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A new study has found that the Covishield-vaccine-elicited immune responses are of higher magnitude and breadth than Covaxin in both seronegative individuals (without prior exposure) and seropositive (with prior exposure) individuals.
Among the two main SARS-CoV-2 vaccines utilized in India, the study noted that Covishield induced higher antibody levels suggesting a more potent and enduring immune response.
Top institutions and researchers were involved in the study — “Immunogenicity of SARS-CoV2 vaccines BBV152(Covaxin) and ChAdOx1 nCoV-19(Covishield) in seronegative and seropositive individuals in India – a multicentre non-randomized observational study” — that has been published recently in The Lancet
This study was done in healthy adults aged 18-45 years at Bangalore Baptist Hospital National Centre for Biological Sciences (NCBS), Institute for Stem Cell Science and Regenerative Medicine (InStem), King Edward Memorial Hospital Research Center (KEM), Symbiosis University Hospital and Research Center (SUHRC), National Chemical Laboratory (NCL), Indian Institute of Science Education and Research Pune (IISER- Pune), and St. John’s Research Institute (SJRI).
Between June 30, 2021 and January 28, 2022, a total of 691 participants in the 18-45 age group across four clinical sites in India were included in the study.
Vaccine-naive participants were administered two doses of either Covaxin at a 4-week interval or Covishield at a 12-week interval per the prevailing government norms.
The primary outcome was the seroconversion rate and the geometric mean titer (GMT) of antibodies against the SARS-CoV-2 spike and nucleocapsid proteins.
The secondary outcome was the frequency of cellular immune responses pre- and post-vaccination.
Explaining the objective of this study, Prof Vineeta Bal from IISER-Pune told The Indian Express that few studies had made comprehensive head-to-head comparisons of both humoral and cellular immune responses elicited by these vaccine platforms.
“These two vaccines administered in India represent 15 per cent of the total Covid-19 vaccine doses administered worldwide. However, there is a paucity of data comparing the immunogenicity of the two vaccines,” researchers have said in the study.
“In addition to greater seroconversion rates, Covishield also elicited higher antibody titers (GMT) than Covaxin in both seronegative and seropositive individuals. Covishield elicited a higher frequency of both CD4 and CD8 T cells while Covaxin elicited mainly CD4 T cell responses,” researchers said in the study.
The researchers have cautioned that 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.
For determining future Covid-19 vaccination policy when pan-coronavirus or sarbecovirus vaccines become available, it becomes important to take into account pre-vaccination immune history of the majority of the vaccinated Indian population.
“Comparison of vaccine platforms stratified by serostatus will also inform vaccine development against future pandemics that are increasingly likely with climate change, ecosystem destabilization and lowering herd immunity due to vaccine hesitancy against both established and newer vaccine regimes,” Prof Bal said.
