Reduced T cell and antibody responses to inactivated coronavirus vaccine among males and individuals above 55 years old

Abstract 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 Coronavac vaccinees above 55 years old could benefit from a heterologous third dose/booster vaccine to improve immune response and protection. Funding Brazilian Ministry for Science, Technology and Innovation, Sao Paulo State Foundation for Scientific research (FAPESP), JBS S.A.