BENGALURU: While the jury is still out on how long antibodies produced after vaccination will remain in the body, several countries are talking of booster doses to beat the highly transmissible, emerging variants of SARS-COV-2, like the Delta variant.
However, former head of the Indian SARS-CoV-2 Consortium on Genomics (INSACOG) and virologist, Dr Shahid Jameel, told TNIE that there is a need for more studies on this front in India. He said booster doses of the same adenovirus vaccines may not be a good idea and that the country should either try a new combination of vaccines as booster doses, or wait for more studies.
According to Dr Jameel, “From a virological and immunological point of view, it may not be a good idea to give a booster dose of an adenovirus vaccine. The reason simply is that adenoviruses are very highly immonogenic and our body, after two doses, will have already produced a lot of antibodies against the adenovirus background. Hence, a third booster dose of the same vaccine is not likely to be very effective.”
Although laboratory studies are yet to be conducted in this regard, Dr Jameel said the third dose of the same adenovirus vaccine is unlikely to do much. “Hence, the third dose, if required, has to be a different vaccine.” The major vaccines used in India are Covishield and Covaxin, besides the Russian vaccine Sputnik-V, which is on a similar platform as Covishield.
Interestingly, in April, Bharat Biotech, the makers of India’s Covaxin, got permission from the Drug Controller General of India to conduct trials for a third shot to be administered as a booster dose. The trial is ongoing with the first result likely to be out in August and the final one expected by November. According to Bharat Biotech’s reports, the booster shot might become a yearly thing to keep the immune system at the optimum level.
Dr Jameel said the third shot of vaccine could be a combination of “either Covaxin, for those who have taken Covishield, or any other mRNA vaccine, or the protein vaccine. Novovax, which is being manufactured by Serum Institute of India (SII), has shown excellent results, so that could also be a right choice.”
He said the government should wait for more scientific studies to be conducted before rushing in to mix and match vaccines, as existing ones have shown to be beneficial even against the new variants of concern. However, some other experts who are closely following the vaccine scenario, say that in the current situation, they see a potential for increasing vaccine-escape virus mutations.
“The original blueprint of current vaccines has been using the D614G (mutant strain) and new variants could potentially overcome this in the coming months. Many companies have already been working towards a modified vaccine or a new one, too. This seems more of a possibility than a booster,” said Dr Vishal Rao, Regional Director, Head Neck Surgical Oncology and Associate Dean, Centre of Academics and Research HCG Cancer Centre, who is also a member of the Covid-19 Genomic Surveillance Committee.