LAUSR

BACKGROUND Covaxin/BBV152 is one of the most widely used vaccines against SARS-CoV-2 infection and one of the few vaccines used extensively in low- and middle-income countries (LMIC). METHODS We investigated the effect of Covaxin on the SARS-CoV-2 specific IgG and IgA and neutralizing antibody (NAb) levels at baseline (M0) and at months 1 (M1), 2 (M2), 3 (M3), 4 (M4), 6 (M6) and 12 (M12) following vaccination in health care workers. In addition, we also examined the NAb levels against variant lineages of B.1.617.2 (Delta, India), B.1.617.2.1 (Delta Plus, India), B.1.351 (Beta, SA), B.1.1.7 (Alpha, UK) and B.1.1.529 (Omicron).Results: Covaxin induces enhanced SARS-CoV-2 binding antibodies of IgG and IgA responses against both spike (S) and nucleocapsid (N) antigens at M1, M2, M3, M4, M6 and M12 in comparison to M0. Our data also reveal that NAb levels against the ancestral strain (Wuhan, Wild type) are elevated and sustained at M1, M2, M3, M4, M6 and M12 in comparison to M0 and against variant lineages of B.1.617.2 (Delta, India), B.1.617.2.1 (Delta Plus, India), B.1.351 (Beta, SA), B.1.1.7 (Alpha, UK) are elevated at M3, M6 and M12 in comparison to M0. However, NAb levels against B.1.1.529 (Omicron) was consistently below the limit of detection except at M12. CONCLUSION Thus, Covaxin induces an enhanced humoral immune response, with persistence till at least 12 months post-vaccination against most SARS-CoV-2 variants.