Inclusion Criteria:  Signed informed consent Previously totally immunized, I.e., two doses for Corona Vac (Sinovac) or ChAdOx1 (AZ 1222, Astra Zeneca, and one dose for Ad26.Co2.S (Janssen) vaccines at least three months before enrollment Negative RT-PCR for SARS-CoV-2 at the moment of triage No previous history of laboratory confirmed Covid-19  Exclusion Criteria:  Pregnancy Participation in other vaccine trial Active decompensated chronic condition, namely, cardiovascular, respiratory, neurological, metabolic or hepatic diseases Any immunocompromise condition (primary immunodeficiencies, auto-immune diseases, long-term use of corticosteroids, solid organ transplant recipients, hematopoietic stem-cell transplant recipients, human-immunodeficiency virus active infection) Active cancer Hepatitis B or C History of allergic reactions to any vaccine component, including excipients and preservatives (neomycin, streptomycin, polymyxin B, eggs Blood donation in the past 4 weeks before screening Received blood product in the past 3 months before screening