Explained: Why Covaxin dose gap not increased like Covishield?

The Centre again revised the gap between the two doses of Oxford-AstraZeneca’s Covishield – a COVID-19 vaccine manufactured by the Serum Institute of India (SII) last week.

At the beginning of the vaccination drive in January, the two doses were meant to be administered with a gap of four-six weeks. Later, the Centre revised it to four-eight weeks. Last week, it said that the doses of the vaccine are to be administered 12-16 weeks apart, following a recommendation by a government panel, saying it was a “science-based decision”.

The central government has lately come under a lot of criticism over the new rule that increased the gap between two doses of Covishield vaccine to 12-16 weeks, from the earlier 8-week gap, while there were no changes in the dosage interval for Covaxin.

The ambiguity over the decision has now been cleared by Dr Balram Bhargava, the head of Indian Council for Medical Research, who said that the gap between both the doses of Covaxin was unchanged as the immunity achieved after the first shot is not as high as the other vaccines.

Bhargava, justifying the Centre’s decision to make the 3-month gap for Covishield mandatory, said that the immunity found after the first shot of the vaccine manufactured by Serum Institute of India was found to be strong.

“On the other hand, immunity level after the first shot of Covaxin is not as high and this means the second dose should be taken after four weeks to ensure full efficacy,” Bhargava said.

“Vaccines against Covid-19 first came on December 15. We are very new, and are learning…trials are still on. It is an evolving science. By giving the first dose of Covaxin, you do not achieve too many antibodies. You achieve it after the second dose. With Covishield, antibodies are achieved at good levels,” Bhargava said.

Commenting on the government’s suggestion that people who have been infected and recovered from Covid-19 can wait for three months before taking their vaccine shot, the ICMR chief said that it was based on an assessment which claimed that the recovered people will have antibodies.

“It is not clear how long the antibodies last. So, it is advised that vaccination be completed after a 3-month interval,” he added

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