Intervention: Oxford/AstraZeneca - 0.5 mL single dose, intramuscular in deltoid, with an interval of 180 days (+/- 30 days) from the 2nd dose of the initial vaccination schedule with CoronaVac~Inclusion criteria:~Have voluntarily participated and be in regular follow-up monitoring by the COVACMANAUS study;~Have completed the vaccination schedule with 2 doses of CoronaVac, as per the COVACMANAUS study protocol for at least 180 days (+/- 30 days);~Demonstrate availability to be followed during the follow-up period defined in the study, through visits, telephone contacts or other digital means of communication;~Accept to participate in this new study for 6 (six) months.~Exclusion criteria~Confirmed diagnosis of COVID-19 within the last 28 days (antigen test or RT-PCR). In this situation, vaccination can be postponed until the participant completes 30 days;~Report of fever within 72 hours prior to vaccination (inclusion can be postponed until the participant completes 72 hours without fever and COVID-19 is discarded);~Having received live attenuated virus vaccine in the last 28 days or inactivated vaccine in the last 14 days prior to inclusion in the study;~Any other condition that, in the opinion of the Principal Investigator or its medical representative, could jeopardize the safety or rights of a potential participant or prevent them from complying with this protocol;~Pregnancy or lactation.~Type of study/study design: Experimental, single-arm study in participants with comorbidities, previously immunized with 2 doses of CoronaVac, who will receive a booster vaccine with 1 dose of the Oxford/AstraZeneca vaccine.~Sample size: all active participants from the COVACManaus study (up to 5071)~Primary outcome: Detection and titration of antibodies against SARS-CoV-2 before (D0), at D90 and D180 after booster vaccination~Secondary outcomes:~Profile of the cell-mediated immune response in a subgroup of participants, before (D0), at D90 and D180 after booster vaccination;~Ability to neutralize antibodies in a subgroup of participants before (D0), in D90 and D180 after the vaccine booster;~Memory cell populations in a subgroup of participants before (D0), in D90 and D180 after booster vaccination.~Detection and titration of antibodies against SARS-CoV-2 and its association with the history of physical activity or sedentary lifestyle.
Experimental, single-arm study in participants with comorbidities, previously immunized with 2 doses of CoronaVac, who will receive a booster vaccine with 1 dose of the Oxford/AstraZeneca vaccine.