There are limited data regarding the immunogenicity of mRNA-based SARS-CoV-2 vaccine BNT162b2 among immunosuppressed or obese adolescents. We evaluated the humoral immune response in adolescents with obesity and adolescent liver transplant recipients (LTRs) after receiving two BNT162b2 doses. Sixty-eight participants (44 males; mean age 14.9 ± 1.7 years), comprising 12 LTRs, 24 obese, and 32 healthy adolescents, were enrolled. Immunogenicity was evaluated by anti-SARS-CoV-2 spike protein immunoassay and surrogate viral neutralization tests (sVNT) against the Delta and Omicron (BA.1) variants. At 27.1 ± 3.2 days after the second dose, the antibody levels were 1476.6 ± 1185.4, 2999.4 ± 1725.9, and 4960.5 ± 2644.1 IU/mL in the LTRs, obese adolescents, and controls, respectively (p < 0.001). Among obese individuals, liver stiffness <5.5 kPa was associated with higher antibody levels. The %inhibition of sVNT was significantly lower for the Omicron than that for the Delta variant. Injection site pain was the most common local adverse event. Nine participants (three obese and six controls) developed COVID-19 at 49 ± 11 days after the second vaccination; four were treated with favipiravir. All infections were mild, and the patients recovered without any consequences. Our study supports the need for the booster regimen in groups with an inferior immunogenic response, including LTRs and obese individuals.

Prior results investigating a correlation between obesity and hepatitis A virus (HAV) vaccine response have been inconclusive, with limited data involving live attenuated HAV vaccines. The aim of this study is to evaluate the effect of overweight and obesity on the response to live attenuated HAV vaccine in children and young adults. This prospective cohort study was conducted in Thailand with subjects ranging in age from seven to twenty-five years. The subjects were administered 0.5 mL of MEVAC™-A and tested for anti-HAV antibodies before and at 8–9 weeks after vaccination. Baseline seronegative subjects (anti-HAV antibodies < 20 mIU/mL) were divided into non-obese (underweight/normal weight) and obese (overweight/obesity/severe obesity) groups. A total of 212 (117 non-obese and 95 obese) subjects completed the study (mean age (SD) = 13.95 (3.90) years). The seroprotection rates were 100%. Postvaccination geometric mean titers (95% CI) were 429.51 (401.97, 458.94) and 467.45 (424.47, 514.79) mIU/mL in the non-obese and obese groups, respectively. Females (p = 0.013) and subjects with truncal obesity (p = 0.002) had significantly higher titers than other participants. Live attenuated HAV vaccine is safe and has comparably high immunogenicity in both underweight/normal weight and overweight/obese persons.

Background: Half of the pediatric liver transplantation (LT) patients developed at least one episode of infection within 6 months after LT. However, few studies reported infections and outcomes after pediatric LT in Thailand. We aim to examine the characteristics of infections and determine the factors associated with infections and clinical outcomes after pediatric LT. Methods: A retrospective cohort study was conducted in patients aged <18 years who had LT. Medical records were reviewed in the first-year posttransplantation. The risk factors for developing an infection, factors associated with infections and clinical outcomes were evaluated using logistic regression. Results: From January 2009 to August 2021, 99 cases who had pediatric LT were analyzed. The median (interquartile range) age was 14 months (10-46 months). All patients, except for four patients, completed their follow-up. There were 464 infection episodes within the first-year posttransplantation. The predominant infection sites were in the bloodstream (120, 25.9%) and gastrointestinal tract (68, 14.7%). Overall, bacterial infections accounted for 166 infections (35.7%). The most common bacterial pathogen was Escherichia coli (22.9%). The mean (SD) operative duration was 10 (±1.8) hours and 61.6% took more than 10 hours which was a factor significantly associated with infection post LT (odds ratio, 5.5; 95% confidence interval, 1.0-29.0). The 1-year survival rate post LT was 96.0%. Out of the 4 deaths, three patients died due to infections. Conclusions: The most common site of infection was in the bloodstream and Gram-negative bacterial infections developed in one-third of the recipients. Prolonged operative duration significantly increased the risk of developing infections post-LT.