Immunogenicity of two COVID-19 vaccines used in India: An observational cohort study in health care workers from a tertiary care hospital

Abstract

COVID-19 pandemic witnessed rapid development and use of several vaccines. In India, a country-wide immunization was initiated in January 2021. COVISHIELD, the chimpanzee adenoviral-vectored vaccine with full-length SARS-COV-2 spike insert and COVAXIN, the whole virus-inactivated vaccines were used. To assess and compare immune response of health-care-workers to COVISHIELD (n=187) and COVAXIN (n=21), blood samples were collected pre-vaccination, 1month post-1/post-2 doses and 6months post-dose-2 and tested for IgG-anti-SARS-CoV-2 (ELISA) and neutralizing (Nab,PRNT50) antibodies. Spike-protein-specific T cells were quantitated by IFN-γ-ELISPOT. In pre-vaccination-antibody-negative COVISHIELD recipients (pre-negatives, n=120), %Nab seroconversion (median, IQR Nab titers) increased from 55.1% (16, 2.5-36.3) post-dose-1 to 95.6% (64.5, 4.5-154.2, p<0.001) post-dose-2 that were independent of age/gender/BMI. Nab response was higher among pre-positives with hybrid immunity at all-time points (p<0.01-0.0001) and independent of age/gender/BMI/Comorbidities. Post-dose-2-seroconversion (50%, p<0.001) and Nab titers (6.75, 2.5-24.8, p<0.001) in COVAXIN-recipients were lower than COVISHIELD. COVAXIN elicited a superior IFN-γ-T cell response as measured by ELISPOT (100%; 1226, 811-1532 spot forming units, SFU/million PBMCs v/s 57.8%; 21.7,1.6-169.2; p<0.001). At 6months, 28.3% (15/53) COVISHIELD and 3/3COVAXIN recipients were Nab-negative. T cell response remained unchanged. During immunization, COVID-19 cases were detected among COVISHIELD (n=4) and COVAXIN (n=2) recipients. At 6months, 9cases were recorded in COVISHIELD-recipients. This first-time, systematic, real-world assessment and long-term follow up revealed generation of higher neutralizing antibody titers by COVISHIELD and stronger T-cell response by COVAXIN. Diminished Nab titers at 6months emphasize early booster. Immunogenicity/efficacy of vaccines will change with the progression of the pandemic needing careful evaluations in the field-settings.

Interim results from comparison of immune responses elicited by an inactivated and a vectored SARS-CoV-2 vaccine in seronegative and seropositive participants in India

“…In every virus variant tested, Covishield TM elicited higher responses than Covaxin â . The superiority of vectored vaccines over inactivated vaccines for antibody responses against SARS-CoV-2 has been demonstrated by other studies [7][8][9][10][11] . Further, inactivated viral vaccines have historically been of lower immunogenicity, requiring 4 doses in the primary series for the inactivated polio vaccine and the rabies vaccine.…”

“…Prior studies comparing Covishield TM and Covaxin â were limited to addressing only antibody responses and in particular in the health care worker population who were immunized prior to the delta wave [7][8][9][10][11] (See Supplementary Table 1). There is however, limited data on cellular immune responses elicited by these vaccines and no direct headto-head comparisons or stratification by pre-vaccination serostatus 11 . Vaccination following exposure to the Delta or Omicron variants of SARS-CoV-2 is likely to affect the quality, quantity and duration of immune responses.…”

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“…Another study by Vidya Arankalle et al found that at 6 months of post vaccination, 71.7% COVISHIELD and 0% COVAXIN recipients were Nab-positive. 11 The variation of persistence of Nab could probably because of the efficacy variation of the subjected vaccine candidates & demographic dynamics of the study populations.…”

“…A relatively low percentage of Nab in our study probably because of lower number of study subjects.In this context study by Vidya Arankalle et al reported lower titre of Nab in both the pre & post vaccination infective individual in comparison to Covishield Vs Covaxin vaccinees, the study group found significant(p<0.001) in this. Though it was mentioned that the study group among Covaxin vaccinees was comparatively lower 11.…”

Variable neutralizing antibody responses to 10 SARS-CoV-2 variants in natural infection with wild- type (B.1) virus, Kappa (B.1.617.1), and Delta (B.1.617.2) variants and COVISHIELD vaccine immunization in India: utility of the MSD platform

“…The samples used for this study represent a subset of samples collected earlier for the evaluation of the immune response of healthcare personnel to COVID-19 vaccinees ( 21 ). Of these, samples with sufficient volumes (n=135) were selected for the study.…”