Assawakosri S.Kanokudom S.Chansaenroj J.Suntronwong N.Auphimai C.Nilyanimit P.Vichaiwattana P.Thongmee T.Duangchinda T.Chantima W.Pakchotanon P.Srimuan D.Thatsanatorn T.Klinfueng S.Sudhinaraset N.Mongkolsapaya J.Wanlapakorn N.Honsawek S.Poovorawan Y.Mahidol University2023-06-182023-06-182022-09-01International Journal of Infectious Diseases Vol.122 (2022) , 793-80112019712https://repository.li.mahidol.ac.th/handle/123456789/85589Objectives: The SARS-CoV-2 Omicron variant presents numerous mutations potentially able to evade neutralizing antibodies (NAbs) elicited by COVID-19 vaccines. Therefore, this study aimed to provide evidence on a heterologous booster strategy to overcome the waning immunity against Omicron variants. Methods: Participants who completed the Oxford/AstraZeneca (hereafter AZD1222) vaccine dose for 5-7 months were enrolled. The reactogenicity and persistence of immunogenicity in both humoral and cellular response after a homologous or heterologous booster with the AZD1222 and messenger RNA (mRNA) vaccines (BNT162b2, full, or half-dose mRNA-1273) administered 6 months after primary vaccination were determined. Results: A total of 229 individuals enrolled, and waning of immunity was observed 5-7 months after the AZD1222-primed vaccinations. Total receptor-binding domain (RBD) immunoglobulin (Ig) levels, anti-RBD IgG, and focus reduction neutralization test against Omicron BA.1 and BA.2 variants and T cell response peaked at 14-28 days after booster vaccination. Both the full and half dose of mRNA-1273 induced the highest response, followed by BNT162b2 and AZD1222. At 90 days, the persistence of immunogenicity was observed among all mRNA-boosted individuals. Adverse events were acceptable for all vaccines. Conclusion: A heterologous mRNA booster provided a significantly superior boost of binding and NAbs levels against the Omicron variant compared with a homologous booster in individuals with AZD1222-primed vaccinations.MedicineArticleSCOPUS10.1016/j.ijid.2022.07.0382-s2.0-851352719391878351135863731