A Prospective Observational Cohort Comparison of SARS-CoV-2 Seroprevalence Between Paramedics and Matched Blood Donors in Canada During the COVID-19 Pandemic

• Published in: Annals of emergency medicine 2022-07, Vol.80 (1), p.38-45
• Main Authors: Grunau, Brian, MD, MHSc, O’Brien, Sheila F., PhD, Kirkham, Tracy L., PhD, Helmer, Jennie, ACP, MEd, Demers, Paul A., PhD, Asamoah-Boaheng, Michael, MPhil, Drews, Steven J., PhD, Karim, Mohammad Ehsanul, PhD, Srigley, Jocelyn A., MD, MSc, Sediqi, Sadaf, BSc, O’Neill, David, PhD, Drennan, Ian R., ACP, PhD, Goldfarb, David M., MD
• Format: Article
• Language: English
• Subjects: Allied Health Personnel; Blood Donors; Cohort Studies; COVID-19 - epidemiology; Emergency; Emergency Medical Services/Original Research; Female; Humans; Male; Pandemics; Prospective Studies; SARS-CoV-2; Seroepidemiologic Studies
• ISSN: 0196-0644; 1097-6760
• DOI: 10.1016/j.annemergmed.2022.03.009

Study objectiveSARS-CoV-2 represents an occupational risk to paramedics, who work in uncontrolled environments. We sought to identify the occupation-specific risk to paramedics by comparing their seroprevalence of SARS-CoV-2 infection-specific antibodies to that of blood donors in Canada. MethodsIn this prospective cohort study, we performed serology testing (Elecsys Anti-SARS-CoV-2 nucleocapsid assay) on samples from paramedics and blood donors (January to July 2021) in Canada. Paramedic samples were compared to blood donor samples through 1:1-matched (based on age, sex, location, date of blood collection, and vaccination status) and raking weighted comparisons. We compared the seroprevalence with a risk difference (and 95% confidence interval [CI]) and performed secondary analyses within subgroups defined by vaccination status. ResultsThe 1:1 match included 1,627 cases per group; in both groups, 723 (44%) were women, with a median age of 38. The raking weighted comparison included 1,713 paramedic samples and 19,515 blood donor samples, with similar characteristics. In the 1:1 match, the seroprevalence was similar (difference 1.2; 95% CI –0.20 to 2.7) between paramedics (5.2%) and blood donors (3.9%). The raking weighted comparison was consistent (difference 0.97; 95% CI –0.10 to 2.0). The unvaccinated paramedic samples, in comparison to the blood donor samples, demonstrated a higher seroprevalence in the 1:1 (difference 5.9; 95% CI 1.8 to 10) and weighted (difference 6.5; 95% CI 1.8 to 10) comparisons. Among vaccinated cases, the between-group seroprevalence was similar. ConclusionOverall, paramedics demonstrated similar evidence of prior SARS-CoV-2 infection to that of blood donors. However, among unvaccinated individuals, evidence of prior infection was higher among paramedics compared to blood donors.