Effects of boosted mRNA and adenoviral-vectored vaccines on immune responses to omicron BA.1 and BA.2 following the heterologous CoronaVac/AZD1222 vaccination

Abstract

AbstractBackgroundThe coronavirus 2019 omicron variant has surged rapidly and raises concerns about immune evasion because it harbors mutations even in individuals with complete vaccination. Here, we examine the capability of the booster vaccination to induce neutralizing antibodies (NAbs) against omicron (BA.1 and BA.2) and T-cell responses.MethodsA total of 167 participants primed with heterologous CoronaVac/AZD1222 were enrolled to receive AZD1222, BNT162b2, or mRNA-1273 as a booster dose. Reactogenicity was recorded. Binding antibody, neutralizing antibody (NAb) titers against omicron BA.1 and BA.2, and total interferon gamma (IFN-γ) post-booster responses were measured.ResultsA substantial loss in neutralizing potency to omicron variant was found at 4 to 5 months after receiving the heterologous CoronaVac/AZD1222. Following booster vaccination, a significant increase in binding antibodies and neutralizing activities toward delta and omicron variants was observed. Neutralization to omicron BA.1 and BA.2 were comparable, showing the highest titers after boosted mRNA-1273 followed by BNT162b2 and AZD1222. Notably, boosted individuals with mRNA vaccines could induce T cell response. Reactogenicity was mild to moderate without serious adverse events.ConclusionsOur findings highlight that the booster vaccination could overcome immunity wanes and provide adequate NAbs coverage against omicron BA.1 and BA.2.