After two doses, Covishield vaccine produces more antibodies against spike protein of Sars-CoV-2, the virus causing Coronavirus disease (Covid-19), than Covaxin, found a pre-print study based on real-world data among health care workers in the country.
Data of 515 vaccinated health care workers, across 21 cities in 13 states was analysed from across India between January and May 2021, of which 425 had taken Covishield and 90 took Covaxin vaccine.
The study that is currently online on open-access journal, medrxiv, found that “among the 515 HCW (305 Male, 210 Female), 95.0% showed seropositivity after two doses of both vaccines. Of the 425 Covishield and 90 Covaxin recipients, 98.1% and 80.0% respectively, showed seropositivity. However, both seropositivity rate and median (IQR) rise in anti-spike antibody was significantly higher in Covishield vs. Covaxin recipient…”
In effect, while both vaccines elicited good immune response after two doses, although seropositivity rates and median anti-spike antibody titre was significantly higher in Covishield compared to Covaxin arm.
Both the vaccines studied are currently being given under the national Covid-19 immunisation programme in India.
According to the study, overall combined results of both vaccines showed 95% seropositivity to anti-spike antibody, 21-36 days after the second dose.
Serum Institute of India (SII) is locally producing Oxford-AstraZeneca vaccine under the brand name Covishield, and Covaxin is co-developed by Bharat Biotech and the Indian Council of Medical Research (ICMR).
The primary aim of the researchers was to analyse antibody response (seropositivity rate and median [inter-quartile range, IQR] antibody titre) following each dose of both vaccines and its correlation to age, sex, blood group, body mass index (BMI) and comorbidities.
“While no difference was observed in relation to sex, BMI, blood group and any comorbidities; people over 60 years or age or those with type 2 diabetes had a significantly lower seropositivity rates.”
The research was led by Dr Awadhesh Kumar Singh, consultant endocrinologist, GD Hospital and Diabetes Institute, KolKata, West Bengal.
However, fewer post-vaccination infections, also known as breakthrough infection, were seen in health care workers who took Covaxin, corroborating the other possibility of the vaccine having better cell-mediated response.
“Breakthrough infections (defined as SARS-CoV-2 infection >2 weeks after the second dose) were reported in 4.9% (24/492) of cases following both vaccines. Breakthrough infections were noted in 5.5% (22/399) cohorts in Covishield and 2.2% (2/93) of Covaxin recipients. Majority had mild (28/30) to moderate (2/30) Covid-19 infections and all recovered,” found the study.
The phase II trial results of Covaxin published in the Lancet Infectious Diseases showed enhanced humoral and cell-mediated immune responses.
According to a paper on immunology published in ScienceDirect, cell mediated immunity does not involve antibodies but rather incorporates the activation of macrophages (a type of white blood cell of the immune system that engulfs anything that doesn’t have, on its surface, proteins that are specific to healthy body cells) and natural killer cells enabling them to destroy intracellular pathogens