Abstract
Background: Being a long-term preventive measure, COVID-19 vaccines are used in global populations. In India, country-wide immunization drive was initiated in January 2021.Methods: To assess immune response of health-care-workers to COVISHIELD(n=187) and COVAXIN(n=21), blood samples collected pre-vaccination and 1month-post-1/post-2 dose, administered 28days apart, were tested for IgG-anti-SARS-CoV-2 (ELISA) and neutralizing (Nab, PRNT50) antibodies. Spike protein-specific T cells were quantitated by IFN-γ ELISPOT and Flow-cytometry-based Intra-cellular-secretion (ICS) for IFN-γ/IL2.Findings: Among pre-vaccination-antibody negative (pre-negatives, n=120) and positive (pre-positives, n=67) COVISHIELD recipients, %Nab seroconversion and median (IQR) Nab titers were 55.1%/95.6% and 16(IQR 2.5-36.3)/(64.5, IQR 34.5-154.2, pst dose, but declined to 1740(911-3116, pnd dose. Though the number of COVAXIN recipients was small, post-2nd dose humoral response was lower than COVISHIELD (50% seroconversion and median titer 6.75, IQR 2.5-24.75, pInterpretation: This first-time, systematic, real-world assessment revealed stronger humoral (COVISHIELD) and cellular (COVAXIN) immune responses respectively. Relation of dose interval and post-2nd decline in Nab titers in pre-positives (COVISHIELD) needs evaluation. Immunogenicity/efficacy of vaccines will change with the progression of the pandemic and needs to be assessed in field-setting.Funding Information: Biotechnology Industry Research Assistance Council (BIRAC), Grant/Award Number: BIRAC/BT/NBM0095/02/18. Declaration of Interests: Authors declare no any commercial or financial conflict of interest.Ethics Approval Statement: The study was approved by the “Human Ethics Committee” of BVDUMCH. Written informed consent was obtained from all the participants.
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