ABSTRACT
The CoronaVac (Sinovac Biotech) and ChAdOx1(Oxford-AstraZeneca) are two widely used COVID-19 vaccines. We examined the immunogenicity of four COVID-19 booster vaccine: BBIBP-CorV (Sinopharm Biotech), ChAdOx1, 30g-BNT162b2 and 15g-BNT162b2 (Pfizer-BioNTech), in healthy adults who received a two-dose CoronaVac or ChAdOx1 8-12 weeks earlier. Among the 352 participants (179 CoronaVac and 173 ChAdOx1 participants), 285 (81%) were female, and median age was 39(IQR: 31-47) years. 98%(175/179) and 99%(172/173) of Coronavac and ChAdOx1 participants remained seropositive at baseline. Two weeks post-booster, both 30g- and 15g-BNT162b2 induced the highest anti-RBD IgG concentration (BAU/mL); Coronavac-prime: 30g-BNT162b2, 5152.2(95%CI 4491.7-5909.8); 15g-BNT162b2, 3981.1(3397.2-4665.4); ChAdOx1, 1358.0(1141.8-1615.1); BBIBP-CorV, 154.6(92.11-259.47); ChAdOx1-prime: 30g-BNT162b2, 2363.8(2005.6-2786.1; 15g-BNT162b2, 1961.9(1624.6-2369.1); ChAdOx1, 246.4(199.6-304.2); BBIBP-CorV, 128.1(93.5-175.4). Similarly, both 30g- and 15g-BNT162b2 boosting induced the highest neutralizing antibodies (nAb) titres against all variants and highest T-cell response evaluated by interferon gamma released asssays. While all BNT162b2 or heterologous ChAdOx1-boosted participants had nAb against Omicron, these were <50% for BBIBP-CorV and 75% for homologous ChAdOx1-boosted participants. There was significant decrease in nAb (>4-fold) 16-20 weeks post booster. Heterologous boosting with BNT162b2 following CoronaVac or ChAdOx1 primary series is most immunogenic. A lower dose BNT162b2 may be considered as booster in settings with limited vaccine supply.
ABSTRACT
To evaluate the performance of interferon gamma release assays and tuberculin skin test in Bacillus Calmette-Guerin vaccinated young children. Methods: A cross-sectional study was conducted in healthy children younger than 5 years who were recently diagnosed with tuberculosis or had recent exposure to active tuberculosis. QuantiFERON-TB Gold, T-SPOT.TB and tuberculin skin test were performed in each patient. Results: Of the 60 children, median age 3.3 years, 17 had tuberculosis and 43 had recent tuberculosis exposure. Overall, 15 (25.0%) children had tuberculin skin test reaction =10 mm; 8 (13.3%) were positive by QuantiFERON-TB Gold In-Tube test, and 12 (20.0%) by T-SPOT.TB. Nineteen (31.7%) children had at least one positive test. There was a moderate agreement between interferon gamma release assays and tuberculin skin test. Conclusions: The positive rates of interferon gamma release assays and tuberculin skin test were low in young children who were infected with tuberculosis, supporting the management strategy of not testing children younger than 5 years. (IGRA) do not react to BCG and most NTM[2], are preferred to TST in older children and adults[3], but may be less reactive in young children with immature T-cell function. Due to the limited knowledge of IGRA in BCG-vaccinated young children, we evaluated the performance and correlation of IGRA tests and TST in young children in a high TB burden setting who received BCG vaccination at birth and recently diagnosed with LTBI, or with active TB.
