(A) CD4+ cell ratio at baseline, 1?month, and 3?months after boosters. T cell ratios were determined by flow cytometry. The Trifloxystrobin intracellular IFN\ and IL\2 responses were measured by ELISpot assay. Results We found a 3.38\fold increase in neutralizing antibody geometric mean titers (NA GMT, 78.69) 1?month after BNT booster and maintained at the third month (NA GMT, 80). Nevertheless, in the CV booster group, significantly lower NA GMT than BNT after 1?month and 3?months were observed (21.44 and 28.44, respectively) ( em p /em ? ?.001). In the ELISpot assay, IL\2?levels after BNT were higher than baseline and CV booster ( em p /em ? ?.001) while IFN\ levels were significantly higher than baseline ( em p /em ? ?.001). The CD8+CD38+CD69+ and CD4+CD38+CD69+ T cells were stimulated predominantly in the third month of the BNT boosters. Conclusion The neutralizing antibody levels after 3?months of the BNT booster were higher than the antibody levels after CV in fully vaccinated individuals. On the contrary, ratio of the effector T cells increased along with greater IFN\ activation after BNT booster. By considering the waning immunity, we suggest a new booster dose with BNT for the countries that already had two doses of primary CV regimens. strong class=”kwd-title” Keywords: SARS\CoV, T cells, vaccines Abstract This study determines the effects of BNT162b2 (BNT) and CoronaVac (CV) boosters on the humoral and cellular immunity of individuals who had two doses of CV vaccination. The neutralizing antibody levels after 3?months of the Trifloxystrobin BNT booster are higher Trifloxystrobin than the antibody levels after CV in fully vaccinated individuals. The ratio of the effector T cells increases along with greater IFN\ activation after BNT booster. AbbreviationsGMTgeometric mean titerPBMCsperipheral blood mononuclear cellsPRNT50plaque reduction neutralization testSFUspot forming units 1.?INTRODUCTION The worldwide use of effective and safe COVID\19 vaccines is still a high priority to control the pandemic and to reduce the burden of COVID\19. The vaccine type and vaccination schedule affect many of the cellular and molecular elements of innate and adaptive immune systems. Estimation of the immune responses after SARS\CoV\2 vaccinations is one of the important parameters in order to predict the efficacy of booster vaccines. Therefore, testing the effectiveness of COVID\19 vaccines in different vaccination schedules is necessary as there are a variety of vaccine availabilities, worldwide. Following primary vaccination, antibody and T\cell responses have decreased over time. 1 A booster dose being administered 6?months after the second dose of various vaccines significantly increased neutralizing antibody concentrations. 2 The heterologous vaccine regimens were reported to stimulate neutralizing antibodies more than the homologous vaccine protocols. 3 In Turkey, the inactivated vaccine CoronaVac (Sinovac Life Sciences) was the first vaccine to receive approval by the Ministry of Health. Healthcare workers and individuals over the age of 65 were suggested two doses of CV administered 2? months apart in the initial phase of the vaccination program. 4 After 6?months, the Ministry of Health of Turkey recommended a booster of BNT as an alternative option to the CV booster. In early studies of the CV, effectiveness after two\dose schedules was reported as 60%C90%. 4 , 5 Nevertheless, these studies were performed approximately 6?weeks after the second dose. Six months after the second dose of CV, neutralizing antibody titers declined below the seropositivity cut\off value while a remarkable increase in the neutralizing antibody concentrations was observed with the administration of a third dose. 6 However, our knowledge on the humoral and cellular immune responses obtained by BNT and CV boosters following two doses of primary CoronVac vaccination is still limited. Rabbit Polyclonal to ZC3H11A In this study, we aimed to explore the neutralizing antibody and T\cell responses after the booster doses of CV and BNT following two doses of CV. 2.?MATERIALS AND METHODS 2.1. Study design and participants The study was conducted in three centers (Ko? University Hospital, Istanbul School Cerrahpasa Medical center, and Istanbul School, Istanbul Medical College Medical center) in Istanbul, Turkey. People who was simply immunized with two dosages of CV previously, no former background of COVID\19 had been.