Background Immune protection following either vaccination or infection with SARS-CoV-2 decreases over time.
Objective 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.
Methods Antibody titers were measured between January 31, 2021, and July 31, 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.
Higher SARS-CoV-2 IgG antibody titers were observed in vaccinated individuals after the second vaccination, than in convalescent individuals.
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.
Impact statement Large scale study display the kinetics of SARS-CoV-2 IgG antibodies present in individuals vaccinated with two doses of mRNA vaccine vs. unvaccinated patients who had recovered from the disease: initial levels of antibody are much higher in vaccinated patients, but decrease faster.
Introduction Immunity to severe acute respiratory syndrome coronavirus 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(Khoury et al.
While convalesced seropositive individuals have approximately 90% protection from SARS-CoV-2 reinfection, the effectiveness of vaccination has been reported as 50 - 95%(Kim et al.
There is a great concern regarding the weakened SARS-CoV-2 immune protection both in the vaccinated and convalescent populations(Wang et al.
More than five million Israelis have been fully vaccinated with two doses of the Pfizer-BioNTech vaccine as of May 26, 2021("Covid-19 dashboard," n.d.). However, in recent weeks, there has been a resurgence of SARS-CoV-2 cases in Israel.
Here, tracing one of these key factors, we describe the results of a large-scale study measuring the decrease rate of antibodies following administration of two doses of BNT162b2 vaccine, or SARS-CoV-2 infection in unvaccinated individuals in Israel.
https://www.medrxiv.org/content/10.1101/2021.08.19.21262111v1.full
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