Scientific evidence suggests that protection is enhanced if the 2nd dose of COVISHIELD is administered between 6-8 weeks, but not later than the stipulated period of 8 weeks
Previous trials have shown that an extended interval of up to 12 weeks demonstrated greater efficacy, which was also supported by immunogenicity data
Based on experts' recommendations, the Indian government has written to states and Union Territories to increase the gap between two doses of Serum Institute of India's locally made Oxford Covid-19 vaccine 'Covishield' from earlier 4-6 weeks to 4-8 weeks now.
"In view of emerging scientific evidence, the interval between two doses of a specific COVID-19 vaccine i.e. COVISHIELD, has been revisited by National Technical Advisory Group on Immunization and subsequently by National Expert Group on Vaccine Administration for COVID-19," the government stated.
"This decision of the revised time interval between two doses is applicable ONLY to COVISHIELD and NOT to COVAXIN Vaccine," the government stressed/
The letter also stated that scientific evidence suggests that protection is enhanced if the 2nd dose of COVISHIELD is administered between 6-8 weeks, but not later than the stipulated period of 8 weeks.
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 to the revised dosing interval.
At the beginning of this year, the drug controller of India had given emergency use authorisation to two Covid-19 vaccine candidates –Serum's Covishield and Bharat Biotech's indigenously manufactured Covaxin – ahead of the mega vaccination drive that kickstarted on 16 January, 2021.
The total vaccination coverage in India has crossed the 4.5-crore mark till date.
More than 4.50 crore (4,50,65,998) vaccine doses have been administered through 7,33,597 sessions, as per the provisional report till Monday 7 am.
Meanwhile, earlier today, a large trial in the US and two South American countries of the Oxford-AstraZeneca vaccine has shown 79% efficacy rate at preventing symptomatic COVID-19 and 100% effectiveness in stopping severe disease and hospitalisation, the biotech firm said.
A Phase III study of the vaccine, developed by Oxford University and produced by AstraZeneca was conducted by AstraZeneca plc in the US, Chile and Peru and reaffirmed that the vaccine is “safe and highly effective", adding to previous trial data from the UK, Brazil and South Africa.
The Oxford/AstraZeneca vaccine is also being produced as part of a tie-up by the Serum Institute of India.
Previous trials have shown that an extended interval of up to 12 weeks demonstrated greater efficacy, which was also supported by immunogenicity data.
The latest trial included two doses administered at a four-week interval, which evidence suggests administration of the second dose with an interval longer than four weeks could further increase efficacy and accelerate the number of people who can receive their first dose.
The vaccine can be stored, transported and handled at normal refrigerated conditions for at least six months and administered without the need for preparation within existing healthcare settings.
AZD1222 was co-invented by the University of Oxford and its spin-out company, Vaccitech. It uses a replication-deficient chimpanzee viral vector based on a weakened version of a common cold virus (adenovirus) that causes infections in chimpanzees and contains the genetic material of the SARS-CoV-2 virus spike protein.
After vaccination, the surface spike protein is produced, priming the immune system to attack the SARS-CoV-2 virus if it later infects the body.
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