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 …

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection has brought
new challenges to the global prevention and control of coronavirus disease 2019 (COVID …

The duration of protection of the third (booster) dose of the BioNTech/Pfizer BNT162b2
mRNA Coronavirus Disease 2019 vaccine has been the subject of recent investigations, as …

Background There is a paucity of data on vaccine-induced or infection-induced (hybrid or
natural) immunity against omicron (B. 1.1. 529) subvariant BA. 2, particularly in comparing …

T cells are critical for immune protection against severe COVID-19, but it has remained
unclear whether repeated exposure to SARS-CoV-2 antigens delivered in the context of …

Importance The Omicron variant is phylogenetically and antigenically distinct from earlier
SARS-CoV-2 variants and the original vaccine strain. Protection conferred by prior SARS …

Importance Observational (nonexperimental) studies that aim to emulate a randomized trial
(ie, the target trial) are increasingly informing medical and policy decision-making, but it is …

Durable humoral immunity is mediated by long-lived plasma cells (LLPCs) that reside in the
bone marrow. It remains unclear whether severe acute respiratory syndrome coronavirus 2 …

Background Individuals with a prior Severe Acute Respiratory Syndrome Coronavirus 2
(SARS-CoV-2) infection have a moderate to high degree of protection against reinfection …

The objective of this study was to investigate the incidence and risk factors associated with
COVID-19 vaccine breakthrough infections. We included all persons≥ 18 years that had …