Will a booster shot provide the turbocharge for Covid immunity that India is looking for? Maybe in an ideal situation where most people are fully vaccinated but not when less than a quarter of the adult population has received both doses, say experts.
As the global debate on booster shots gathers momentum, several scientists here said the priority must be to ensure that more people are inoculated with at least their first jab.
Immunologist Satyajit Rath said that less than 15 per cent of Indian adults have been vaccinated with two doses, and this clearly means that all Indians who are more vulnerable to infection have not yet necessarily gotten two doses.
"I therefore think that it is ethically premature to begin planning a third dose to a fortunate category of people at this stage, Rath, from New Delhi's National Institute of Immunology (NII)," told PTI.
It is also pragmatically premature to do so, since we have no really clear idea of who is 'more vulnerable to infection'. We do know that some co-morbid categories are more vulnerable to serious illness, but two doses of the current vaccines currently protect quite well against that, he explained.
Immunologist Vineeta Bal agreed, saying India should not think of providing booster doses at this stage when about 40 per cent of the eligible population is yet to receive the first dose.
"In her view, vulnerable people, those with co-morbidities, may be considered for additional shots on a case by case basis. But it has to be remembered that additional shots do not cover specific variants, which are supposed to be more dangerous," Bal, guest faculty at Pune's Indian Institute of Science Education and Research, told PTI. Hence the utility of an additional shot will be limited, in terms of expanding immunity, she argued.
Though India has not yet rolled out the third dose, there are reports some healthcare workers and politicians in Mumbai have taken a booster shot.
Indian Council of Medical Research (ICMR) Director General Balram Bhargava said earlier this week that a booster dose is not the central theme at the moment and getting two doses remains the major priority.
On Friday, India administered a record over 2.5 crore COVID-19 vaccine doses, taking the cumulative number of doses administered in the country to 79.33 crore, according to data on the co-WIN portal. With this, an estimated 63 per cent of India's adult population has received its first dose and 21 per cent are fully vaccinated, official sources said.
According to Rath, all current Covid vaccines in use worldwide remain very effective for protection against serious illness or death from the infection, without any booster doses.
While antibody levels are indeed going down after a few months, this is neither surprising nor does it necessarily indicate any substantial loss of this kind of protection. How much longer it will be before any such loss begins to be seen is an empirical question for which we will have to wait for data, the scientist added.
Identifying population groups with an increased risk of infections within a fully vaccinated population is necessary to minimise the death rate, said researcher Naga Suresh Veerapu.
The reasons for booster doses may differ by population groups at risk, type of vaccine, waning immunity, variants of concern, and clinical and epidemiological settings, said the associate professor, Department of Life Sciences, School of Natural Sciences (SNS), Shiv Nadar University, Delhi-NCR.
There is an argument for booster shots if countries have the luxury to administer them.
The need has been emphasised due to concerns over waning immunity provided by vaccines and also the rise of the Covid variants, especially the Delta strain.
A recent study by ICMR-regional medical research centre (RMRC), Bhubaneswar, found that the level of antibodies produced among Covaxin recipients starts to decline after two months, while the same for those who have been vaccinated with Covishield starts after three months.
Similar results have been found for many other vaccines internationally. Pfizer and Moderna earlier this week said protection from their vaccines can wane over time.