NEW DELHI: The Centre on Monday instructed all states to increase the interval between two doses of Covid-19 vaccine Covishield to 6-8 weeks based on recommendations by the expert panels, which have now heeded international evidence that had been ignored earlier.
Keeping the existing scientific evidence in view, the Union government said, it appears that protection is enhanced if the second dose of Covishield is administered between 6-8 weeks, but not later than the stipulated period of eight weeks.
Scientific evidence from some countries shows that while the vaccine is about 60-65 % effective at a gap of four weeks, it can be up to 90 % effective against infection when given at an interval of 12 weeks.
The Centre's directions apply immediately, which means that all the beneficiaries who have taken the first dose but are due for the second, can follow the new advisory.
The two-dose Covishield vaccine by AstraZeneca-Oxford University, being manufactured and marked by the Serum Institute of India, is currently being administered to beneficiaries at a gap of four-six weeks in the country.
Since the launch of the Covid-19 vaccination drive in the country on January 16, Covishield has been the main vaccine that has been administered to 90 % of the beneficiaries so far.
"In view of the emerging scientific evidence, the interval between two doses of a specific Covid-19 vaccine Covishield, has been revisited by National Technical Advisory Group on Immunization and subsequently by National Expert Group on Vaccine Administration for Covid-19 vaccine," the union ministry of health and family welfare said.
During this meeting, the recommendation has been revised to provide the second dose of Covishield at four-eight weeks' interval after the first dose, instead of earlier practiced interval of four-six weeks, it added.
The government also said that this decision of revised time interval between two doses is applicable only to Covishield and not to Covaxin, the other vaccine being used in the vaccination drive.
The letter sent by the Union health secretary Rajesh Bhushan to the chief secretaries of the states on said that the government had accepted the recommendations of NTAGI and NEGVAC and advised them to ensure the administration of the dose of Covishield to beneficiaries within this stipulated time interval of four-eight weeks after the first dose.
Bhushan also asked states to direct 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.
Based on the evidence from several countries, the World Health Organisation in early February had said that the two doses of this vaccine should be given at a gap of eight-twelve weeks.
Incidentally, the instructions by the Indian government on Covishield come on a day when results from a large-scale clinical trial from the US have shown that the vaccine is 79 % effective against asymptomatic infection and 100 % effective against severe disease.