In the first of its kind study since the launch of the AstraZeneca's Covishield and Bharat Biotech's Covaxin in the country, the Indian Council of Medical Research (ICMR) will conduct a survey from next week to examine the effectiveness of these vaccines in preventing progression of COVID into a severe form.

"As a part of the study we will take people who are COVID-19 positive and hospitalised and compare their vaccination status with those who have tested COVID negative," Bhatnagar said.

"The aim is to assess how effective vaccination is in preventing progression of the disease into a severe form," he said.Noting that this is first of its kind study since the launch of these vaccines in the country and used in India's inoculation drive, Bhatnagar said the survey is expected to be undertaken from next week.

The cumulative vaccine doses administered in the country has crossed 20 crore so far.The Central government has been urging people to get vaccinated, maintaining that the vaccine will not protect one from contracting the coronavirus infection but will prevent its progression to a severe form and thereby reduce mortality.

The government has also been stressing on the need to wear a mask and adherence to other COVID protocols.As of date, India is using three vaccines against COVID-19 in its immunization drive. These include Covishield manufactured by the Pune-based Serum Institute and Covaxin of Bharat Biotech in Hyderabad.

The Russian Sputnik V is the third vaccine to get approval from the Drug Controller General of India (DCGI) for Emergency Use Authorisation and has been used in a few private hospitals so far.