Decision to increase gap between COVISHIELD doses taken on scientific evidence: NTAGI

Almost after a month of increasing the gap between two doses of Covishield to 12-16 weeks, Chairman of India's COVID-19 Working Group of the National Technical Advisory Group on Immunisation (NTAGI), Dr. N K Arora, on Wednesday said that decision was taken 'on scientific evidence in a transparent manner'. Explaining the decision further, Dr. Arora added that the efficiency differed from 65% - 88%. According to the NTAGI official, increased intervals of vaccines also showed better results. 

Dr. Arora cited the example of the UK while explaining the scientific evidence. 

"In the last week of April, 2021 the data released by Public Health England, United Kingdom’s executive agency of the Department of Health, showed that vaccine efficacy varied between 65% - 88% when interval is 12 weeks. This was the basis on which they overcame their epidemic outbreak due to the Alpha variant. The UK was able to come out of it because the interval they kept was 12 weeks. We also thought that this is a good idea, since there are fundamental scientific reasons to show that when interval is increased, adenovector vaccines give better response. Hence the decision was taken on May 13, to increase the interval to 12 - 16 weeks,” Dr. Arora was quoted speaking. 

The official further highlighted India's vaccination system as 'open and transparent' and marked that the decision was taken with 'no dissenting voice'. While answering the question of why it was not done before, Dr. Arora added that the advisory group was waiting 'for ground-level data from the UK (the other biggest user of AstraZeneca vaccine)'. The NTAGI Chief also cited the examples of Canada, Sri Lanka and few other countries justifying India's decision to follow the same. 

India to revert to four or eight weeks interval?

While answering the above-mentioned question, Dr. Arora added that discussions are going on since mid-May if 'India should revert to four or eight weeks'. 

Dr. Arora further compared the efficiency between two doses of vaccine adding the example of AstraZeneca vaccine which gives only 33% protection with the first dose and two doses give about 60% protection. NTAGI is monitoring the response of the vaccination programme and type of vaccine and interval between doses, and what happens when someone is fully / partially immunized, as decided by the advisory team.

"Vaccine effectiveness 75% for both partially immunized and fully immunized"

While referring to a study by PGI Chandigarh, and CMC Vellore, Tamil Nadu Dr. Arora added that "study very clearly shows that vaccine effectiveness was 75% for both partially immunized and fully immunized" resulting in similar effects to those who received only one dose of vaccine or both. However, this is particularly regarding the Alpha variant, which proved devastating in Punjab, Northern India, and Delhi.