New Delhi: There has been considerable debate over why the gap between doses of the Covishield vaccine has been changed since it was first used in India four months ago.
As per the latest guidelines, the second dose of Covishield – the Oxford-AstraZeneca vaccine being manufactured by Serurum Institute in India – can be administered 12 to 16 weeks after the first dose.
On the other hand, Bharat Biotech-developed and manufactured entirely desi vaccine Covaxin has always had only a four-week gap.
Why is there such a significant difference in the two vaccines?
According to Indian Council for Medical Research (ICMR) head Dr Balram Bhargava, the gap between two doses of Covaxin has remained unchanged because the immunity achieved after the first shot is not as high as in other vaccines.
Justifying the Centre’s decision to make the 3-month gap for Covishield mandatory, Bhargava said that it was found that the immunity after the first shot of Covishield was quite 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 was quoted as saying in a report by The Times of India.
He stressed that scientists and experts are still in the learning stages as far as vaccines against the coronavirus are concerned.
“Vaccines against Covid-19 first came on December 15. We are very new, and still 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 told The Hindu.