1. Participants with fever >37.5 °C (axillary) or any acute disease at baseline (Day 1) or within the 3 days prior to randomization. Febrile participants with mild diseases may be enrolled at the investigator’s discretion. 2. Participants with a recent history of COVID-19 (= 4 weeks prior to visit 1), laboratory confirmed. 3. Participants with a history of serious vaccine-related adverse reaction or serious allergic reaction (e.g., anaphylaxis) to any study vaccine component, as described in the last summary of product characteristics for Sinovac/Butantan, AstraZeneca/Fiocruz or Pfizer/Wyeth. 4. Participants with a known bleeding disorder that, in the investigator’s opinion, would contraindicate intramuscular injection. 5. Participants with any progressive or serious neurological disorder, seizure disorder or history of Guillian-Barré syndrome. 6. Participants given treatment with immunosuppressant therapy within the last 90 days, including cytotoxic agents or systemic corticosteroids or planned receipt during the study period. If a short-term cycle of immunosuppressant systemic corticosteroid dose has been used to treat acute disease, the participant should not be enrolled in the study until corticosteroid therapy has been discontinued for at least 15 days prior to the first study vaccination. In case the participant has been on an immunosuppressant dose of a depot, intramuscular or intra-articular corticosteroid, 60 days should be waited for their enrolment in the study. Inhaled/nebulized, intra-articular, intrabursal or topical (skin or eyes) corticosteroids are allowed. 7. Participants with autoimmune diseases, other than: Hashimoto thyroiditis, vitiligo, psoriasis, discoid lupus and the like, HIV-positive participants and/or in treatment for HIV, 8. Participants given any other investigational product within the 30 days prior to Day 1 or who intend to take part in another clinical trial at any time during this study conduction. 9. Participants given any other licensed vaccine within 14 days prior to enrolment in this study or who plan to receive any vaccine up to 28 days after vaccination. 10. Participants given treatment with Rituximab or any other anti-CD20 monoclonal antibody within 9 months prior to Day 1 or planned during the study period. 11. Administration of intravenous immunoglobulins and/or any blood products within 3 months prior to enrolment or planned dosing during the study period. 12. Participants with any condition that, in the investigator’s opinion, could interfere with the status primary objectives or represent an additional risk for the participant. 13. Participants who have received any other vaccine for Covid-19 other than two Sinovac/Butantan doses.

1. Participants with fever >37.5 °C (axillary) or any acute disease at baseline (Day 1) or within the 3 days prior to randomization. Febrile participants with mild diseases may be enrolled at the investigator’s discretion. 2. Participants with a recent history of COVID-19 (= 4 weeks prior to visit 1), laboratory confirmed. 3. Participants with a history of serious vaccine-related adverse reaction or serious allergic reaction (e.g., anaphylaxis) to any study vaccine component, as described in the last summary of product characteristics for Sinovac/Butantan, AstraZeneca/Fiocruz or Pfizer/Wyeth. 4. Participants with a known bleeding disorder that, in the investigator’s opinion, would contraindicate intramuscular injection. 5. Participants with any progressive or serious neurological disorder, seizure disorder or history of Guillian-Barré syndrome. 6. Participants given treatment with immunosuppressant therapy within the last 90 days, including cytotoxic agents or systemic corticosteroids or planned receipt during the study period. If a short-term cycle of immunosuppressant systemic corticosteroid dose has been used to treat acute disease, the participant should not be enrolled in the study until corticosteroid therapy has been discontinued for at least 15 days prior to the first study vaccination. In case the participant has been on an immunosuppressant dose of a depot, intramuscular or intra-articular corticosteroid, 60 days should be waited for their enrolment in the study. Inhaled/nebulized, intra-articular, intrabursal or topical (skin or eyes) corticosteroids are allowed. 7. Participants with autoimmune diseases, other than: Hashimoto thyroiditis, vitiligo, psoriasis, discoid lupus and the like, HIV-positive participants and/or in treatment for HIV, 8. Participants given any other investigational product within the 30 days prior to Day 1 or who intend to take part in another clinical trial at any time during this study conduction. 9. Participants given any other licensed vaccine within 14 days prior to enrolment in this study or who plan to receive any vaccine up to 28 days after vaccination. 10. Participants given treatment with Rituximab or any other anti-CD20 monoclonal antibody within 9 months prior to Day 1 or planned during the study period. 11. Administration of intravenous immunoglobulins and/or any blood products within 3 months prior to enrolment or planned dosing during the study period. 12. Participants with any condition that, in the investigator’s opinion, could interfere with the status primary objectives or represent an additional risk for the participant. 13. Participants who have received any other vaccine for Covid-19 other than two Sinovac/Butantan doses.