The Centre has asked the states and Union Territories to increase the time gap between the first and second dose of administering the Covishield coronavirus vaccine to six-to-eight weeks, instead of the 28-day interval that was being followed until now, as research shows that this would make the shots more effective.
The revised interval applies only to Serum Institute of India's Covishield – the vaccine developed by Oxford AstraZeneca — and not to Bharat Biotech's Covaxin, the Centre said in its letter sent on Monday.
"In view of the emerging scientific evidence, the interval between two doses of a specific COVID-19 vaccine, Covishield, has been revisited by the National Technical Advisory Group on Immunization (NTAGI) and subsequently by National Expert Group on Vaccine Administration for COVID-19," the letter said.
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The Centre's letter said it appeared that "protection was enhanced if the second dose of Covishield was administered between six and eight weeks but not later than that.”
The instructions have been sent as round two of the nationwide inoculation drive is in progress to cover people above 60 years of age and those over 45 with other illnesses such as diabetes. These are considered to be the more vulnerable groups.
The total vaccination coverage in India has crossed the 4.5-crore mark till date.
More than 4.5 crore (4,50,65,998) vaccine doses have been administered through 7,33,597 sessions, according to the provisional report till Monday 7 am.
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Meanwhile, the AstraZeneca-Oxford University Covid-19 vaccine got a major credibility boost on Monday as data from a large final-stage trial carried out in the US, Peru and Argentina showed that the vaccine was both safe and highly effective.
More than 32,000 volunteers took part in the trial with a majority of them being from the US. AstraZeneca will now apply for approval of the vaccine in the US. The results of the trial come amid the controversy created in Europe where use of the vaccine was temporarily stopped over safety concerns.
The vaccine, which is also being manufactured at the Pune-based Serum Institute of India was found 79% effective at stopping symptomatic Covid disease and 100% effective at preventing people from falling seriously ill
There were no safety issues regarding blood clots, the company said.
Data from this new trial – run by experts at Columbia University and the University of Rochester in collaboration with AstraZeneca – may also prove useful in reassuring people about how well the vaccine works to protect the elderly against Covid-19 illness, according to a BBC report.
Around a fifth of the volunteers in this trial were over 65 and the vaccine – given as two doses, four weeks apart – provided as much protection to them as to younger age groups, the report said.
