The protein-based vaccine when given as a booster shown to induce not only increased antibody response but also robust T-cell and B-cell (memory cell) response linked with long-term immunity
Amidst the concerns of a new covid wave in India following a massive surge in cases across China, Japan, South Korea, the US and Brazil, researchers at the AIG Hospitals, Hyderabad have published results of a significant scientific study proving the immunity benefits of indigenous heterologous vaccine booster, Corbevax in combating Omicron variants.
The study titled ‘Heterologous Booster Dose with CORBEVAX Following Primary Vaccination with COVISHIELD Enhances Protection against SARS-CoV-2’ was published in the high-impact factor journal “Vaccines.”
Breaking down the key aspects of the study, Dr D Nageshwar Reddy, Chairman, AIG Hospitals and one of the researchers on board said, “We knew from our previous studies that mixed vaccines produce better immune response; therefore, when the government approved Corbevax to be given as a heterologous booster to individuals already vaccinated with COVISHEILD, we aimed to determine how a different vaccine platform (protein-based) will impact the immune response, especially in the context of the Omicron variant. Our study was done on 250 healthcare workers who had received two doses of Covishield as the primary vaccine regimen not more than six months ago.”
Corbevax is an indigenously developed peptide-based vaccine which is different from the Viral vector (COVISHEILD) or the inactivated vaccine (COVAXIN). The key difference is that Corbevax uses only a protein subunit of the virus replicated inside a yeast cell while the others are whole virus vaccines. The advantage of peptide-based vaccine is that it considerably reduces the risks of allergic and autoimmune responses making them safe for widespread usage.
Dr Reddy further added that “the first aspect was to test the safety of this combination. We are happy to report that none of the 250 participants had any adverse events following the administration of Corbevax booster dose. This further cemented our belief that mixed vaccines are safe. The second aspect of the study was to measure the antibody response as well as the T-cell (memory cell) response at 30 days and then at 90 days to correctly estimate the overall protection against the circulating Omicron variant.”
When estimating the effectiveness of a vaccine, both the antibody response and T-cell (Memory cell) response are essential. “In our study, we compared the immune responses among those individuals who were given the same vaccine, i.e., COVISHEILD (homologous group) as a booster and those who were given Corbevax as a booster (heterologous group). The S1/S2-spike protein IgG antibody levels and T/B Cell response of these groups were compared at 30 days and at 90 days. While the homologous and heterologous groups showed increased S1/S2-spike protein IgG antibody level at 30 days, the heterologous group (Corbevax as a booster) showed higher levels of antibodies at both 30 days and 90 days,” Dr Reddy said.
Another significant finding of the study is regarding the memory cells which account for long-term immunity against the virus. The researchers used advanced flow cytometry to measure T and B Cell responses.
The study quotes “CD4-T lymphocyte responses were higher at day 30 and day 90 in individuals receiving heterologous booster with Corbevax in comparison to individuals receiving homologous booster with Covishield. While CD4-T lymphocyte increased at day 30, (62.92 ± 12.8) and remained consistent until day 90 (64.85± 8.72) (p = 0.0001) in individuals who received heterologous booster with Corbevax, CD4-T lymphocyte response increased at day 30 (day 30, 66.2 ± 12.4) as compared to pre-booster dose (day 0, 46.2 ± 12.43) and decreased in individuals who received homologous booster Covishield at day 90 (day 90 51.66 ± 10.03) (p = 0.0001).”
Explaining the findings, Dr Reddy said, “It is evident from the results that heterologous booster with Corbevax elicited better memory cell responses in individuals and the levels didn’t decrease at 90 days compared to the homologous group.”
The effectiveness of the heterologous booster with Corbevax is also evident in the clinical findings. Out of the 250 participants, 10 individuals turned out to be COVID-positive beyond 30 days after the booster dose. “The significant impact of Corbevax as a booster was seen in the clinical setting where COVID-positive individuals from the heterologous group showed minimal/mild symptoms whereas the homologous group did develop symptoms such as fever/body pains, cold, and cough,” Dr Reddy said.
The biggest takeaways from the study are as follows:
- Corbevax as a booster dose (third dose) is safe and significantly more effective than repeating the initial vaccine regimen.
- The heterologous (mixed vaccine) booster elicits better immediate antibody response and also produces long-lasting memory cell response against variants of SARS-COV-2.
- The study was undertaken when Omicron variants are circulating in India; therefore, it would be appropriate to say that a heterologous booster (Corbevax) would be effective in combating any wave that is fueled by sub-variants of the Omicron.
- High-risk group people should consider taking the booster dose and continue to take COVID-appropriate precautions all the time, especially when in public spaces.
