Covid-19 vaccine: Govt defends 12-16 week interval for Covishield doses

Around 90% of the total Covid-19 vaccines administered in the country are Serum Institute of India’s Covishield vaccines.

The government on Wednesday defended the decision to increase the interval between two doses of the Covishield vaccine from 12 to 16 weeks saying it was based on a fundamental scientific reason regarding behaviour of adenovector vaccines. This was a unanimous decision taken by the Covid-19 Working Group and Standing Technical Sub-Committee (STSC) of National Technical Advisory Group on Immunisation (NTAGI).

The government was responding to reports which suggested the decision to increase the gap between two doses of Covishield vaccine from 6-8 weeks to 12-16 weeks was not unanimous and that there had been some dissent among technical experts over this. The dissenting members had reportedly pointed to the lack of data to support extension of the gap beyond 12 weeks and were more comfortable with a gap of 8-12 week between the two doses.

Around 90% of the total Covid-19 vaccines administered in the country are Serum Institute of India’s Covishield vaccines. The dosage schedule was changed from four to six weeks in January to 4-8 weeks in March and then during April and early May the gap was six to eight weeks. On May 13, during the second wave of the pandemic, the interval was increased to 12-16 weeks. This was done at a time when the UK reduced the gap between the two doses to deal with rise in infections due to the Delta variant.

The 22nd meeting of Covid-19 working group of the NTAGI was held on May 10 to consider a proposal for a change in the interval for Covishield used under the national vaccination policy. The group recommended that ‘based on the real-life evidences particularly from the UK, the Covid-19 working group had agreed to increase the interval to 12-16 weeks between two doses. This recommendation of Covid-19 working group was further taken up for discussion in the meeting of STSC which was held on May 13. The STSC of NTAGI went by the Covid-19 working group recommendation and a dosing interval of minimum three months between two doses of Covishield vaccine was recommended.

During both these meetings, the government said no dissent was shown by any of the member, including Dr Mathew Varghese, Dr MD Gupte or Dr JP Muliyil. WHO had fixed the gap between two doses for this vaccine at 12 weeks and the UK, too, had a 12-week gap.