Persistence of immunity against Omicron BA.1 and BA.2 variants following homologous and heterologous COVID-19 booster vaccines in healthy adults after a two-dose AZD1222 vaccination
Suvichada Assawakosri, Sitthichai Kanokudom, Jira Chansaenroj, Nungruthai Suntronwong, Chompoonut Auphimai, Pornjarim Nilyanimit, Preeyaporn Vichaiwattana, Thanunrat Thongmee, Thaneeya Duangchinda, Warangkana Chantima, Pattarakul Pakchotanon, Donchida Srimuan, Thaksaporn Thatsanatorn, Sirapa Klinfueng, Natthinee Sudhinaraset, Juthathip Mongkolsapaya, Nasamon Wanlapakorn, Sittisak Honsawek, Yong Poovorawan
Abstract
OBJECTIVES: 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.