Long COVID risk and severity after COVID-19 infections and reinfections in Quebec healthcare workers

Importance: Long COVID, a chronic condition following SARS-CoV-2 infection, affects millions of people worldwide and can lead to significant functional impairment. Estimates of long COVID risk after a first COVID-19 infection vary, and data on risk following reinfections remain lacking. Objective: To estimate and compare long COVID risk and severity with first COVID-19 infection versus reinfections among healthcare workers (HCWs). Design: Retrospective cohort study based on an electronic survey among Quebec HCWs conducted between May 16 and June 15, 2023. A short telephone survey among randomly selected non-respondents further assessed potential response bias. Setting: Population-based study in Quebec, Canada. Participants: 397 222 HCWs were invited to participate in the electronic survey and 10 500 in the telephone survey. Main outcomes and measures: We defined long COVID cases as HCWs self-reporting COVID-19-attributed symptoms lasting ≥12 weeks, classified as mild, moderate, or severe based on perceived symptom intensity. We compared self-reported symptoms and functional limitations of cases to COVID controls (infected participants without long COVID) and non-COVID controls (uninfected participants). Risk and prevalence were estimated by number of infections, likely infecting variant and perceived acute COVID-19 severity. We conducted symptom clustering analyses using unsupervised learning techniques. Results: Estimated long COVID risk following any COVID-19 infection was similar among 22 496 online survey participants (17.0% [95%CI, 16.3%-17.6%] and 3 978 telephone survey participants (15.9% [14.6%-17.2%]. The cumulative risk increased with the number of infections, but reinfections were associated with three times lower risk of long COVID than first infections. Pre-Omicron infections and severe acute COVID-19 episodes correlated with higher long COVID risk and severity. Among prevalent long COVID cases, 43% were moderate and 33% severe. Compared to controls, dyspnea, neurocognitive symptoms, post-exertional malaise and smell/taste disturbances were most strongly associated with long COVID. Cluster analysis identified seven symptom groups with systemic, neurocognitive, pulmonary, and mood-related clusters being the most prevalent. Severe long COVID cases exhibited multiple symptom clusters and greater functional limitations. Conclusions: Long COVID is a common and disabling condition among HCWs. Societal and healthcare burden remains important and will continue to accrue given ongoing SARS-CoV-2 transmission and long COVID risk with reinfections.