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Abstract : In order to tackle COVID-19 pandemic and the emerging variants, researchers around the globe have investigated many vaccine candidates from different manufacturers, however vaccine development is not an easy task but is a top priority to restore normalcy as represented a step to achieve the desired herd immunity threshold. In this study we assessed and compared the level the peripheral mononuclear cells proliferation (PBMC) activity and in vitro INF-gamma release by the S1 spike protein stimulated T cells as they represent cellular immunity triggered from each vaccine against SARS-CoV2 infection in 123 vaccinated supposedly not infected subjects, by using Microculture tetrazolium assay (MTT) proliferation assay and an ELISA technique for the assessment of INF-gamma level in a cell culture supernatant. This study findings indicated that there was significant variety in the elicited levels of cell mediated immunity by dual vaccination at 1month and much more sustained different levels of cellular immunity among the studied previously mentioned vaccines by month8. Interestingly, both the PBMC proliferation percentage and the concentration of the in vitro IFN-y release, which represent the cellular immunity to SARS-CoV-2, were remarkably higher in 8 months than in 1month post-2nd dose vaccination groups of the three vaccines studied in this study (P<0.0001). For the PBMC proliferation percentage, AstraZeneca vaccine induced much higher proliferation percentage than Pfizer and Sinopharm (P<0.01) which both showed very close PBMC proliferation (P>0.05). For the concentration of the in vitro lFN-y release, again AstraZeneca induced distinguishing higher levels than Sinopharm and Pfizer groups (P<0.0001); nevertheless, unlike the trend found with the PBMC proliferation, Pfizer group showed significantly higher concentration of the in vitro lFN-y release than Sinopharm group (P<0.05). Moreover, the cellular immune response to all three vaccines studied showed no relationship with age, sex, and comorbidities of the vaccinated population of the study. Taken together, AstrZeneca showed superior effect on inducing robust cellular immunity followed by Pfizer vaccine, while Sinopharm showed minimal cellular immune response induction. And for all vaccines studied, the cellular immunity increased with time over 8 months after vsccination.