Extending the interval between Covid vaccine doses could leave people vulnerable to infection by one of the many variants of the virus currently in circulation, Dr Anthony Fauci, the medical advisor to the President of the United States, told NDTV Friday.
Top Covid expert Dr Fauci was responding to a question about recommended intervals between vaccine doses in the light of revised guidelines by the Indian government last month.
“The ideal interval between doses for the mRNA vaccines is three weeks for the Pfizer and four weeks for the Moderna. The problem with extending this is that you in between the doses you become vulnerable to variants,” Dr Fauci told NDTV.
“… and we’ve seen that in the UK, where they extended that interval, in that period you can get infected by the variants. So we recommend staying on schedule,” he explained.
Dr Fauci also clarified that “if you have a very small supply of vaccines” it may be necessary to extend the interval between doses.
Last month the government extended the gap between doses of the AstraZeneca vaccine (manufactured and sold in India as Covishield) to 12-16 weeks – from the existing six-eight weeks.
No changes were announced for Bharat Biotech’s Covaxin.
“Based on available real-life evidence, particularly from the United Kingdom, the COVID-19 Working Group has agreed to increase dosing interval between two doses of Covishield to 12-16 weeks,” the government said in its statement.
That was the second time in three months Covishield dosage intervals were widened; in March states and UTs were told to increase the gap from 28 days to six-eight weeks “for better results”.
Widening of Covishield dosage intervals have been linked to increased efficacy.
A study published in international medical journal The Lancet on February 19 claimed a 26.2 per cent increase – from 55.1 per cent to 81.3 per cent – if doses were spaced 12 or more weeks apart.
However, the changes came amid an acute shortage of doses (a shortage that continues to affect the country’s vaccination pace) as manufacturers Serum Institute struggled to match demand.
The timing of the recommendations sparked suggestions the government was trying to eke out current stocks, and give as many people as possible at least one dose till supply can be replenished.