Statistically significant data from CMC Vellore based on thousands of cases during the Delta outbreak shown a 61% effectiveness with a single dose of Covishield and 65 per cent with two doses.
The information was revealed by NK Arora, Chairperson of the Indian government's Covid Working Group.
Amid a heated debate on the wide gap India is taking between the first and second dosages of the Covishield vaccine, it has been revealed that data from Indian trials suggest the 12-16 weeks interval was medically sound. In comparison, data from the UK, which has been used to suggest otherwise was statistically less relevant to India, according to Dr Arora.
"When we started with the national Covid immunisation programme...we had an interval of four weeks. That was based on the trial showed that, at a four-week interval, the immune response is very good. Although the UK, at that time, had already increased the interval to 12 weeks. That was the time they were facing the challenge of the Alpha variant outbreak and they were having a tough time in December-January," Dr Arora said, reports the NDTV.
"But we were not convinced and we went ahead with four weeks. Six weeks later the WHO also suggested that 6-8 weeks may be a good idea. We reviewed the data and we had initial experience from the UK and we thought that it may worthwhile to increase it to 6-8 weeks," he said.
However, the working group decided to look at the real-life data coming in from the UK, since that country and India are the largest consumers of the AstraZeneca vaccine -- Covishield in India.
In April, he said, Public Health England, suggested that with a 12-week interval, the vaccine efficacy was varying between 65% to 80%. This was the worst period of the Delta variant outbreak in India.
"We took the decision on 6th or 13th of May, and within two days we learnt that Public Health England had...decided that they showed that, with one dose, the protection is 33%," Dr Arora said.