This is a quasi-experimental 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.

Inclusion Criteria:

• Age between 18 and 49 years
• Demonstrate availability to be accompanied during the follow-up time defined in the study, through visits, telephone contacts, or other means of digital communication.

Exclusion Criteria:

• Prior vaccination for COVID-19;
• Diagnosis of COVID-19 in the last 28 days (nasal and oropharyngeal swab);
• History of severe allergic reaction or anaphylaxis to study vaccine components;
• Report of fever in the 72 hours prior to vaccination (the inclusion may be postponed until the participant completes 72 hours without fever);
• Possible or confirmed of COVID-19 on the day of vaccination (in this situation, vaccination can be postponed until the participant completes 72 hours without symptoms or the diagnosis is ruled out);
• Have received live attenuated virus vaccine in the last 28 days or inactivated vaccine in the last 14 days prior to inclusion in the study, or have immunization scheduled for the first 28 days after their inclusion in the study;
• Any other condition that, in the opinion of the principal investigator or his medical representative, could endanger the safety or rights of a potential participant or that would prevent him or her from complying with this protocol;
• Pregnancy or breastfeeding.