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Abstract The objective of this article is to draw lessons from the Thai experience in estimating vaccine effectiveness (VE) for coronavirus disease 2019 (COVID-19) based on routine service data. We found that a matched case–control design, using probability-based controls representing the varying vaccine coverage across the population over time, yielded a valid result for VE assessment. The proposed design has an advantage in its applicability drawing from the routine data monitoring system. Future studies that exercise other designs, such as test-negative and cohort studies, are recommended in order to compare and contrast the findings across different designs. To implement a continuous monitoring system on VE, the integration of data from different sources is needed. This requires long-term investment in the data monitoring system for the entire healthcare system.

Due to the widespread Omicron variant of SARS-CoV-2 in Thailand, the effectiveness of COVID-19 vaccines has become a major issue. The primary objective of this study is to examine the real-world effectiveness of COVID-19 vaccines based on secondary data acquired under normal circumstances in a real-world setting, to protect against treatment with invasive ventilation of pneumonia during January to April 2022, a period when Omicron was predominant. We conducted a nationwide test-negative case–control study. The case and control were matched with a ratio of 1:4 in terms of age, date of specimen collection, and hospital collection specimen and the odds ratio was calculated using conditional logistic regression. Overall, there was neither a distinction between mix-and-match regimens and homologous mRNA regimens against severe symptoms, nor was there a decline of the protective effect over the study period. The third and fourth dose boosters with ChAdOx1 nCoV-19 or mRNA vaccines provided high levels of protection against severe outcomes, approximately 87% to 100%, whereas two doses provided a moderate degree (70%). Thus, this study concludes that current national vaccine strategies provide favourable protective benefits against the Omicron variant. All Thais should receive at least two doses, while high-risk or vulnerable groups should be administered at least three doses.

The objective of this study is to explore the real-world effectiveness of various vaccine regimens to tackle the epidemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant in Thailand during September–December 2021. We applied a test-negative case control study, using nationwide records of people tested for SARS-CoV-2. Each case was matched with two controls with respect to age, detection date, and specimen collection site. A conditional logistic regression was performed. Results were presented in the form vaccine effectiveness (VE) and 95% confidence interval. A total of 1,460,458 observations were analyzed. Overall, the two-dose heterologous prime-boost, ChAdOx1 + BNT162b2 and CoronaVac + BNT162b2, manifested the largest protection level (79.9% (74.0–84.5%) and 74.7% (62.8–82.8%)) and remained stable over the whole study course. The three-dose schedules (CoronaVac + CoronaVac + ChAdOx1, and CoronaVac + CoronaVac + BNT162b2) expressed very high degree of VE estimate (above 80.0% at any time interval). Concerning severe infection, almost all regimens displayed very high VE estimate. For the two-dose schedules, heterologous prime-boost regimens seemed to have slightly better protection for severe infection relative to homologous regimens. Campaigns to expedite the rollout of third-dose booster shot should be carried out. Heterologous prime-boost regimens should be considered as an option to enhance protection for the entire population.

The emergence and rapid spread of novel DS-1-like G1P[8] human rotaviruses in Japan were recently reported. More recently, such intergenogroup reassortant strains were identified in Thailand, implying the ongoing spread of unusual rotavirus strains in Asia. During rotavirus surveillance in Thailand, three DS-1-like intergenogroup reassortant strains having G3P[8] (RVA/Human-wt/THA/SKT-281/2013/G3P[8] and RVA/Human-wt/THA/SKT-289/2013/G3P[8]) and G2P[8] (RVA/Human-wt/THA/LS-04/2013/G2P[8]) genotypes were identified in fecal samples from hospitalized children with acute gastroenteritis. In this study, we sequenced and characterized the complete genomes of strains SKT-281, SKT-289, and LS-04. On whole genomic analysis, all three strains exhibited unique genotype constellations including both genogroup 1 and 2 genes: G3-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2 for strains SKT-281 and SKT-289, and G2-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2 for strain LS-04. Except for the G genotype, the unique genotype constellation of the three strains (P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2) is commonly shared with DS-1-like G1P[8] strains. On phylogenetic analysis, nine of the 11 genes of strains SKT-281 and SKT-289 (VP4, VP6, VP1-3, NSP1-3, and NSP5) appeared to have originated from DS-1-like G1P[8] strains, while the remaining VP7 and NSP4 genes appeared to be of equine and bovine origin, respectively. Thus, strains SKT-281 and SKT-289 appeared to be reassortant strains as to DS-1-like G1P[8], animal-derived human, and/or animal rotaviruses. On the other hand, seven of the 11 genes of strain LS-04 (VP7, VP6, VP1, VP3, and NSP3-5) appeared to have originated from locally circulating DS-1-like G2P[4] human rotaviruses, while three genes (VP4, VP2, and NSP1) were assumed to be derived from DS-1-like G1P[8] strains. Notably, the remaining NSP2 gene of strain LS-04 appeared to be of bovine origin. Thus, strain LS-04 was assumed to be a multiple reassortment strain as to DS-1-like G1P[8], locally circulating DS-1-like G2P[4], bovine-like human, and/or bovine rotaviruses. Overall, the great genomic diversity among the DS-1-like G1P[8] strains seemed to have been generated through reassortment involving human and animal strains. To our knowledge, this is the first report on whole genome-based characterization of DS-1-like intergenogroup reassortant strains having G3P[8] and G2P[8] genotypes that have emerged in Thailand. Our observations will provide important insights into the evolutionary dynamics of emerging DS-1-like G1P[8] strains and related reassortant ones.

The emergence and rapid spread of unusual DS-1-like intergenogroup reassortant rotavirus strains have been recently reported in Asia, Australia, and Europe. During rotavirus surveillance in Thailand in 2013-2014, novel DS-1-like intergenogroup reassortant strains having G8P[8] genotypes (i.e., strains KKL-17, PCB-79, PCB-84, PCB-85, PCB-103, SKT-107, SWL-12, NP-130, PCB-656, SKT-457, SSKT-269, and SSL-55) were identified in stool samples from hospitalized children with severe diarrhea. In this study, we determined and characterized the complete genomes of these 12 strains (seven strains, KKL-17, PCB-79, PCB-84, PCB-85, PCB-103, SKT-107, and SWL-12, found in 2013 (2013 strains), and five, NP-130, PCB-656, SKT-457, SSKT-269, and SSL-55, in 2014 (2014 strains)). On full genomic analysis, all 12 strains showed a unique genotype constellation comprising a mixture of genogroup 1 and 2 genes: G8-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2. With the exception of the G genotype, the unique genotype constellation of the 12 strains (P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2) was found to be shared with DS-1-like intergenogroup reassortant strains. On phylogenetic analysis, six of the 11 genes of the 2013 strains (VP4, VP2, VP3, NSP1, NSP3, and NSP5) appeared to have originated from DS-1-like intergenogroup reassortant strains, while the remaining four (VP7, VP6, VP1, and NSP2) and one (NSP4) gene appeared to be of bovine and human origin, respectively. Thus, the 2013 strains appeared to be reassortant strains as to DS-1-like intergenogroup reassortant, bovine, bovine-like human, and/or human rotaviruses. On the other hand, five of the 11 genes of the 2014 strains (VP4, VP2, VP3, NSP1, and NSP3) appeared to have originated from DS-1-like intergenogroup reassortant strains, while three (VP7, VP1, and NSP2) and one (NSP4) were assumed to be of bovine and human origin, respectively. Notably, the remaining two genes, VP6 and NSP5, of the 2014 strains appeared to have originated from locally circulating DS-1-like G2P[4] human rotaviruses. Thus, the 2014 strains were assumed to be multiple reassortment strains as to DS-1-like intergenogroup reassortant, bovine, bovine-like human, human, and/or locally circulating DS-1-like G2P[4] human rotaviruses. Overall, the great genomic diversity among the DS-1-like intergenogroup reassortant strains seemed to have been generated through additional reassortment events involving animal and human strains. Moreover, all the 11 genes of three of the 2014 strains, NP-130, PCB-656, and SSL-55, were very closely related to those of Vietnamese DS-1-like G8P[8] strains that emerged in 2014-2015, indicating the derivation of these DS-1-like G8P[8] strains from a common ancestor. To our knowledge, this is the first report on full genome-based characterization of DS-1-like G8P[8] strains that have emerged in Thailand. Our observations will add to our growing understanding of the evolutionary patterns of emerging DS-1-like intergenogroup reassortant strains.

After an outbreak of leptospirosis in workers who participated in cleaning a pond during September 1999 in Thailand, a serologic survey was conducted. Among a cohort of 104 persons from one village who participated in pond cleaning activity, 43 (41.3%) were seropositive for immunoglobulin M antibodies against Leptospira, indicating recent infection. Only 17 (39.5%) of 43 seropositive persons reported a recent febrile illness; the remaining seropositive persons were considered asymptomatic, suggesting that asymptomatic leptospirosis infection may be common where leptospirosis is endemic. Multivariable logistic regression indicated that wearing long pants or skirts was independently protective against leptospirosis infection (ORadjusted = 0.217), while the presence of more than two wounds on the body was independently associated with infection (ORadjusted = 3.97). Educational efforts should be enhanced in areas where leptospirosis is endemic to encourage the use of protective clothing. In addition wound management and avoidance of potentially contaminated water when skin wounds are present should be included in health education programs.

Due to the widespread Omicron variant of SARS-CoV-2 in Thailand, the effectiveness of COVID-19 vaccines has become a major issue. The primary objective of this study is to examine the real-world effectiveness of COVID-19 vaccines based on secondary data acquired under normal circumstances in a real-world setting, to protect against treatment with invasive ventilation of pneumonia during January to April 2022, a period when Omicron was predominant. We conducted a nationwide test-negative case-control study. The case and control were matched with a ratio of 1:4 in terms of age, date of specimen collection, and hospital collection specimen and the odds ratio was calculated using conditional logistic regression. Overall, there was neither a distinction between mix-and-match regimens and homologous mRNA regimens against severe symptoms, nor was there a decline of the protective effect over the study period. The third and fourth dose boosters with ChAdOx1 nCoV-19 or mRNA vaccines provided high levels of protection against severe outcomes, approximately 87% to 100%, whereas two doses provided a moderate degree (70%). Thus, this study concludes that current national vaccine strategies provide favourable protective benefits against the Omicron variant. All Thais should receive at least two doses, while high-risk or vulnerable groups should be administered at least three doses.

The objective of this study is to explore the real-world effectiveness of various vaccine regimens to tackle the epidemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant in Thailand during September-December 2021. We applied a test-negative case control study, using nationwide records of people tested for SARS-CoV-2. Each case was matched with two controls with respect to age, detection date, and specimen collection site. A conditional logistic regression was performed. Results were presented in the form vaccine effectiveness (VE) and 95% confidence interval. A total of 1,460,458 observations were analyzed. Overall, the two-dose heterologous prime-boost, ChAdOx1 + BNT162b2 and CoronaVac + BNT162b2, manifested the largest protection level (79.9% (74.0-84.5%) and 74.7% (62.8-82.8%)) and remained stable over the whole study course. The three-dose schedules (CoronaVac + CoronaVac + ChAdOx1, and CoronaVac + CoronaVac + BNT162b2) expressed very high degree of VE estimate (above 80.0% at any time interval). Concerning severe infection, almost all regimens displayed very high VE estimate. For the two-dose schedules, heterologous prime-boost regimens seemed to have slightly better protection for severe infection relative to homologous regimens. Campaigns to expedite the rollout of third-dose booster shot should be carried out. Heterologous prime-boost regimens should be considered as an option to enhance protection for the entire population.

An unusual rotavirus strain with the G9P[23] genotype (RVA/Human-wt/THA/KKL-117/2014/G9P[23]) was identified in a stool specimen from a 10-month-old child hospitalized with severe diarrhoea. In this study, we sequenced and characterized the complete genome of strain KKL-117. On full-genomic analysis, strain KKL-117 was found to have the following genotype constellation: G9-P[23]-I5-R1-C1-M1-A8-N1-T1-E1-H1. The non-G/P genotype constellation of this strain (I5-R1-C1-M1-A8-N1-T1-E1-H1) is commonly shared with rotavirus strains from pigs. Furthermore, phylogenetic analysis indicated that each of the 11 genes of strain KKL-117 appeared to be of porcine origin. Our observations provide important insights into the dynamic interactions between human and porcine rotavirus strains.

The emergence and rapid spread of unusual DS-1-like intergenogroup reassortant rotavirus strains have been recently reported in Asia, Australia, and Europe. During rotavirus surveillance in Thailand in 2013-2014, novel DS-1-like intergenogroup reassortant strains having G8P[8] genotypes (i.e., strains KKL-17, PCB-79, PCB-84, PCB-85, PCB-103, SKT-107, SWL-12, NP-130, PCB-656, SKT-457, SSKT-269, and SSL-55) were identified in stool samples from hospitalized children with severe diarrhea. In this study, we determined and characterized the complete genomes of these 12 strains (seven strains, KKL-17, PCB-79, PCB-84, PCB-85, PCB-103, SKT-107, and SWL-12, found in 2013 (2013 strains), and five, NP-130, PCB-656, SKT-457, SSKT-269, and SSL-55, in 2014 (2014 strains)). On full genomic analysis, all 12 strains showed a unique genotype constellation comprising a mixture of genogroup 1 and 2 genes: G8-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2. With the exception of the G genotype, the unique genotype constellation of the 12 strains (P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2) was found to be shared with DS-1-like intergenogroup reassortant strains. On phylogenetic analysis, six of the 11 genes of the 2013 strains (VP4, VP2, VP3, NSP1, NSP3, and NSP5) appeared to have originated from DS-1-like intergenogroup reassortant strains, while the remaining four (VP7, VP6, VP1, and NSP2) and one (NSP4) gene appeared to be of bovine and human origin, respectively. Thus, the 2013 strains appeared to be reassortant strains as to DS-1-like intergenogroup reassortant, bovine, bovine-like human, and/or human rotaviruses. On the other hand, five of the 11 genes of the 2014 strains (VP4, VP2, VP3, NSP1, and NSP3) appeared to have originated from DS-1-like intergenogroup reassortant strains, while three (VP7, VP1, and NSP2) and one (NSP4) were assumed to be of bovine and human origin, respectively. Notably, the remaining two genes, VP6 and NSP5, of the 2014 strains appeared to have originated from locally circulating DS-1-like G2P[4] human rotaviruses. Thus, the 2014 strains were assumed to be multiple reassortment strains as to DS-1-like intergenogroup reassortant, bovine, bovine-like human, human, and/or locally circulating DS-1-like G2P[4] human rotaviruses. Overall, the great genomic diversity among the DS-1-like intergenogroup reassortant strains seemed to have been generated through additional reassortment events involving animal and human strains. Moreover, all the 11 genes of three of the 2014 strains, NP-130, PCB-656, and SSL-55, were very closely related to those of Vietnamese DS-1-like G8P[8] strains that emerged in 2014-2015, indicating the derivation of these DS-1-like G8P[8] strains from a common ancestor. To our knowledge, this is the first report on full genome-based characterization of DS-1-like G8P[8] strains that have emerged in Thailand. Our observations will add to our growing understanding of the evolutionary patterns of emerging DS-1-like intergenogroup reassortant strains., Competing Interests: The authors have declared that no competing interests exist.

The emergence and rapid spread of novel DS-1-like G1P[8] human rotaviruses in Japan were recently reported. More recently, such intergenogroup reassortant strains were identified in Thailand, implying the ongoing spread of unusual rotavirus strains in Asia. During rotavirus surveillance in Thailand, three DS-1-like intergenogroup reassortant strains having G3P[8] (RVA/Human-wt/THA/SKT-281/2013/G3P[8] and RVA/Human-wt/THA/SKT-289/2013/G3P[8]) and G2P[8] (RVA/Human-wt/THA/LS-04/2013/G2P[8]) genotypes were identified in fecal samples from hospitalized children with acute gastroenteritis. In this study, we sequenced and characterized the complete genomes of strains SKT-281, SKT-289, and LS-04. On whole genomic analysis, all three strains exhibited unique genotype constellations including both genogroup 1 and 2 genes: G3-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2 for strains SKT-281 and SKT-289, and G2-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2 for strain LS-04. Except for the G genotype, the unique genotype constellation of the three strains (P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2) is commonly shared with DS-1-like G1P[8] strains. On phylogenetic analysis, nine of the 11 genes of strains SKT-281 and SKT-289 (VP4, VP6, VP1-3, NSP1-3, and NSP5) appeared to have originated from DS-1-like G1P[8] strains, while the remaining VP7 and NSP4 genes appeared to be of equine and bovine origin, respectively. Thus, strains SKT-281 and SKT-289 appeared to be reassortant strains as to DS-1-like G1P[8], animal-derived human, and/or animal rotaviruses. On the other hand, seven of the 11 genes of strain LS-04 (VP7, VP6, VP1, VP3, and NSP3-5) appeared to have originated from locally circulating DS-1-like G2P[4] human rotaviruses, while three genes (VP4, VP2, and NSP1) were assumed to be derived from DS-1-like G1P[8] strains. Notably, the remaining NSP2 gene of strain LS-04 appeared to be of bovine origin. Thus, strain LS-04 was assumed to be a multiple reassortment strain as to DS-1-like G1P[8], locally circulating DS-1-like G2P[4], bovine-like human, and/or bovine rotaviruses. Overall, the great genomic diversity among the DS-1-like G1P[8] strains seemed to have been generated through reassortment involving human and animal strains. To our knowledge, this is the first report on whole genome-based characterization of DS-1-like intergenogroup reassortant strains having G3P[8] and G2P[8] genotypes that have emerged in Thailand. Our observations will provide important insights into the evolutionary dynamics of emerging DS-1-like G1P[8] strains and related reassortant ones.

Stored serum specimens, from four regions of Thailand, of healthy children attending well baby clinics and of healthy people with acute illnesses visiting outpatient clinics were randomly sampled and tested for IgG antibody to measles, mumps, and rubella (MMR). The immunity patterns of rubella and mumps fitted well with the history of rubella and MMR vaccination, seroprotective rates being over 85% among those aged over seven years. A high proportion of younger children acquired the infection before the age of vaccination. MMR vaccination should preferably be given to children at an earlier age. For measles, 73% seroprotective rates among children, aged 8-14 years, who should have received two doses of measles/MMR vaccine, were lower than expected. This finding was consistent with the age-group reported in outbreaks of measles in Thailand. The apparent ineffectiveness (in relation to measles) of MMR immunization of 1st grade students warrants further studies.

Tetanus is a disease with high mortality and the most important measure for effective prevention is vaccination. Tetanus immunization has been introduced to Thailand's national immunization program for 30 years. Yet, the coverage and seroprevalence of tetanus antibody in vast parts of the population has not been assessed. This study has been performed on 1,277 subjects aged between 6 months and 60 years or above from four geographically distinct provinces of Thailand. Tetanus antibody levels were measured using a commercially available ELISA kit. Most of the Thai population had immunity against tetanus. The level of antibodies to tetanus, as demonstrated by the geometric mean titer of antibody (GMT) (and 95% confidence interval) was 2.62 (2.34-2.91) IU/ml. The highest and lowest GMT was found in subjects aged between 5 and 9 years, and above 60 years of age with GMT (and 95% confidence intervals) of 3.64 (3.34-3.96) and 1.24 (0.67-2.29) IU/ml respectively. The minimum protective level of antitoxin (>0.01 IU/ml) was detected in 99.7 % of subjects. More than 90% of subjects displayed durable antibody protection levels (DAPL) (> or = 1.0 IU/ml), except for subjects above the age of 60 years (82%). According to this study, the majority of the population expresses tetanus antibody levels that can confer long term protection. Yet, considering the lowest GMT and the highest incidence of tetanus cases found in subjects aged above 60 years, re-immunization should be targeted at this age group especially if they had sustained any tetanus-prone injury.

HCV can be classified into 6 major genotypes based on the phylogenetic analysis of the genomic sequences. The 3 major genotypes found in Thailand are 3, 1 and 6, respectively. In 2004, an epidemiological survey was carried out to evaluate the seroprevalence of HCV infections among populations aged 2-60 years in four provinces of Thailand, representing the North, Northeast, Center and South of the country, respectively. One hundred and twenty five out of 5,825 serum samples (2.15%) were positive for anti-HCV by ELISA. Fifty eight out of 100 anti-HCV positive samples (58.0%) were positive by RT-PCR of the 5'UTR. The core region of 45 representative samples was sequenced allowing classification into genotype variants 1a (6.7%), 1b (26.7%), 2a (2.2%), 2c (2.2%), 3a (51.1%), 3b (2.2%) and 6 (8.9%). This information might be crucial for public health surveillance and prevention of HCV infection.

Objectives: To evaluate the impact of the universal hepatitis B (HB) vaccination programme on the prevalence of hepatitis B surface antigen (HBsAg) carriers and immunity to HB virus infection among children <18 years and to determine the HB seroprevalence in the Thai population., Methods: We enrolled people in four provinces, including Chiangrai, Udon Thani, Chonburi and Nakhon Si Thammarat to geographically represent populations in the North, Northeast, Center and South of the country respectively. Serology for HBsAg, anti-hepatitis B surface (anti-HBs), and anti-hepatitis B core (anti-HBc) was tested using ELISA commercial kits. In total, 6213 subjects aged 6 months to 60 years from the four provincial hospitals and two to three district hospitals of each participating province participated., Results: Overall HBsAg, anti-HBs, and anti-HBc seropositive rates amounted to 4%, 41.6% and 26.5% respectively. Of 2887 participants aged 6 months to 18 years, 2303 were born after (group I) and 584 prior to (group II) HB vaccine integration into the expanded programme on immunization of each participating province. The HBsAg seropositive rate was 0.7% among group I children and 4.3% among group II children. The prevalence rate of anti-HBc was 2.9% in group I and 15.8% in group II. In children under 18 years, the HBsAg carrier rate was 0.98% among complete vaccinees and 1.36% among participants without vaccination., Conclusions: This finding supports the efficacy of universal HB immunization in reducing the prevalence of HB infection in Thailand which is a highly endemic country.

After an outbreak of leptospirosis in workers who participated in cleaning a pond during September 1999 in Thailand, a serologic survey was conducted. Among a cohort of 104 persons from one village who participated in pond cleaning activity, 43 (41.3%) were seropositive for immunoglobulin M antibodies against Leptospira, indicating recent infection. Only 17 (39.5%) of 43 seropositive persons reported a recent febrile illness; the remaining seropositive persons were considered asymptomatic, suggesting that asymptomatic leptospirosis infection may be common where leptospirosis is endemic. Multivariable logistic regression indicated that wearing long pants or skirts was independently protective against leptospirosis infection (OR(adjusted) = 0.217), while the presence of more than two wounds on the body was independently associated with infection (OR(adjusted) = 3.97). Educational efforts should be enhanced in areas where leptospirosis is endemic to encourage the use of protective clothing. In addition, wound management and avoidance of potentially contaminated water when skin wounds are present should be included in health education programs.

Diphtheria remains endemic in developing countries, but there are limited published data on the subject. Thailand's diphtheria surveillance data are relatively complete and may give a fuller picture of the situation in similar countries. After routine immunization began in 1977, the incidence of reported diphtheria decreased by >98% to <0.1 case per 100,000 persons annually in the 1990s. Despite infant immunization coverage of >90%, diphtheria cases were reported throughout the 1990s, primarily among children <15 years old. Outbreaks were linked to both persistent endemic circulation and to importation of toxigenic Corynebacterium diphtheriae; suboptimal immunization coverage in minority and disadvantaged groups contributed. A serologic survey found 25% of adults 20-39 years old and 14% of adolescents 10-19 years old lacked immunity to diphtheria; these data indicate an accumulation of susceptible adolescents and adults. Diphtheria remains a threat in Thailand; improvements in diphtheria control will depend on improving childhood immunization coverage in Thailand and the surrounding region.