Long COVID risk and severity after COVID-19 infections and reinfections: a retrospective cohort study among healthcare workers

We evaluated long COVID risk, prevalence and severity in a population-based cohort of Quebec healthcare workers (HCWs), in Canada, and the effect of reinfections, variants, and acute infection's severity. Retrospective survey-based cohort study conducted in Spring 2023. HCWs self-reporting COVID-19-attributed symptoms lasting ≥12 weeks were long COVID cases, classified as mild, moderate, or severe based on self-perceived symptom intensity and compared to controls. We estimated long COVID prevalence and cumulative incidence by number of infections, and following first and subsequent infections stratified by infecting variant and acute COVID-19 severity. Adjusted risk ratios were computed using robust Poisson models. 22 496 (of 397 222 invited HCWs) and 3 978 (of 10 500) participated in the electronic and telephone surveys. Long COVID cumulative risk among infected participants was 17.0% (95%CI:16.3%-17.6%), increasing with number of infections. Estimated prevalence was 5.6% (95%CI:4.9%-6.3%). Reinfections (vs. first infection), Omicron (vs. ancestral variant) and non-severe acute infection (vs. severe) were associated, respectively, with 40%, 34% and 72% lower long COVID risk. Severe cases exhibited multiple symptoms and substantial functional limitations. Long COVID is a common and disabling condition. With the ongoing SARS-CoV-2 transmission, interventions targeting the frequency and severity of reinfections may reduce future long COVID burden.