An Effectiveness Study of the Sinovac's Adsorbed COVID-19 (Inactivated) Vaccine

This is a stepped-wedge cluster randomized trial to assess effectiveness of Sinovac's Adsorbed COVID-19 (Inactivated) vaccine. Residents in the urban area of a municipality are eligible to participate. The city was divided in clusters and those cluster were grouped to determine the offer of vaccination in four steps. The vaccine will be offered to adults (18 years old and above) according to the location of their homes in a cluster. The vaccine schedule is two doses with four-weeks interval. Baseline samples to determine previous immunity will be collected before vaccination. Cases of COVID-19 reported in the city will be recorded according to the WHO clinical progression scale. Comparison of periods before and after vaccination and relation to immunization coverage will be considered for the assessment of effectiveness in the clusters and groups of clusters.