This is a summary, written by members of the CITF Secretariat, of:

Racine E, Boivin G, Longtin Y, McCormack D, Decaluwe H, Savard P, Cheng MP, Hamelin ME, Tadount F, Adams K, Bourdin B, Nantel S, Gilca V, Corbeil J, De Serres G, Quach C. The REinfection in COVID-19 Estimation of Risk (RECOVER) study: Reinfection and serology dynamics in a cohort of Canadian healthcare workers. medRxiv 2022.02.10.22269967; doi:

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

In a pre-print that has not yet been peer reviewed, CITF-funded researcher Dr. Caroline Quach-Thanh from the Université de Montréal and colleagues conducted a study among Canadian healthcare workers (HCWs) who had a previously documented SARS-CoV-2 infection to better understand vulnerability to reinfection. Over the course of 14 months, incidents of reinfection were rare (only 5 cases out of approximately 570 HCWs).  The cohort that was studied included those with mild, moderate, and severe infections in the first wave. Although antibodies waned in those infected (prior to vaccination), subjects who experienced more severe infections retained antibodies for a longer period of time.

Dr. Quach and her team sought to measure the incidence rate of reinfection and describe the duration of the immune response to the primary infection. Probable reinfection was defined as a positive PCR test 90 days or more after the first positive test.

Key Findings

  • Of 570 participants, the majority were female (83.0%) and Caucasian (79.3%). The median age was 42. Most worked in acute-care hospitals (54.1%) or in public long-term care facilities (24.4%). The most common reported profession was nurse/paramedic (40.4%), followed by patient care attendant (12.8%) and physician/medical resident (11.8%).
  • Five cases of probable reinfection were identified over 14 months of follow-up (August 17th 2020 and October 19th 2021).
  • Participants who reported symptomatic COVID-19 infection retained antibodies for a longer period of time (Median= for 420 days post-infection) than those who were asymptomatic (213 days). That has been shown elsewhere, the stronger your symptoms = the longer-lasting your antibody response.

The incidence of reinfection with SARS-CoV-2 among HCWs following a primary infection remained rare, but it’s important to note that this analysis was only in Montreal and predated the arrival of the Omicron variant.

This research is part of the on-going REinfection in COVID-19 Estimation of Risk (RECOVER) study.