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

Grunau B, O’Brien SF, Kirkham TL, Helmer J, Demers PA, Asamoah-Boaheng M, Drews SJ, Karim ME, Srigley JA, Sediqi S, O’Neill D, Drennan IR, Goldfarb DM. A Prospective Observational Cohort Comparison of SARS-CoV-2 Seroprevalence Between Paramedics and Matched Blood Donors in Canada During the COVID-19 Pandemic. Ann Emerg Med. 2022 Jul;80(1):38-45. doi: 10.1016/j.annemergmed.2022.03.009.

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

As part of the COVID-19 Occupational Risks, Seroprevalence and Immunity among Paramedics (CORSIP) study, CIFT-funded researchers Drs. Brian Grunau and David Goldfarb (University of British Columbia) did not find that, during the pre-Omicron waves, paramedics were at higher risk of catching SARS-CoV-2 than a control group of blood donors. There is evidence, however, that unvaccinated paramedics got COVID more frequently, compared to unvaccinated blood donors. Their findings are published in the Annals of Emergency Medicine. This project was undertaken in collaboration with Drs. Sheila O’Brien and Steven Drews of Canadian Blood Services.

Key Findings:

  • A comparison, which included samples from 1,713 paramedics and 19,515 blood donors found that seroprevalence was similar between paramedics (5%) and blood donors (4.1%)
  • Unvaccinated paramedics had three-fold higher seroprevalence compared to unvaccinated blood donors: 8% among unvaccinated paramedics and 3.5% among unvaccinated blood donors.

Blood samples were collected between January to July 2021, prior to the Omicron wave, from across Canada. The paramedic samples, drawn from British Columbia, Alberta, Saskatchewan, Manitoba, and Ontario, were compared to blood donor samples through a 1:1-matched designMatching is a technique used in studies to ensure that two groups being studied are comparable. In a 1:1 matched study, a case, affected by the variable of interest, is matched with one or more individuals not affected by the variable of interest. Cases are matched by ag, sex, location and other variables of interest. based on age (median of 38 years), sex (44% female), location, date of blood collection, and vaccination status and then by a greater overall comparison of the two groups. Researchers compared the seroprevalence looking at differences in risk and performed secondary analyses within subgroups defined by vaccination status.

Overall, paramedics demonstrated similar evidence of prior COVID-19 to that of blood donors. However, among unvaccinated individuals, the evidence of prior COVID-19 was significantly higher among paramedics. These results support the importance of vaccination among paramedics and other health care workers.