Neutralizing Antibody Activity to SARS-CoV-2 Delta (B.1.617.2) and Omicron (B.1.1.529) After One and Two Doses of BNT162b2 Vaccine in Infection-Naïve and Previously-Infected Individuals

By James N Moy, MD, Mark Anderson, PhD, Xiaoying Shen, DVM, PhD, Jia Fu, MS, Michael Stec, MS, Amy Gosha, BSN, Dina Naquiallah, MD, Jennifer Kinslow, PhD, David C Montefiori, PhD, Gavin Cloherty, PhD, Alan Landay, PhD

Abstract

Previous reports demonstrated that SARS-CoV-2 binding IgG did not increase significantly between first and second doses of the BNT162b2 vaccine in previously-infected individuals. We tested neutralizing antibodies (nAb) against SARS-CoV-2 Delta and Omicron variants post first and second doses of BNT162b2 in infection-naïve and previously-infected individuals. Delta, but not Omicron, nAb significantly increased from first to second dose in both groups of individuals. Importantly, we found Omicron nAb titers were much lower than Delta nAb titers and that even after two doses of vaccine, 17 of 29 individuals in the infection-naïve group and 2 of 27 individuals in the previously-infected group did not have detectable Omicron nAb titers. Infection history alone did not adequately predict if a second dose resulted in adequate nAb. For future variants of concern, the discussion on the optimal number of vaccine doses should be based on studies testing for nAb against the specific variant.

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