There will be no mix-and-match of vaccines for those eligible to get a 'precautionary' third dose, Dr VK Paul, the head of India's Covid task force, said Wednesday.
This means individuals who received two doses of the Serum Institute's Covishield will get the same vaccine this time, and those who got Bharat Biotech's Covaxin will get a third jab of that vaccine.
The 'precautionary' dose - announced by Prime Minister Narendra Modi last month after sustained demand for vaccine boosters in the light of the Omicron threat - is, for now, only available for frontline and healthcare workers, and those over 60 with co-morbidities, starting January 10.
Vaccines for children in the 15-18 age group (another long-standing demand) began Monday, with Covaxin. The government has cleared one other vaccine for kids - Zydus Cadila's ZyCoV-D - but it is unclear when it will be available.
Dr NK Arora, the chief of the country's immunisation programme, told NDTV this week the question of choice of 'precautionary' vaccine doses would be "based on the science of what (is) the best option".
"... basically based on the science of what would be the best one and available experience within the country, and it will be transparently available and informed to the community," he said.
Calls for booster doses, at least for those who are at increased risk of contracting, or re-contracting, the virus, increased after the emergence of the Omicron variant, which is widely believed to be both more infectious and more resilient to existing vaccines.
Well before the Indian government authorised boosters, or 'precautionary' shots, several other countries had already done so, including the United States and the United Kingdom.
On paper eight vaccines cleared for use in India, including US pharma giants' Moderna and another by Johnson & Johnson but only two - Covishield and Covaxin - have been used.
An overwhelming majority of Indians have received the former, i.e., Covishield.
Last week two more were added to the 'on paper' list - Corbevax, described as India's first homegrown "RBD protein sub-unit vaccine", and Covovax - as well as the anti-viral drug Molnupiravir.
Corbevax and Covovax - are unlikely to be used for booster shots, Dr Arora told NDTV.
India has, so far, administered nearly 147 crore doses, of which around 61.8 crore are second doses.
The government's decision to not mix-and-match vaccines follows the World Health Organization saying it is advisable to ensure people get the same drug they were initially given.
In July last year the WHO's Chief Scientist, Dr Soumya Swaminathan, said mixing and matching vaccines was "a bit of a data-free, evidence-free zone."
Mixing and matching of vaccines should only be done if there is a supply constraint, the WHO said.
Vaccine combinations, already used by some governments, could help low- and middle-income countries manage stockpiles and deal with vaccine shortages as the Omicron variant spreads.
The European Union has endorsed the mixing of two different shots for both initial vaccine schedules and boosters, and the United States, in October, said it would allow 'mix-and-match' boosters.
This morning India reported 58,097 new cases over the previous 24 hours; this includes 243 cases of the Omicron variant. This morning's overall daily Covid case count was the sixth increase in nine days.
With input from Bloomberg