Serum Institute of India CEO Adar Poonawalla has said that the effectiveness of the Covishield vaccine rises to as much as 90 per cent if the two shots are separated by about 2.5-3 months.
Interestingly, a study in The Lancet published earlier this year had claimed that the vaccine, developed by AstraZeneca in collaboration with Oxford University, had an efficacy of 70 per cent with one month gap between the doses.
“One arm of trials, in which doses were given one month apart, was 60-70 per cent effective. And there was another group of few thousand patients where they gave a gap of 2-3 months between the two doses. That is where they found the efficacy to be 90 per cent,” Adar Poonawalla told India Today TV.
“If you look at other vaccines as well, the longer gap you keep between the doses, the better their efficacy,” Poonawalla further said.
Last month, the government decided to increase the interval between the first and second doses of Covishield to up to eight weeks upon the recommendation of the National Expert Group on Vaccine Administration.
The group relied on data from trials of AZD1222 in other countries, which found that the efficacy of the vaccine increased when the second dose was given more than six weeks after the first.
Poonawalla also said that immunity kicks in one month after taking the first dose of the Covishield vaccine. The vaccine works by using a weakened version of a common cold chimpanzee adenovirus.
“We found an excellent response below the age of 50 with one dose. We can say after a month, even with one dose, there is excellent protection, more than even what you find in a Covid-19 recovered patient. About 70 per cent of people are fully protected with one dose, but the second dose is necessary for long-term immunity protection,” he said.
“However, even after the second dose, everybody should wear masks, maintain social distancing till a treatment is available for the disease or till we reach a certain level of herd immunity, which will take a few years,” the Serum Institute chief said.
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