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

Racine É, Boivin G, Longtin Y, Mccormack D, Decaluwe H, Savard P, Cheng MP, Hamelin ME, Carbonneau J, Tadount F, Adams K, Bourdin B, Nantel S, Gilca V, Corbeil J, De Serres G, Quach-Thanh C. The REinfection in COVID‐19 Estimation of Risk (RECOVER) study: Reinfection and serology dynamics in a cohort of Canadian healthcare workers. Influenza Other Respir Viruses; 2022; 1-10. doi:

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

In a paper published in Influenza and Other Respiratory Viruses, CITF-funded researcher Dr. Caroline Quach-Thanh from the Université de Montréal and other members of the REinfection in COVID‐19 Estimation of Risk (RECOVER) project, studied 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 6 cases out of approximately 569 HCWs).  

Key Findings

  • Participants who reported symptomatic COVID-19 infection retained antibodies for a longer period of time (Median= for 415 days post-infection) than those who were asymptomatic (213 days). This has been shown elsewhere: the stronger the symptoms, the longer-lasting the antibody response.
  • The incidence of reinfection with SARS-CoV-2 among HCWs following a primary infection remained rare over the first year after primary infection, but it’s important to note that this analysis was only in Montreal and predated the arrival of the Omicron variant.

The cohort that was studied included those with mild, moderate, and severe infections in the first wave. Probable reinfection was defined as a positive PCR test 90 days or more after the first positive test. Although antibodies waned in those infected (prior to vaccination), subjects who experienced more severe infections retained antibodies for a longer period of time.

Of the participants, the majority were female (83.0%) and Caucasian (79.3%). The median age was 42. Most worked in hospitals (54.1%) or in public long-term care facilities (24.4%). The most common reported profession was nurse/paramedic (40.2%), followed by patient care attendant (12.8%) and physician/medical resident (11.8%). Five cases of probable infection and one confirmed reinfection were identified between August 21st, 2020 and March 1, 2022.