The government has increased the time interval between the two doses of Covishield the Oxford-AstraZeneca vaccine against Covid-19, being manufactured locally by Serum Institute of India from four-six weeks to four-eight weeks in view of the “emerging scientific evidence”.
The recommendation came from the National Technical Advisory Group on Immunisation, which revised its view on the issue, and subsequently by the National Expert Group on Vaccine Administration for Covid-19, the Union health ministry said on Monday.
As per a statement, the decision has been taken in view of the emerging scientific evidence. Notably, the new guidelines are only applicable to the Covishield vaccine and not the Covaxin coronavirus vaccine.
Union Health Secretary Rajesh Bhushan wrote a letter to the Chief Secretaries of States/UTs on Monday, asking them to ensure the administration of second dose of Covishield to beneficiaries within the stipulated time interval of 4-8 weeks after the first dose.
“Keeping the existing scientific evidence in view, it appears that protection is enhanced if the second dose of COVISHIELD is administered between 6-8 weeks, but not later than stipulated period of 8 weeks,” read a statement.
“The Union Health Secretary has urged the States and UTs to instruct the concerned officials accordingly to undertake necessary steps to widely disseminate the message of revised dosing interval amongst programme managers, vaccinators and recipients of COVISHIELD vaccine and ensure adherence of the revised dosing interval,” the statement added.
Oxford-led clinical trials from the UK, Brazil, and South Africa confirmed the vaccine had 76 per cent efficacy three weeks after the first dose that is maintained to the second dose.
The efficacy increased up to 82 per cent with longer inter-dose interval of at least 12 weeks or more.
According to a study published in a British medical journal, the vaccine’s efficacy reached 82.4 per cent after a second dose in people with a dose interval of 12 weeks or more. If the two doses were given less than six weeks apart, the efficacy was only 54.9 per cent.
So far, 4.50 crore doses of coronavirus vaccine have been administered in the country since the drive began on January 16 after approval for Covishield and Covaxin.