Incidence and risk factors of COVID-19 infection in healthcare workers at a tertiary referral centre: from the first to the sixth wave of the pandemic

OBJECTIVES: The aim of the study was to determine the incidence of COVID-19 infection among healthcare workers (HCWs) at Reina Sofia University Hospital (RSUH) in Cordoba, Spain, from the first to the sixth wave of the pandemic. Additionally, we analysed the characteristics of infections across different age groups, genders, professional categories, hospital services, and COVID-19 vaccination status. METHODS: An observational, longitudinal, analytical, and retrospective study was conducted, considering characteristics of person, time, HCWs category, and diagnostic test. The results of the tests of RSUH HCWs between March 2020 and March 2022 were analysed. Socio-demographic and clinical data were collected from the Alert Network of the Epidemiological Surveillance System of Andalusia. RESULTS: The study included 6,794 HCWs, of whom 1,513 (22.3%) tested positive for COVID-19. The distribution of COVID-19 cases among HCWs across the six waves was as follows: first wave - 150 cases (9.9%), second wave - 597 cases (39.4%), third wave - 225 cases (14.9%), fourth wave - 24 cases (1.6%), fifth wave - 121 cases (8%), and sixth wave - 396 cases (26.2%). The mean age of confirmed cases was 46.32 years (SD = 11.53), with a lower infection risk among HCWs aged 61-70 years. Only 16.9% of cases had received two vaccine doses at the time of infection. Nursing was the most affected professional category (30%). CONCLUSIONS: COVID-19 infection risk varies by age and HCWs category, decreasing in older HCWs but increasing among residents and certain specialties. During the Omicron variant's dominance, vaccines seemed less effective in reducing transmission. Health education programmes for both patients and HCWs are necessary to limit the spread of the disease.