Safety and Immunogenicity of a New Inactivated Polio Vaccine Made From Sabin Strains: A Randomized, Double-Blind, Active-Controlled, Phase 2/3 Seamless Study.

BACKGROUND: A new inactivated polio vaccine made from Sabin strains (sIPV) was developed as part of the global polio eradication initiative. METHODS: This randomized, double-blind, active-controlled, phase 2/3 seamless study was conducted in 2 stages. Healthy infants aged 6 weeks were randomly assigned to receive 3 doses of 1 of 4 study vaccines at 6, 10, and 14 weeks of age (336 received low-, middle-, or high-dose sIPV, or conventional IPV [cIPV] in stage I, and 1086 received lot A, B, or C of the selected sIPV dose, or cIPV in stage II). The primary outcome was the seroconversion rate 4 weeks after the third vaccination. RESULTS: In stage I, low-dose sIPV was selected as the optimal dose. In stage II, consistency among the 3 manufacturing lots of sIPV was demonstrated. The seroconversion rates for Sabin and wild strains of the 3 serotypes after the 3-dose primary series were 95.8% to 99.2% in the lot-combined sIPV group and 94.8% to 100% in the cIPV group, proving the noninferiority of sIPV compared to cIPV. No notable safety risks associated with sIPV were observed. CONCLUSIONS: Low-dose sIPV administered as a 3-dose vaccination was safe and immunogenic compared to cIPV. CLINICAL TRIALS REGISTRATION: NCT03169725.

Incidence of Respiratory Syncytial Virus Lower Respiratory Tract Infections During the First 2 Years of Life: A Prospective Study Across Diverse Global Settings.

BACKGROUND: The true burden of lower respiratory tract infections (LRTIs) due to respiratory syncytial virus (RSV) remains unclear. This study aimed to provide more robust, multinational data on RSV-LRTI incidence and burden in the first 2 years of life. METHODS: This prospective, observational cohort study was conducted in Argentina, Bangladesh, Canada, Finland, Honduras, South Africa, Thailand, and United States. Children were followed for 24 months from birth. Suspected LRTIs were detected via active (through regular contacts) and passive surveillance. RSV and other viruses were detected from nasopharyngeal swabs using PCR-based methods. RESULTS: Of 2401 children, 206 (8.6%) had 227 episodes of RSV-LRTI. Incidence rates (IRs) of first episode of RSV-LRTI were 7.35 (95% confidence interval [CI], 5.88-9.08), 5.50 (95% CI, 4.21-7.07), and 2.87 (95% CI, 2.18-3.70) cases/100 person-years in children aged 0-5, 6-11, and 12-23 months. IRs for RSV-LRTI, severe RSV-LRTI, and RSV hospitalization tended to be higher among 0-5 month olds and in lower-income settings. RSV was detected for 40% of LRTIs in 0-2 month olds and for approximately 20% of LRTIs in older children. Other viruses were codetected in 29.2% of RSV-positive nasopharyngeal swabs. CONCLUSIONS: A substantial burden of RSV-LRTI was observed across diverse settings, impacting the youngest infants the most. Clinical Trials Registration. NCT01995175.

Necrotizing fasciitis: a rare manifestation of late-onset neonatal group B streptococcal infection.

Preterm infants have a risk factor of developing late-onset group B streptococcal (GBS) infection. A 62-day-old infant who was a former 25-week male infant presented with fever and an erythematous, warm and tender, soft tissue swelling in the right submandibular region. He was diagnosed with cellulitis. Within 72 hours, his lesion had rapidly progressed to necrotizing fasciitis. His blood culture grew penicillin-sensitive GBS. This reported case illustrates necrotizing fasciitis as a rare manifestation of late-onset neonatal GBS infection.

Population Attributable Risk of Wheeze in 2-<6-Year-old Children, Following a Respiratory Syncytial Virus Lower Respiratory Tract Infection in The First 2 Years of Life.

BACKGROUND: There is limited evidence regarding the proportion of wheeze in young children attributable to respiratory syncytial virus lower respiratory tract infections (RSV-LRTI) occurring early in life. This cohort study prospectively determined the population attributable risk (PAR) and risk percent (PAR%) of wheeze in 2-<6-year-old children previously surveilled in a primary study for RSV-LRTI from birth to their second birthday (RSV-LRTI<2Y). METHODS: From 2013 to 2021, 2-year-old children from 8 countries were enrolled in this extension study (NCT01995175) and were followed through quarterly surveillance contacts until their sixth birthday for the occurrence of parent-reported wheeze, medically-attended wheeze or recurrent wheeze episodes (≥4 episodes/year). PAR% was calculated as PAR divided by the cumulative incidence of wheeze in all participants. RESULTS: Of 1395 children included in the analyses, 126 had documented RSV-LRTI<2Y. Cumulative incidences were higher for reported (38.1% vs. 13.6%), medically-attended (30.2% vs. 11.8%) and recurrent wheeze outcomes (4.0% vs. 0.6%) in participants with RSV-LRTI<2Y than those without RSV-LRTI<2Y. The PARs for all episodes of reported, medically-attended and recurrent wheeze were 22.2, 16.6 and 3.1 per 1000 children, corresponding to PAR% of 14.1%, 12.3% and 35.9%. In univariate analyses, all 3 wheeze outcomes were strongly associated with RSV-LRTI<2Y (all global P < 0.01). Multivariable modeling for medically-attended wheeze showed a strong association with RSV-LRTI after adjustment for covariates (global P < 0.0001). CONCLUSIONS: A substantial amount of wheeze from the second to sixth birthday is potentially attributable to RSV-LRTI<2Y. Prevention of RSV-LRTI<2Y could potentially reduce wheezing episodes in 2-<6-year-old children.

Dengue amid COVID-19 pandemic.

The increasing in dengue cases nowadays is a global threat concern. Fifty per cent of the world's population is vulnerable to dengue infection with Asia contributing over two-thirds of the global burden. The double trouble of Coronavirus disease 2019 (COVID-19) arising from novel severe respiratory syndrome coronavirus (SARS-CoV-2) and dengue virus is a major challenge, particularly in developing countries due to overburdened public health systems and economic constraints including the ability to diagnose. The objective of this study was to analyze the prevalence of dengue in Thailand during the outbreak of COVID-19. We studied data on dengue cases reported at epidemiological information centers, the Bureau of Epidemiology, and the Ministry of Public Health, Thailand during 2019 to 2021. Patients can be observed across all age groups, particularly adolescents and adults. Dengue was seen year-round, with highest incidence in the rainy seasons between June and September. Total number of cases was markedly declined by nearly 93 percentage from 2019 to 2011. Taken together, Thailand is still at risk of spreading of dengue in the midst of COVID-19 pandemic. Continuous status updates on dengue patients in Thailand should be incorporated into global health advisory on preventive measures before travelling.

Prevalence, risk factors, and vaccine effectiveness of COVID-19 infection in thai children, adolescents, and young adults in the omicron era.

Background and objectives: The study of prevalence, risk factors, and vaccine effectiveness (VE) in children, adolescents, and young adults during the Omicron era has been limited, making this the objectives of the study. Methods: A prospective, test-negative case-control study was conducted on patients aged 0-24 years old classified as patients under investigation (PUI) from January to May 2022. PUI with positive RT-PCR within 14 days were classified as cases, whilst PUI with negative RT-PCR in 14 days were controls. Univariate and multivariate analyses determined risk factors; VE was calculated using [1-adjusted odds ratio (OR)] × 100. Results: The final analyses included 3,490 patients with a PUI infection rate of 45.6%. Heterologous vaccination regimens, including inactivated vaccines, viral vectors, and mRNA were utilized during the study period. A total of 2,563 patients (73.5%) had received at least 2 vaccine doses, regardless of regimen. Male gender and household infections were independent risk factors for the development of infection, with an adjusted OR of 1.55 and 1.45, respectively. Underlying comorbidities and obesity were not significantly associated with the development of infection. Patients with underlying comorbidities were more likely to have at least moderate severity of infection with the adjusted OR of 3.07. Age older than 11 years was associated with lower infection risk and development of at least moderate infection with adjusted OR of 0.4 and 0.34, respectively. Vaccinated participants also had a lower risk of developing at least moderate infection: adjusted OR of 0.40. The adjusted VE of any vaccination regimen for infection prevention for one, two, three, or more than four doses was 21.8%, 30.6%, 53.5%, and 81.2%, respectively. The adjusted VE of any vaccination regimen for prevention of at least moderate severity of the disease for one, two, three, or more than four doses was 5.7%, 24.3% 62.9%, and 90.6%, respectively. Conclusion: Disease prevalence among PUI was substantially high during the Omicron wave. A two-dose vaccination regimen does not appear sufficient to ensure protection against infection.

Prevalence and associating factors of long COVID in pediatric patients during the Delta and the Omicron variants.

Introduction: The number of pediatric COVID-19 infections is increasing; however, the data on long COVID conditions in children is still limited. Our study aimed to find the prevalence of long COVID in children during the Delta and Omicron waves, as well as associated factors. Methods: A single-center prospective cohort study was conducted. We included 802 RT-PCR-confirmed COVID-19 pediatric patients in the Delta and Omicron periods. Long COVID was defined as having symptoms for ≥3 months after infection. Parents and/or patients were interviewed by phone. Multivariable logistic regression was performed to find associated factors with long COVID. Results: The overall prevalence of long COVID was 30.2%. The Delta period had more prevalence than the Omicron (36.3% vs. 23.9%). Common symptoms for patients 0-3 years' old were loss of appetite, rhinorrhea, and nasal congestion. Conversely, patients 3-18 years' old had hair loss, dyspnea on exertion, rhinorrhea, and nasal congestion. However, there was no significant negative impact on daily life. Most symptoms improved after a 6-month follow-up. Factors associated with long COVID-19 conditions were infection during the Omicron period (adjusted OR: 0.54; 95% CI: 0.39-0.74, P < 0.001), fever (adjusted OR: 1.49, 95% CI: 1.01-2.20, P = 0.04) and rhinorrhea (adjusted OR: 1.47, 95% CI: 1.06-2.02, P = 0.02). Conclusion: Infection during the Omicron wave has a lower prevalence of long COVID. The prognosis is often favorable, and most symptoms gradually become less. However, pediatricians may schedule appointments to surveil long COVID in children with fever or rhinorrhea as an initial symptom.

The immunogenicity of an extended dosing interval of BNT162b2 against SARS-CoV-2 Omicron variant among healthy school-aged children, a randomized controlled trial.

OBJECTIVES: To evaluate the immunogenicity of an extended interval regimen of BNT162b2 among healthy school-age children. METHODS: A randomized-control trial conducted among healthy Thai children aged 5-11 years. Participants received two doses of BNT162b2 with an 8-week (extended dosing) vs 3-week interval. Immunogenicity was determined by neutralization test (NT) against the Omicron variant, surrogate virus NT (sVNT; BA.1, % inhibition), and pseudovirus NT (BA.2, the half-maximal inhibition dilution or ID50). The third dose was offered to participants who had sVNT <68% inhibition. The immunogenicity outcome was evaluated at 14 days after the second and third doses. RESULTS: During February to April 2022, 382 children with a median age (interquartile range) of 8.4 years (6.6-10.0) were enrolled. At 14 days, after two doses of BNT162b2, the geometric means of sVNT in 8-week vs 3-week interval groups were 49.6 (95% confidence interval [CI] 44.8-54.9) vs 16.5 (95% CI 13.0-20.9), with a geometric means ratio of 3.0 (95% CI 2.4-3.8). Among 102 participants who received the third dose at a median of 15 weeks from the second dose, the geometric means of sVNT increased to 73.3 (95% CI 69.0-77.8) and pseudovirus NT increased to 326 (95% CI 256-415). CONCLUSION: The extended 8-week interval regimen of BNT162b2 induced higher neutralizing antibodies than a standard 3-week interval regimen. The third dose induced high neutralizing antibodies against the Omicron variant.

Immunogenicity and Safety of the Third Booster Dose with mRNA-1273 COVID-19 Vaccine after Receiving Two Doses of Inactivated or Viral Vector COVID-19 Vaccine.

The changes in the severe acute respiratory syndrome coronavirus 2 and the tapering of immunity after vaccination have propelled the need for a booster dose vaccine. We aim to evaluate B and T cell immunogenicity and reactogenicity of mRNA-1273 COVID-19 vaccine (100 µg) as a third booster dose after receiving either two doses of inactivated COVID-19 vaccine (CoronaVac) or two doses of viral vector vaccine (AZD1222) in adults not previously infected with COVID-19. The anti-receptor-binding-domain IgG (anti-RBD IgG), surrogate virus neutralization test (sVNT) against the Delta variant, and Interferon-Gamma (IFN-γ) level were measured at baseline, day (D)14 and D90 after vaccination. In D14 and D90, the geometric means of sVNT were significantly increased to 99.4% and 94.5% inhibition in CoronaVac, respectively, whereas AZD1222 showed inhibition of 99.1% and 93%, respectively. Anti-RBD IgG levels were 61,249 to 9235 AU/mL in CoronaVac and 38,777 to 5877 AU/mL in AZD1222 after D14 and D90 vaccination. Increasing median frequencies of S1-specific T cell response by IFN-γ concentration were also elevated in D14 and were not significantly different between CoronaVac (107.8-2035.4 mIU/mL) and AZD1222 (282.5-2001.2 mIU/mL). This study provides evidence for the high immunogenicity of the mRNA-1273 booster after two doses of CoronaVac or AZD1222 in the Thai population.

Hybrid immunity from SARS-CoV-2 infection and mRNA BNT162b2 vaccine among Thai school-aged children.

Objective: To compare the immune response of hybrid immunity - arising from SARS-CoV-2 infection and mRNA BNT162b2 vaccination - to that of 2-doses of vaccine. Methods: In a subanalysis of BNT162b2 vaccine trial in 5 to 11-year-old children, There were 179 children who had hybrid immunity compared with 134 children with solely 2-dose vaccine. The immunological outcome was a surrogate virus neutralization test (sVNT) against the Omicron strain, BA.1, (%inhibition). An sVNT level ≥68 % inhibition was considered as protective immune response. Results: From February to April 2022, 179 children had COVID-19 natural infection resulting in hybrid immunity included: Group1;prior vaccination(n = 17), Group2;after the first dose(n = 61), and Group3;after the second dose(n = 97). The proportion of children with protective immune response was higher in Group 3 and Group 1 - 61.9 % and 58.8 %, compared to 36.1 % and 34.3 % in Group 2 and comparator group (2 doses of vaccine), respectively. The geometric mean % inhibition of sVNT was higher in Group 1 (68.5, 95 %CI 55.5-84.6) and Group 3 (63.5, 95 %CI 55.5-72.6), followed by comparator group (49.6, 95 %CI 44.8-54.9) and Group 2 (42.1, 95 %CI 34.6-51.3), p < 0.001. Conclusions: Immune response that arises from BNT162b2 vaccine after natural infection and infection after 2 doses of BNT162b2 was higher than infection after partially-vaccinated children.

Real-life effectiveness of COVID-19 vaccine during the Omicron variant-dominant pandemic: how many booster doses do we need?

The surge in coronavirus disease 2019 (COVID-19) caused by the Omicron variants of the severe acute respiratory syndrome coronavirus 2 necessitates researches to inform vaccine effectiveness (VE) and other preventive measures to halt the pandemic. A test-negative case-control study was conducted among adults (age ≥18 years) who were at-risk for COVID-19 and presented for nasopharyngeal real-time polymerase chain reaction testing during the Omicron variant-dominant period in Thailand (1 January 2022-15 June 2022). All participants were prospectively followed up for COVID-19 development for 14 days after the enrolment. Vaccine effectiveness was estimated and adjusted for characteristics associated with COVID-19. Of the 7971 included individuals, there were 3104 cases and 4867 controls. The adjusted VE among persons receiving 2-dose, 3-dose, and 4-dose vaccine regimens for preventing infection and preventing moderate-to-critical diseases were 33%, 48%, 62% and 60%, 74%, 76%, respectively. The VE were generally higher among those receiving the last dose of vaccine within 90 days compared to those receiving the last dose more than 90 days prior to the enrolment. The highest VE were observed in individuals receiving the 4-dose regimen, CoronaVac-CoronaVac-ChAdOx1 nCoV-19-BNT162b2 for both preventing infection (65%) and preventing moderate-to-critical diseases (82%). Our study demonstrated increased VE along with an increase in number of vaccine doses received. Current vaccination programmes should focus on reducing COVID-19 severity and mandate at least one booster dose. The heterologous boosters with viral vector and mRNA vaccines were highly effective and can be used in individuals who previously received the primary series of inactivated vaccine.

Evaluation of Clinical Case Definitions for Respiratory Syncytial Virus Lower Respiratory Tract Infection in Young Children.

BACKGROUND: Various case definitions of respiratory syncytial virus lower respiratory tract infection (RSV-LRTI) are currently proposed. We assessed the performance of 3 clinical case definitions against the World Health Organization definition recommended in 2015 (WHO 2015). METHODS: In this prospective cohort study conducted in 8 countries, 2401 children were followed up for 2 years from birth. Suspected LRTIs were detected via active and passive surveillance, followed by in-person clinical evaluation including single timepoint respiratory rate and oxygen saturation (by pulse oximetry) assessment, and nasopharyngeal sampling for RSV testing by polymerase chain reaction. Agreement between case definitions was evaluated using Cohen's κ statistics. RESULTS: Of 1652 suspected LRTIs, 227 met the WHO 2015 criteria for RSV-LRTI; 73 were classified as severe. All alternative definitions were highly concordant with the WHO 2015 definition for RSV-LRTI (κ: 0.95-1.00), but less concordant for severe RSV-LRTI (κ: 0.47-0.82). Tachypnea was present for 196/226 (86.7%) WHO 2015 RSV-LRTIs and 168/243 (69.1%) LRTI/bronchiolitis/pneumonia cases, clinically diagnosed by nonstudy physicians. Low oxygen saturation levels were observed in only 55/226 (24.3%) WHO 2015 RSV-LRTIs. CONCLUSIONS: Three case definitions for RSV-LRTI showed high concordance with the WHO 2015 definition, while agreement was lower for severe RSV-LRTI. In contrast to increased respiratory rate, low oxygen saturation was not a consistent finding in RSV-LRTIs and severe RSV-LRTIs. This study demonstrates that current definitions are highly concordant for RSV-LRTIs, but a standard definition is still needed for severe RSV-LRTI. CLINICAL TRIAL REGISTRATION: NCT01995175.

Pandemic influenza (H1N1) 2009 of pediatric patients at Thammasat University Hospital.

BACKGROUND: An emerge of pandemic influenza H1N1 2009 has devastated the global community. Pediatric population is among the groups with high attack rate. OBJECTIVE: To study the clinical presentation of pediatric patients (0-15 years old) infected with influenza H1N1 2009 and to evaluate the sensitivity and specificity of the rapid influenza test. MATERIAL AND METHOD: Retrospective data was collected from the medical reports of patients presenting with influenza like illness (ILI) whose samples from nasal swab were tested for H1N1 using reverse transcription polymerase chain reaction (RT-PCR) during June-September 2009 at the Thammasat University Hospital. RESULTS: Of 68 patients, 26 were confirmed to have H1N1 2009 strain. Of these, 61.5% were older than 5 years old; 26.9% had underlying conditions and 38.4% had hospitalization. All 26 patients presented with fever and cough; 73% had coryza; 57.6% had sore throat; and 88.4% had injected throat. Six patients (23%) had pneumonia. Patients younger than 5 years old experienced dyspnea and had abnormal results of a chest radiograph significantly more often than patients older than 5. Patients with H1N1 2009 strain were more likely to have sore throat, myalgia, and injected throat than non H1N1 2009 group. However chest wall retraction and abnormal chest radiograph were found significantly less often in the H1N1 group compared to the non-H1N1. No death case was reported. The rapid influenza test was found to have sensitivity of 80%, specificity of 64%, positive predictive value of 74.5%, and negative predictive value of 84.3% when compared to RT-PCR method. CONCLUSION: During pandemic period, older children with influenza like illness had novel H1N1 2009 infection more than younger children. The majority of pediatric patients presented with mild symptoms. Patients aged below 5 years more frequently experienced pneumonia. The rapid influenza test showed a high sensitivity but low specificity.

The clinical features, risk of prolonged hospitalization and household infections of hospitalized children for pandemic 2009 influenza A (H1N1) virus infection in Thailand.

OBJECTIVE: To evaluate the clinical features, risk of prolonged hospitalization, and household infection in Thai children hospitalized with 2009 pandemic influenza A/H1N1 virus (pH1N1). MATERIAL AND METHOD: The authors conducted a retrospective chart review of children hospitalized in four Thai tertiary care hospitals between June 1 and September 30, 2009, with reverse-transcriptase-polymerase-chain-reaction confirmed pH1N1. Household contact data were obtained by telephone. RESULTS: Pediatric admissions numbered 115, 58 were females (50.4%). Median age was 5.2 (range 0.5 to 15) years. Fifty-one (44.4%) children had underlying diseases, most commonly asthma 17 (14.8%). Median preadmission illness duration was two days (range 1 to 10). Sixty-one (53.0%) children had lymphopenia. Chest X-ray infiltration was detected in 89 (77.4%) children. Oseltamivir was prescribed in 104 (90.4%) children; 47(45.2%) within 48 hours of illness. 70 (60.9%) children received antibiotics. The median hospitalization was three days (range 1 to 94). Independent (multivariate analysis) factors associated with prolonged hospitalization (> or = 7 days) were aged five to nine years (OR 7.4; 95% CI 1.1-48.9, p = 0.037) and having an underlying disease (OR 5.9; 95% CI 1.5-23.3, p = 0.01). Five (4.3%) children required mechanical ventilation; two (1.7%) children died. Household data showed that 63 of 109 (57.8%) patients had contact with a suspected or confirmed pH1N1 case. There were 39 (15.7%) of 249 household contacts who were probable secondary cases: 23 suspected and 16 confirmed pH1N1 of whom 25 (64.1%) were aged < or = 18 years. CONCLUSION: Most pH1N1 infected hospitalized children had pneumonia, an uneventful short hospitalization, and a low in hospital mortality. Half of the patients were household acquired. Secondary household cases affected mostly children.

An epidemiological study of pediatric COVID-19 in the era of the variant of concern.

BACKGROUND: There were limited epidemiological data of pediatric COVID-19 in Asia outside China, especially during the era of the variants of concern such as the Delta and Alpha variants. The objective was to describe the clinical epidemiology of pediatric COVID-19 in a tertiary care center in Thailand from April to August 2021. The identification of risk factors for the development of pneumonia in these children was also performed. METHODS: This retrospective cohort study was conducted by retrospective chart review of all children aged 0-15 years admitted to Thammasat University Hospital care system during the study period. The risk factors for the development of pneumonia were analyzed using logistic regression. RESULTS: A total of 698 children were included for analysis, of which 52% were male. The mean age of the cohort was 7.2 + 4.5 years old. Radiographic pneumonia was identified in 100 children (14.3%) and a total of 16 children (2.3%) were diagnosed with severe and critical diseases. The mortality rate was 0.1%. Children younger than 1 year and children with comorbidity were at higher risk of developing pneumonia (Adjusted odds ratios 2.99 (95% confidence interval (CI): 1.56-5.74) and 2.32 (95% CI: 1.15-4.67), respectively). CONCLUSION: In the era of the variants of concern, the proportion of children with severe and critical diseases remained low. However, prudence must be taken in caring for younger children and children with comorbidity.

Immunogenicity and Reactogenicity of mRNA BNT162b2 COVID-19 Vaccine among Thai Adolescents with Chronic Diseases.

Adolescents with underlying diseases are at risk of severe COVID-19. The immune response of BNT162b2 may be poor among immunocompromised adolescents. We aim to describe immunogenicity of mRNA BNT162b2 among adolescents who are immunocompromised or have chronic diseases. We recruited adolescents 12-18 years of age; group A impaired-immunity (post-transplantation, cancer, on immunosuppressive drugs) and group B chronic diseases. A two-dose regimen of BNT162b2 was given. Immunogenicity was determined by surrogate virus neutralization test (sVNT) and IgG against receptor-binding domain (RBD). From August to October 2021, 312 adolescents, with a median age (IQR) of 15 years (13.7-16.5), were enrolled (group A 100, group B 212). The geometric means (GMs) of sVNT (% inhibition) against Delta strain and anti-RBD IgG (BAU/mL) after the 2nd dose among group A were: post-transplantation recipients 52.9 (95% CI 37.7-74.2) and 233.6 (95% CI 79-690.6); adolescents with cancer 62.3 (95% CI 29.2-133.1) and 214.9(95% CI 34.2-1348.6); and adolescents with other immunosuppressive conditions 66.7 (95% CI 52.4-84.8) and 849.8 (95% CI 393.4-1835.8). In group B were: adolescents living with HIV 98 (95% CI 97.3-98.8) and 3240.3 (95% CI 2699-3890.2), and adolescents with other chronic disease 98.6 (95% CI 98.3-98.9) and 3818.5 (95% CI 3490.4-4177.4). At day 90, immunity declined; among impaired-immunity participants were 43.9 (95% CI 30.8-62.4) and 178.7 (95% CI 91.2-350.1) and adolescents with chronic diseases were 90.6 (95% CI 88.4-92.8) and 1037.1 (95% CI 933.3-1152.5). In conclusion, adolescents with impaired immunity had a poor response to 2-doses of BNT162b2, additional dose should be considered. Adolescents with chronic diseases had excellent response but immunity waned after 3 m, booster dose may be required.

Immunogenicity to SARS-CoV-2 Omicron variant among school-aged children with 2-dose of inactivated SARS-CoV-2 vaccines followed by BNT162b2 booster.

Background: A primary series of 2-dose SARS-CoV-2 vaccines based on an ancestral strain generate inadequate neutralizing antibodies against the SARS-CoV-2 Omicron variant. This study aimed to describe the immune response from giving healthy school-aged children who previously received 2 inactivated vaccines an mRNA BNT162b2 booster. Methods: Healthy children aged 5-11 years who received 2 doses of CoronaVac or Covilo were enrolled and received 10 µg BNT162b2 intramuscularly. Neutralizing antibody against Omicron variant was measured at pre-booster and 14-21 days post-booster by surrogate virus neutralization test (sVNT, %inhibition) and pseudovirus neutralization test (pVNT, ID50). Antibody responses were compared with a parallel cohort of children who received 2 doses of BNT162b2 3 weeks apart. Results: From April to May 2022, 59 children with a mean age (SD) of 8.5 years (1.7) were enrolled: 20 CoronaVac and 39 Covilo recipients. The median interval from the primary series was 49 days (IQR 33-51). After booster, the geometric means (GMs) of sVNT and pVNT were 72.2 %inhibition (95 %CI 67.2-77.6) and 499 (95 %CI 399-624), respectively. The proportion of children with sVNT against Omicron strain ≥68 %inhibition increased from none to 70.2 %. The geometric mean ratio (GMR) of sVNT and pVNT compared with a parallel cohort were 4.3 and 12.2, respectively. The GMR of sVNT and pVNT between children who received booster dose at >6-week interval were 1.2 (95 %CI 1.1-1.3). and 1.8 (95 %CI 1.2-2.7) compared with 4-6 weeks interval. Conclusion: A regimen of 2-dose of inactivated vaccine followed by BNT162b2 booster dose elicited high neutralizing antibody against the Omicron variants in healthy school-aged children.

Low Measles Seropositivity Rate among Thai Adolescents in the Thai National Immunization Program.

To achieve the goal of measles elimination, herd immunity with 95% seroprotection in the community is required. This study aimed to describe the measles seropositivity rate among Thai children and adolescents. A cross-sectional study was conducted among children aged 3−18 years in Bangkok and its suburbs. Measles IgG antibodies were measured using a EUROIMMUN enzyme-linked immunosorbent assay kit. Seropositivity is defined as a measles IgG titer of ≥200 IU/L, due to a correlation with a >85% positive rate with a plaque reduction neutralizing titer of >120. Factors associated with seropositivity were analyzed using logistic regression analysis. From May to July 2020, 570 children with a median (IQR) age of 11.7 (9.4−14.8) years were enrolled. The geometric mean titer (GMT) of anti-measles IgG was 281 IU/L (95% CI; 257−306). The proportion of children with seropositivity was inversely correlated with age; 3−5 years 85.3%, 6−9 years 72.5%, 10−14 years 50.7%, and 15−18 years 56.3%. Adolescents aged 10−18 years had a lower measles seropositivity rate compared with young children; aOR 0.29 (95% CI 0.17−0.48). Only half of the adolescents who received two doses of measles-containing vaccine maintained measles IgG above the seropositive level. A measles booster dose for young adults may be needed to achieve the measles elimination goal.

Seroprevalence of mumps among children and adolescents in Thailand, 2020.

Thailand has implemented single-dose mumps-containing vaccines since 1997 and two doses since 2010. This study aimed to describe the seroprevalence of mumps among children who received one- or two-dose mumps vaccines. A cross-sectional study of 145 children (aged 3-9 years) and 422 adolescents (10-18 years) was conducted. Mumps IgG seropositivity was defined as ≥ 22 RU/mL by EUROIMMUN ELISA method. The mumps seroprevalence was higher in children (82.1%, 95% CI 74.8-87.9) compared to adolescents (41.7%, 95% CI 37.0-46.6) who had received at least one dose of the mumps vaccine. Among those receiving 2 doses of mumps vaccine at ≥ 5 years after their last mumps vaccination, only 51.3% had maintained IgG ≥ 22 RU/ml. There was a reverse correlation between mumps IgG titer and the time interval from the second dose of mumps vaccine (R = -0.44, p < 0.001). A booster dose of MMR vaccine in young adults may be needed.

Epidemiological and Clinical Characteristics of Pediatric COVID-19 in the Tertiary Care System in Thailand: Comparative Delta and pre-Delta Era.

Background: Few studies had focused on the epidemiological and clinical characteristics of pediatric COVID-19 (SARS-CoV-2) during Delta and pre-Delta eras in Asia, despite it being a pandemic. Objective: To study the epidemiological and clinical characteristics of three waves of pediatric COVID-19 infections in a tertiary-care setting in Thailand. Methods: This retrospective study reviewed all PCR-confirmed pediatric (0-18 years of age) COVID-19 infections between January 13, 2020, and October 31, 2021, in a tertiary care system in Thailand. Results: 1,019 patients, aged 0.02 - 18 years, 552 (54.2%) male, and 467 (45.8%) female, with a median age of 9.2 years, were enrolled. Asymptomatic cases accounted for 35.7%, of which 106 (18.9%) had abnormal chest X-ray findings. Most cases were classified as having mild clinical symptoms, with only 8 (0.8%) and 4 (0.4%) developing a severe and critical illness, respectively. There were no deaths. The Delta variant appeared more transmissible than previous ones, but we did not see any difference in disease severity. Upper respiratory tract symptoms were predominant, while few cases had lower respiratory tract involvement. The sensitivity and specificity of dyspnea symptoms to predict radiologically confirmed pneumonia were 14% and 95%, respectively, with a likelihood ratio of 3.37. The overall prognosis was good, with only 13 (1.3 %) needing respiratory support. All cases showed clinical improvement with a decent recovery. Conclusion: Pediatric COVID-19 during the Delta variant predominance era generally appeared more transmissible but benign. One-fifth of cases had pneumonia, but few cases needed respiratory support. Prevention remains important for disease control.