geographical regions of Thailand and screened for the anti-HCV antibody. Positive samples were further analyzed using RT-PCR, sequencing, and phylogenetic analysis to identify the prevailing HCV genotypes. We found that 56 (0.94%) samples tested positive for anti-HCV antibody (mean age = 36.6±17.6 years), while HCV RNA of the core and NS5B subgenomic regions was detected in 23 (41%) and 19 (34%) of the samples, respectively. The seropositive rates appeared to increase with age and peaked in individuals 41-50 years old. These results suggested that approximately 759,000 individuals are currently anti-HCV-positive and that 357,000 individuals have viremic HCV infection. These numbers represent a significant decline in the prevalence of HCV infection. Interestingly, the frequency of genotype 6 variants increased from 8.9% to 34.8%, while the prevalence of genotype 1b declined from 27% to 13%. These most recent comprehensive estimates of HCV burden in Thailand are valuable towards evidence-based treatment coverage for specific population groups, appropriate allocation of resources, and improvement in the national public health policy.

Under selective pressure from the host immune system, antigenic epitopes of influenza virus hemagglutinin (HA) have continually evolved to escape antibody recognition, termed antigenic drift. We analyzed the genomes of influenza A(H3N2) and A(H1N1)pdm09 virus strains circulating in Thailand between 2010 and 2014 and assessed how well the yearly vaccine strains recommended for the southern hemisphere matched them. We amplified and sequenced the HA gene of 120 A(H3N2) and 81 A(H1N1)pdm09 influenza virus samples obtained from respiratory specimens and calculated the perfect-match vaccine efficacy using the pepitope model, which quantitated the antigenic drift in the dominant epitope of HA. Phylogenetic analysis of the A(H3N2) HA1 genes classified most strains into genetic clades 1, 3A, 3B, and 3C. The A(H3N2) strains from the 2013 and 2014 seasons showed very low to moderate vaccine efficacy and demonstrated antigenic drift from epitopes C and A to epitope B. Meanwhile, most A(H1N1)pdm09 strains from the 2012-2014 seasons belonged to genetic clades 6A, 6B, and 6C and displayed the dominant epitope mutations at epitopes B and E. Finally, the vaccine efficacy for A(H1N1)pdm09 (79.6-93.4%) was generally higher than that of A(H3N2). These findings further confirmed the accelerating antigenic drift of the circulating influenza A(H3N2) in recent years.