Coronavac is an inactivated SARS-CoV-2 vaccine that has been rolled out in several low and middle-income countries including Brazil. We aimed to assess the T cell and antibody responses of vaccinees as compared to convalescent subjects.
Background. CoronaVac is an inactivated SARS-CoV-2 vaccine that has been rolled out in several low and middle-income countries including Brazil, where it was the mainstay of the first wave of immunization of health care workers and the elderly population. We aimed to assess the T cell and antibody responses of vaccinees as compared to convalescent subjects. Methods. We detected IgG against SARS-CoV-2 antigens, neutralizing antibodies against the original SARS-CoV-2 strain, and used SARS-CoV-2 peptides to detect IFN-g and IL-2 specific T cell responses in a cohort of CoronaVac vaccinees ( N=101) and convalescent ( N=72) individuals. Findings. Among vaccinees, 95% displayed T cell or antibody responses to SARS-CoV-2 as compared to 99% convalescent individuals. However, we observed that among vaccinees, males and individuals 55 years or older developed significantly lower anti-RBD, anti-NP and neutralizing antibody responses as well as antigen-induced IL-2 production by T cells. Interpretation. Even though some studies indicated Coronavac helped reduce mortality among elderly people, considering the current dominance of the gamma variant of concern (VOC) and potential increase of the delta VOC, in Brazil, our data support that Coronavac vaccinees above 55 years old are likely to benefit from a third dose to boost immune response and protection. Funding: Brazilian Ministry for Science, Technology and Innovation, Sao Paulo State Foundation for Scientific research (FAPESP), JBS S.A.