To describe the safety and reactogenicity profile of a fractional doses of AstraZeneca/Fiocruz or a fractional dose of Pfizer/Wyeth vaccines or a full dose of AstraZeneca/Fiocruz vaccine given as single additional dose in participants previously vaccinated with two Sinovac/Butantan doses.;To assess the immune response measured as binding antibodies (IgG ELISA) following vaccination with a fractional dose of AstraZeneca/Fiocruz or a fractional dose of Pfizer/Wyeth vaccine or a full dose of AstraZeneca/Fiocruz vaccine given as single additional dose in Adults (= 18 years) previously vaccinated with Sinovac/Butantan doses.

To describe the safety and reactogenicity profile of a fractional doses of AstraZeneca/Fiocruz or a fractional dose of Pfizer/Wyeth vaccines or a full dose of AstraZeneca/Fiocruz vaccine given as single additional dose in participants previously vaccinated with two Sinovac/Butantan doses.;To assess the immune response measured as binding antibodies (IgG ELISA) following vaccination with a fractional dose of AstraZeneca/Fiocruz or a fractional dose of Pfizer/Wyeth vaccine or a full dose of AstraZeneca/Fiocruz vaccine given as single additional dose in Adults (= 18 years) previously vaccinated with Sinovac/Butantan doses.