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

alexandrossfakianakis shared this article with you from Inoreader Effects of boosted mRNA and adenoviral‐vectored vaccines on immune responses to omicron BA.1 and BA.2 following the heterologous CoronaVac/AZD1222 vaccination via Journal of Medical Virology Abstract Introduction The coronavirus 2019 omicron variant has surged rapidly and raises concerns about immune evasion even in individuals with complete vaccination because it harbors mutations. Here, we examine the capability of booster vaccination following CoronaVac/AZD1222 prime to induce neutralizing antibodies (NAbs) against omicron (BA.1 and BA.2) and T-cell responses. Methods A total of 167 participants primed with heterologous CoronaVac/AZD1222 for 4-5 months were enrolled to receive AZD1222, BNT162b2, or mRNA-1273 as a third dose. Reactogenicity was recorded. Immunogenicity analyses of SARS-CoV-2 binding antibodies were measured using ELISA. The neutralizing antibody (NAb) titers against omicron BA.1 and BA.2 were determined using the focus reduction neutralization test (FRNT50) and total interferon-gamma (IFN-γ) responses were measured to observe the T cell activation. Results A 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. In addition, individuals boosted with mRNA vaccines develop a T cell response to spike protein while those boosted with AZD1222 did not. Reactogenicity was mild to moderate without serious adverse events. Conclusions Our findings demonstrated that mRNA booster vaccination is able to overcome waning immunity to provide antibodies that neutralize omicron BA.1 and BA.2, as well as a T cell response. This article is protected by copyright. All rights reserved. View on Web

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