Quantifying the risk of SARS‐CoV‐2 reinfection over time

Abstract

Summary Despite over 140 million SARS‐CoV‐2 infections worldwide since the beginning of the pandemic, relatively few confirmed cases of SARS‐CoV‐2 reinfection have been reported. While immunity from SARS‐CoV‐2 infection is probable, at least in the short term, few studies have quantified the reinfection risk. To our knowledge, this is the first systematic review to synthesise the evidence on the risk of SARS‐CoV‐2 reinfection over time. A standardised protocol was employed, based on Cochrane methodology. Electronic databases and preprint servers were searched from 1 January 2020 to 19 February 2021. Eleven large cohort studies were identified that estimated the risk of SARS‐CoV‐2 reinfection over time, including three that enrolled healthcare workers and two that enrolled residents and staff of elderly care homes. Across studies, the total number of PCR‐positive or antibody‐positive participants at baseline was 615,777, and the maximum duration of follow‐up was more than 10 months in three studies. Reinfection was an uncommon event (absolute rate 0%–1.1%), with no study reporting an increase in the risk of reinfection over time. Only one study estimated the population‐level risk of reinfection based on whole genome sequencing in a subset of patients; the estimated risk was low (0.1% [95% CI: 0.08–0.11%]) with no evidence of waning immunity for up to 7 months following primary infection. These data suggest that naturally acquired SARS‐CoV‐2 immunity does not wane for at least 10 months post‐infection. However, the applicability of these studies to new variants or to vaccine‐induced immunity remains uncertain.

SARS-CoV-2 reinfections: Overview of efficacy and duration of natural and hybrid immunity

“…health care workers) or with other study designs (e.g. solely based on antibodies with thus unclear infection date or missing control groups) that are all in line with the notion that natural immunity significantly protects against reinfections ( Abrokwa et al, 2021 ; Fabianova et al, 2021 ; Hall et al, 2021 ; Hanrath et al, 2021 ; Harvey et al, 2021 ; Iversen et al, 2021 ; Jeffery-Smith et al, 2021 ; Kojima et al, 2021 ; Leidi et al, 2021 ; Letizia et al, 2021 ; O Murchu et al, 2021 ; Rennert and McMahan, 2021 ).…”

Robust and Persistent B- and T-Cell Responses after COVID-19 in Immunocompetent and Solid Organ Transplant Recipient Patients

“…In conclusion, despite immunosuppressive therapy, TX patients developed a robust immune response after SARS-CoV-2 infection, comparable to that observed in IC patients. The immune response persists until one year after SARS-CoV-2 infection, and it is likely that the immunological memory could persist for a long time and may protect both the IC and TX populations from SARS-CoV-2 secondary infections [34,35]. Future evaluation of the magnitude and persistence of the immune response elicited by SARS-CoV-2 vaccines in transplant recipients would provide essential information about immune protection from COVID-19 that could be achieved in this fragile population.…”

The Emergence of Omicron: Challenging Times Are Here Again!

“…One of the salient features of omicron is its ability to cause reinfection. Studies before the emergence of omicron showed 0.1%-1% risk of reinfection and prior infection with SARS-CoV-2 to give more than 80% protection against reinfection [26]. Linear data analysis from South Africa showed that while reinfection rates did not go up during the beta and delta waves, they went up significantly during the omicron wave; the hazard ratio for reinfection vs. primary infection between 1st and 27th November was 2.39 as compared to wave 1 [18].…”