Monday, 09 August 2021 | PNS | New Delhi
The Indian Council of Medical Research (ICMR) has said that a study on mixing and matching of two Covid-19 vaccines — Covaxin and Covishield — showed better immunogenicity than two doses of the same vaccine.
The study was conducted on 18 people of Uttar Pradesh’s Siddharth Nagar who mistakenly received doses of two separate vaccines a few months ago.
The finding of the study, which has been uploaded on medRxiv, but is yet to be peer-reviewed showed that immunisation with a combination of an adenovirus vector platform-based vaccine, followed by inactivated whole virus vaccine, was not only safe but also delivered better immunogenicity.
Covishield, manufactured by Pune’s Serum Institute of India, is the adenovirus vector platform-based vaccine, while Covaxin, developed and manufactured by Bharat Biotech and the ICMR, is the whole virus vaccine.
The subject expert committee of the Central Drugs Standard Control Organisation had in July recommended a trial of mixing Covishield and Covaxin. The trial will be conducted by the Christian Medical College in Vellore on 300 healthy volunteers.
While that will be a proper clinical trial to investigate the effectiveness of the cocktail of Covishield and Covaxin, the ICMR’s study titled ‘Serendipitous Covid-19 Vaccine-Mix in Uttar Pradesh, India: Safety and Immunogenicity Assessment of a Heterologous Regime’ was based on the goof-up that took place in May. There was no immediate adverse impact of the mix-up on the beneficiaries.
Now, a further study has revealed that the mix-up has actually worked in their favour as the beneficiaries have more protection than those who have received two shots of the same vaccine.
“Though India so far has followed homologous approaches (two doses of one vaccine) with Covishield and Covaxin, eighteen individuals, under the national programme, inadvertently received Covishield as the first jab and Covaxin as the second,” it said.
“To the best of our knowledge, this is the first study which reports the effects of heterologous prime-boost vaccination with an adenovirus vectored vaccine followed by an inactivated whole virus vaccine,” the researchers said.
The researchers compared the safety and immunogenicity profile of those people who received two doses of different vaccines, against that of individuals receiving either Covishield or Covaxin.
The study showed that the immunogenicity profile against Alpha, Beta and Delta variants in the heterologous group was superior. “We compared the safety and immunogenicity profile of them (18 individuals) against that of those receiving either Covishield or Covaxin. Lower and similar adverse events following immunisation in all three groups underlined the safety of the combination vaccine-regime.
“The immunogenicity profile against Alpha, Beta and Delta variants in the heterologous group was superior and the IgG antibody and neutralising antibody response of the participants was also significantly higher compared to that in the homologous groups,” the study stated.
These findings have an important implication for the Covid-19 vaccination programme wherein heterologous immunisation will pave the way for induction of improved and better protection against the variant strains of SARS-CoV-2, the researchers underlined.
“Such mixed regimens will also help to overcome the challenges of shortages of particular vaccines and remove hesitancy around vaccines in people’s mind that could have genesis in programmatic ‘errors’ especially in settings where multiple COVID-19 vaccines are being used,” they said.
