Assessment of COVID-19 vaccine effectiveness among healthcare workers

Estonia is one of the countries participating in a prospective multi-country cohort study of hospital-based healthcare workers (HCW) to evaluate the effectiveness of COVID-19 vaccines in preventing laboratory-confirmed SARS-CoV-2 infection. The combination of data from multiple sites aims at providing sufficient statistical power to meet both the overarching primary objective and a range of more specific secondary objectives. This protocol has been adapted to the rapid vaccine roll-out for COVID-19 in many countries and accommodates the establishment of HCW cohorts subsequent to the implementation of vaccination programmes. All HCWs eligible to be vaccinated with COVID-19 vaccine can be enrolled in the study, including those who have already been vaccinated with a primary COVID-19 vaccination course, those that have received booster dose(s), those who intend or do not intend to be vaccinated and those who are not sure. At enrolment, study participants complete a baseline enrolment survey about demographics, clinical comorbidities, and work- and community-related behaviours related to infection risk. In addition, a serology samples and a respiratory specimens will be collected from participants.