Elsevier

Virology

Volume 578, January 2023, Pages 111-116
Virology

Brief Communication
Long-term persistence of IgG antibodies in recovered COVID-19 individuals at 18 months post-infection and the impact of two-dose BNT162b2 (Pfizer-BioNTech) mRNA vaccination on the antibody response: Analysis using fixed-effects linear regression model

https://doi.org/10.1016/j.virol.2022.12.003Get rights and content
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Highlights

  • This is the longest observation (March 2020–September 2021) for the presence of antibodies against SARS-CoV-2 in recovered individuals along with the impact of 2 dose-BNT162b2 vaccination on the titers. Fixed-effect regression models were used for statistical analysis which could be also used to predict future titer trends. At 18 months, 97% of participants tested positive for anti-NCP hinting towards the persistence of infection-induced immunity even for the vaccinated individuals. Our study findings demonstrate that while double dose vaccination boosted the IgG titers in recovered individuals 161 times, this “boost” was relatively short-lived.

  • The unvaccinated recovered individuals, in contrast, continued to show a steady decline but detectable antibody levels.

  • The major strengths of our study include the longest observation (March 2020–September 2021) for the presence of antibodies against SARS-CoV-2 in recovered individuals along with the impact of 2 dose-BNT162b2 vaccination on the titers. Secondly, fixed-effect regression models were used for statistical analysis that diminishes the impact of confounding by (unmeasured) fixed/time-invariant factors. These modeling results could also be used to predict future titer trends. Thirdly, since the immunoassay to detect anti-NCP was reintroduced at 18 months, even the vaccinated individuals could be analyzed for the persistence of infection-induced immunity not generated by mRNA spike-based vaccination.

Abstract

This era of emerging variants needs a thorough evaluation of data on the long-term efficacy of immune responses in vaccinated as well as recovered individuals, to understand the overall evolution of the pandemic. In this study, we aimed to assess the dynamics of IgG response over 18 months in n = 36 patients from the Umbria region in Italy, who had a documented history of COVID-19 infection in March 2020, and then compared the impact of two-dose BNT162b2 (Pfizer-BioNTech) vaccination on the antibody responses of these patients with the ones who did not receive any dose of vaccine. This is the longest observation (March 2020–September 2021) for the presence of antibodies against SARS-CoV-2 in recovered individuals along with the impact of 2 dose-BNT162b2 vaccination on these responses. Fixed-effect regression models were used for statistical analysis which could be also used to predict future titer trends. At 18 months, 97% participants tested positive for anti-NCP hinting towards the persistence of infection-induced immunity even for the vaccinated individuals. Our study findings demonstrate that while double dose vaccination boosted the IgG levels in recovered individuals 161 times, this “boost” was relatively short-lived. The unvaccinated recovered individuals, in contrast, continued to show a steady decline but detectable antibody levels. Further studies are required to re-evaluate the timing and dose regimen of vaccines for an adequate immune response in recovered individuals.

Data availability

Data will be made available on request.

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