Persistence of neutralizing antibodies a year after SARS-CoV-2 infection in humans.

Haveri, Anu; Ekström, Nina; Solastie, Anna; Virta, Camilla; Österlund, Pamela; Isosaari, Elina; Nohynek, Hanna; Palmu, Arto A; Melin, Merit

Most subjects develop antibodies to SARS-CoV-2 following infection. In order to estimate the duration of immunity induced by SARS-CoV-2 it is important to understand for how long antibodies persist after infection in humans. Here, we assessed the persistence of serum antibodies following wild-type SARS-CoV-2 infection at 8 and 13 months after diagnosis in 367 individuals. The SARS-CoV-2 spike immunoglobulin G (S-IgG) and nucleoprotein IgG (N-IgG) concentrations and the proportion of subjects with neutralizing antibodies (NAb) were assessed. Moreover, the NAb titers among a smaller subset of participants (n = 78) against a wild-type virus (B) and variants of concern (VOCs): Alpha (B.1.1.7), Beta (B.1.351) and Delta (B.1.617.2) were determined. We found that NAb against the wild-type virus persisted in 89% and S-IgG in 97% of subjects for at least 13 months after infection. Only 36% had N-IgG by 13 months. The mean S-IgG concentrations declined from 8 to 13 months by less than one third; N-IgG concentrations declined by two thirds. Subjects with severe infection had markedly higher IgG and NAb levels and are expected to remain seropositive for longer. Significantly lower NAb titers against the variants compared to the wild-type virus, especially after a mild disease, suggests reduced protection against VOCs. This article is protected by copyright. All rights reserved.