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There is a scramble for booster shots all over the world, especially with the advent of the Omicron variant. This new Covid-19 variant is believed to escape immune responses, produced by both natural infection and by vaccines. We also know that both vaccine-induced, and infection-induced antibodies wane in a couple of months.
Besides, there is a proportion of the population, say the elderly, immunocompromised and those with underlying comorbidities (patients of malignancies, transplants, heart ailments, chronic kidney disorders, chronic lung conditions, those on immunosuppressives, etc.), who have not been able to mount a robust immune response at all, even after both doses. Breakthrough infections and reinfections have also been observed frequently and there seems no end in sight to this pandemic.
A sizable proportion of the Indian population is yet to be vaccinated with both doses. So, the priority remains to ensure at least two doses for the entire population are administered. Scientific evidence shows that mortality is significantly higher in the unvaccinated group.
After a substantial proportion of the population receives two doses, it seems prudent to offer a booster dose to the population, which has been inoculated early in January 2021 (frontline and healthcare workers) and to the vulnerable group enumerated above. Though children are also lined up to receive their first shots, the booster dose should be prioritised, as children are known to have milder disease.
Another aspect to be considered is the selection of the vaccine for the booster dose. There is consensus that this one should be based on a different platform and not the same as the earlier two doses. This is based on scientific data that the immune response is significantly augmented when a different vaccine (mix and match or heterologous prime boost technology) is used as a booster.
The best responses have been observed when mRNA vaccines (which are currently not available) have been used as a booster. There will be several newer vaccine options in the coming months, including mRNA vaccines. So, it is probably worthwhile waiting for more vaccine options for a booster dose, rather than rushing due to fear of the Omicron.
Breakthrough infections and reinfections have been recorded after booster doses too. Hence, Covid-19 appropriate behavior is the most important factor which will lead us through this pandemic.
All in all, being fully vaccinated is a larger priority at the moment, and only then can we move to administering booster doses!