Introduction During the first lockdown in Spain (March-June, 2020) essential workers may have been at increased risk of coronavirus disease 2019 (COVID-19) via occupational exposure. Results from published studies are heterogeneous.

Methods Ongoing population-based cohort studies from Catalonia were pooled to form the COVICAT study. A random sub-population donated a blood sample (May-July, 2020) for validated multiplex serology testing. Occupational analyses were restricted to working age (18–65 years). Participants responded to a web-based or telephone survey including questions on socio-demographics, pre-pandemic health, behavioural and environmental risk factors. Occupational questions covered mode of work (e.g. telework), job title, availability of personal protective equipment (PPE), and mode of commuting. Job titles were coded by an occupational hygienist to the Spanish CNO-11 and cross-walked to ISCO-08. COVID-19 cases were defined by symptoms or hospitalisation and SARS CoV-2 seropositivity based on immune responses to 15 isotype-antigen combinations (serology sub-cohort). Logistic regression models were built for type of work, job titles and job-exposure matrix (JEM), covering several dimensions and levels of SARS-CoV-2 transmission probabilities , and adjusted for age, sex, education, deprivation index, population density and survey type.

Results This analysis included 8,582 participants, of which 3,599 were tested for SARS-CoV-2 antibodies, median (SD) age 53.7 (6.3) years, 59.9% were women. The relative risk for COVID-19 for work in the usual workplace compared to telework was 1.87 (95% CI: 1.44, 2.42), and 1.44 (95% CI: 1.09, 1.90) among the serology study. The relative risk for nurses who worked in their usual workplace was 4.57 (95% CI: 3.12, 6.7). Detailed results by job title, JEM, availability of PPE and commuting mode will be presented.

Conclusions This study has several strengths, including random serology testing and individual-level exposure data. Detailed results may support extended legal definitions of COVID-19 as a recognized occupational disease.