The decision to keep the interval between the second and third doses at nine months has been based on the findings of five scientific studies carried out by the Indian Council of Medical Research (ICMR) and the Translational Health Science and Technology Institute (THSTI), Faridabad, top government sources who were part of the deliberations, told The Indian Express.
The nine-month interval would mean the initial doses of the precautionary vaccine will be received by those who had got the second shots in the primary vaccination schedule by April 10 this year — that is, mainly the healthcare and frontline workers who were the first to be inoculated from January 16 onward.
On March 1, India also began vaccinating those older than 60 years, and 45-plus with specified co-morbid conditions. As of May 1, 1.11 crore people had received both doses, according to Health Ministry data.
“The Co-win platform will automatically reflect who will be eligible for the precautionary dose. We have the numbers ready as to how many will be eligible from January 10. An announcement will be made in the next few days,” a top government official said.
The sources drew a distinction between the precautionary doses planned by India from January 10, and the “booster” shots that are being administered by several countries around the world, including the United States and United Kingdom.
In his address to the nation on Saturday night, the Prime Minister did not use the expression “booster”; he said three priority groups — healthcare workers, frontline workers, and those above 60 with associated comorbidities — would get a “precautionary dose” of the vaccine.
“Two doses of a two-dose vaccine (such as Covishield or Covaxin) may not produce a sufficient level of antibodies in individuals who are immunocompromised or immunosuppressed — their primary vaccination is, therefore, deemed incomplete,” a source said.
“To complete the primary vaccination for this specific group of immunocompromised and immunosuppressed individuals, an additional shot is required.”
Globally, the words booster doses and additional doses refer to different things, the sources said. “Booster doses are used on a population-wide basis; they are administered irrespective of the physical (comorbidity) status of the beneficiary,” a source said.
“Since we (India) do not have extensive population-based data on a booster shot, we are, as a measure of abundant caution, giving vulnerable groups that are exposed or could be exposed to the virus, another shot, which is the precaution dose,” the source said.
According to the sources, a few members of the National Technical Advisory Group on Immunization (NTAGI) were against the administration of booster doses due to “insufficient pan-India” data on waning immunity post the second dose across all age groups.