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
BackgroundResponding to SARS-CoV-2 Delta variants escaped the vaccine-induced immunity and waning immunity from the inactivated whole virus vaccine, Thailand recently proposed a heterologous inactivated whole virus vaccine (CoronaVac) viral vector vaccine (ChAdOx1 nCoV-19) prime-boost vaccine regimen(I/V). This study aims to evaluate the immunogenicity and adverse events of this regimen by comparison with homologous CoronaVac, ChAdOx1 nCoV-19, and convalescent serum. MethodImmunogenicity was evaluated by the level of IgG antibodies against the receptor-binding domain of the SARS-CoV-2 spike protein (S1 subunit) (anti-S RBD). At 2 weeks following the second dosage, a selection of random samples was tested for plaque reduction neutralisation (PRNT) and Pseudotype-Based Microneutralization test (PVNT) against SARS-CoV-2 variants of concern (VOCs). The safety profile of heterologous CoronaVac-ChAdOx1 nCoV-19 prime-boost vaccine regimen was described by interviewing at the 1-month visit. ResultBetween April to August 2021,426 participants were included in the study, with 155 obtaining CoronaVac-ChAdOx1 nCoV-19(I/V),32 obtaining homologous CoronaVac(I/I),47 obtaining homologous ChAdOx1 nCoV-19(V/V),169 with history covid-19 infection. Geometric mean titers (GMTs) of anti-S RBD level in the I/V group compare 2wks and 4 wks (873.9 vs 639,p=0.00114).At 4 wks, GMTs of anti-S RBD level in I/V group was 639, 95% CI 63-726,and natural infection group 177.3, 95% CI 42-221, and V/V group 211.1, 95% CI 77-152, and I/I group 108.2, 95% CI 77-152; all p<0.001).At 2 wks, The GMTs of 50%PRNT of 19 sampling from the I/V group is 434.5, 95% CI 326-579, against wild type and 80.4, 95% CI 56-115, against alpha and 67.4, 95% CI 48-95, against delta and 19.8, 95% CI 14-30, against beta; all p<0.001. At 2 wks, The GMTs of 50%PVNT of 15 sampling from the I/V group is 597.8, 95% CI 368-970, against wild type and 163.9, 95% CI 89-301, against alpha and 157.7, 95% CI 66-378, against delta. The AEs in the I/V schedule were well tolerated and generally unremarkable. ConclusionThe I/V vaccination is a mixed regimen that induced higher immunogenicity and shall be considered for responding to Delta Variants when only inactivated whole virus vaccine and viral vector vaccine was available.