Assawakosri S.Kanokudom S.Suntronwong N.Auphimai C.Nilyanimit P.Vichaiwattana P.Thongmee T.Duangchinda T.Chantima W.Pakchotanon P.Srimuan D.Thatsanatorn T.Klinfueng S.Yorsaeng R.Sudhinaraset N.Wanlapakorn N.Mongkolsapaya J.Honsawek S.Poovorawan Y.Mahidol University2023-06-182023-06-182022-10-15Journal of Infectious Diseases Vol.226 No.8 (2022) , 1372-138100221899https://repository.li.mahidol.ac.th/handle/20.500.14594/85451Background: The use of an inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine (CoronaVac) against SARS-CoV-2 is implemented worldwide. However, waning immunity and breakthrough infections have been observed. Therefore, we hypothesized that the heterologous booster might improve the protection against the delta and omicron variants. Methods: A total of 224 individuals who completed the 2-dose CoronaVac for 6 months were included. We studied reactogenicity and immunogenicity after a heterologous booster with the inactivated vaccine (BBIBP), the viral vector vaccine (AZD1222), and the messenger ribonucleic acid (mRNA) vaccine (both BNT162B2 and mRNA-1273). We also determined immunogenicity at 3- and 6-month boosting intervals. Results: The solicited adverse events were mild to moderate and well tolerated. Total receptor binding domain (RBD) immunoglobulin (Ig), anti-RBD IgG, focus reduction neutralization test (FRNT50) against delta and omicron variants, and T-cell response were highest in the mRNA-1273 group followed by the BNT162b2, AZD1222, and BBIBP groups, respectively. We also witnessed a higher total Ig anti-RBD in the long-interval than in the short-interval group. Conclusions: All 4 booster vaccines significantly increased binding and neutralizing antibodies in individuals immunized with 2 doses of CoronaVac. The present evidence may benefit vaccine strategies to thwart variants of concern, including the omicron variant.MedicineArticleSCOPUS10.1093/infdis/jiac0922-s2.0-851393439051537661335267040