Large-Scale Study of Antibody Titer Decay following BNT162b2 mRNA Vaccine or SARS-CoV-2 Infection.

Ariel Israel,Eli Magen,Shlomo Vinker,Yotam Shenhar,Ilan Green,Eytan Ruppin,Eugene Merzon,Alejandro A Schäffer,Avivit Golan-Cohen

doi:10.3390/vaccines10010064

Abstract

Immune protection following either vaccination or infection with SARS-CoV-2 is thought to decrease over time. We designed a retrospective study, conducted at Leumit Health Services in Israel, to determine the kinetics of SARS-CoV-2 IgG antibodies following administration of two doses of BNT162b2 vaccine, or SARS-CoV-2 infection in unvaccinated individuals. Antibody titers were measured between 31 January 2021, and 31 July 2021 in two mutually exclusive groups: (i) vaccinated individuals who received two doses of BNT162b2 vaccine and had no history of previous infection with COVID-19 and (ii) SARS-CoV-2 convalescents who had not received the vaccine. A total of 2653 individuals fully vaccinated by two doses of vaccine during the study period and 4361 convalescent patients were included. Higher SARS-CoV-2 IgG antibody titers were observed in vaccinated individuals (median 1581 AU/mL IQR [533.8–5644.6]) after the second vaccination than in convalescent individuals (median 355.3 AU/mL IQR [141.2–998.7]; p < 0.001). In vaccinated subjects, antibody titers decreased by up to 38% each subsequent month while in convalescents they decreased by less than 5% per month. Six months after BNT162b2 vaccination 16.1% subjects had antibody levels below the seropositivity threshold of <50 AU/mL, while only 10.8% of convalescent patients were below <50 AU/mL threshold after 9 months from SARS-CoV-2 infection. This study demonstrates individuals who received the Pfizer-BioNTech mRNA vaccine have different kinetics of antibody levels compared to patients who had been infected with the SARS-CoV-2 virus, with higher initial levels but a much faster exponential decrease in the first group.

Highlights

Immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been induced either through SARS-CoV-2 infection or vaccination and induces protection against reinfection or decreases the risk of clinically significant consequences [1]
Serology assays to quantify SARS-CoV-2 levels were performed for 2653 vaccinated individuals who never had a positive SARS-CoV-2 PCR test or serology test in the past, and 4361 patients recovering from SARS-CoV-2 and who had not been vaccinated at various times after the vaccination or infection
After BNT162b2 mRNA vaccination, we observed higher SARS-CoV-2 antibody titers in the convalescent individuals aged ≥60 years, while in the vaccinated population higher SARS-CoV-2 antibody titers were seen in younger patients

Summary

Introduction

Immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been induced either through SARS-CoV-2 infection or vaccination and induces protection against reinfection or decreases the risk of clinically significant consequences [1]. 90% protection from SARS-CoV-2 reinfection, the effectiveness of vaccination has been reported as 50–95% [2,3]. Both the memory B cell humoral response and spike-specific CD4+ cellular immune responses to SARS-CoV-2 diminish over time [4,5]. There is great concern regarding the weakened SARS-CoV-2 immune protection both in the vaccinated and convalescent populations [6]. More than five million Israelis (out of 9.3 million) were fully vaccinated with two doses of the Pfizer-BioNTech vaccine as of

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