Experts question 9-month gap for boosters, say immunity declines after 4-6 months of jab

Amid rise in Covid-19 infections, experts are questioning the government mandated nine-month gap between the second vaccination shot and the precaution or booster dose, as they call for a shorter gap on the grounds that immunity declines after 4-6 months of the jab.

"On balance, during a pandemic with variants coming up regularly, a booster at six months is possibly better," said Shahid Jameel, virologist and Fellow, OCIS and Green Templeton College, University of Oxford.

Jameel said the logic for a longer gap is that it produces a better immune response. "But we know that neutralising antibodies decline to background levels in about six months," he said.


According to the WHO, a booster dose of Covishield and Covaxin - the two main vaccines used in India - may be considered 4-6 months after completion of the primary vaccination series.

In other countries

• US: Booster 5 months after primary vaccination series
• UK: Three months after second dose
• Germany: Three months after last vaccination
• Australia: Three months after primary course of vaccination

The benefits of booster dose have been recognised following increasing evidence of waning vaccine effectiveness against SARS-CoV-2 infection over time. "Decline in immunity after vaccination occurs in 4-6 months, that is when a booster shot is required," said Anoop Misra, chairman, Fortis C-Doc, a Delhi-based hospital.

Poonawalla, Ella Pitched for 6-mth Gap
Experts do not see any scientific logic behind the longer gap of nine months between the second dose and the third dose.

"I really don't understand why this decision on the booster interval was made," said Chandrakant Lahariya, an epidemiologist and public policy specialist.

The decision to go for a nine-month gap was taken in December when the government began the precaution dose for the elderly as well as frontline and healthcare workers. Government officials say at that point, a lot of people were still looking to get the second dose. Also, a large proportion of people had acquired immunity through natural infection in the second wave. "There were also plans to open up vaccination for children. Hence, it was felt appropriate to go for a nine-month gap," said a senior official.

Since it worked well, the government decided to continue with the same duration when the booster dose was allowed for all adults from April 10 this year.

While the move to allow the third dose for all above 18 years of age has come at a time when some parts of the country have started seeing an uptick again, many are not able to take the benefit due to the nine-month duration rule.

Adar Poonawalla, CEO of Serum Institute of India (SII), recently urged the government to reduce the gap.

"The gap between the second Covid vaccine jab and third (booster dose) should be brought down to six months, against the current 270 days (nine months)," Poonawalla said.

"Only those who have taken a second dose in (or before) August will be eligible for boosters. If reduced to six months, a lot more people become eligible for the dose," Poonawalla had said. According to him, in all other countries, including European nations, the gap between two doses is six months or less.