Antibody response after a single dose of BBV152 vaccine negatively correlates with pre-existing antibodies and induces a significant but low levels of neutralizing antibodies to Omicron variant

Abstract

ABSTRACTMost adults in India have received at least one dose of COVID-19 vaccine and also been infected naturally during the pandemic. As immunization of individuals continues under this situation where the virus has attained endemicity, we assessed whether this hybrid immunity is further boosted by a single dose of BBV152, an inactivated SARS-CoV-2 vaccine, and, if these antibodies can neutralize SARS-CoV-2 delta and omicron variants. We found that natural infection during the second wave in 2021 led to generation of neutralizing antibodies against other lineages of SARS-CoV-2 including the omicron variant, albeit at a significantly lower level for the latter. A single dose of BBV152 boosted antibody titers against the delta and the omicron variants but the antibody levels remained low for the omicron variant. Boosting of antibodies showed negative correlation with baseline neutralizing antibody titers suggesting anergy of the immune system in individuals with high levels of antibodies.