This is a quasi-experimental Phase 4 study with risk-based allocation. Public security and education professionals from the state government will be included.

In the initial evaluation, the presence of comorbidities associated with an increased risk of serious disease due to COVID-19 will be evaluated, according to the national plan for the implementation of vaccination against COVID-19.

Those with at least one of these comorbidities will be invited to receive the study vaccine in two doses, with an interval of 28 days (±7 days). Participants with low risk (without comorbidities as a risk factor for severe COVID-19 according to the national plan for the implementation of vaccination against COVID-19) will not receive the vaccine within the scope of the research project. If, after 12 months, the participant in the low-risk group (no vaccine) has not received CoronaVac, or any other vaccine available, he/she will receive the vaccine, exactly as offered in the other group (two doses of CoronaVac with an interval of 28 days - with a tolerance of 7 days before or after).

All participants will be followed up for 12 months from inclusion in the study. Immunization is expected to reduce the risk of moderate to severe disease of those with comorbidities to the level of those of the same age group who do not have these comorbidities but face similar occupational risks.