Seroprevalence surveys suggest that more than a third and possibly more than half of the
global population has been infected with SARS-CoV-2 by early 2022. As large numbers of …

Introduction A precise estimate of the frequency and severity of SARS‐CoV‐2 reinfections
would be critical to optimize restriction and vaccination policies for the hundreds of millions …

Booster vaccination with messenger RNA (mRNA) vaccines has been offered to adults in
England starting on 14 September 2021. We used a test-negative case–control design to …

Background Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
provides natural immunity against reinfection. Recent studies have shown waning of the …

Background Waning of vaccine protection against coronavirus disease 2019 (Covid-19) and
the emergence of the omicron (or B. 1.1. 529) variant of the severe acute respiratory …

Background Real-world evidence supporting vaccination against COVID-19 in individuals
who have recovered from a previous SARS-CoV-2 infection is sparse. We aimed to …

Omicron subvariants continuingly challenge current vaccination strategies. Here, we
demonstrate nearly complete escape of the XBB. 1.5, CH. 1.1, and CA. 3.1 variants from …

Background The duration and effectiveness of immunity from infection with and vaccination
against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are relevant to …

Immunity against Omicron Variants after Vaccine Boost After a third (booster) dose of SARS-
CoV-2 vaccine, immunity waned more slowly than after two doses and even more slowly in …

Waning SARS-CoV-2 Immunity in Qatar The protection afforded by the mRNA-1273 vaccine
against SARS-CoV-2 infection in Qatar seemed to wane over several months after …