An expert panel of the government is considering increasing the gap between two doses of Oxford-AstraZeneca’s Covishield vaccine.
Top government sources have told News18 that the panel is reviewing new evidence from international studies that suggest the vaccine’s efficacy is improved if the interval between the two doses is longer. The committee is likely to take a decision next week.
The recommended interval between the two doses of Covishield, manufactured by Pune’s Serum Institute of India (SII), was increased from four-six weeks to six-eight weeks in April.
Experts believe such a move could ease pressure on the vaccine’s supply chain at a time when India has decided to include all adults in its massive inoculation programme against the coronavirus disease (Covid-19).
In March, a study published in The Lancet journal said Covishield has an 81.3% efficacy if doses are administered 12 weeks apart. Researchers found Covishield’s efficacy to be just 55.1% when two standard doses were administered less than six weeks apart.
According to data from late-stage trials in Britain and Brazil, the vaccine is up to 90% effective when given as a half dose followed by a full dose at least a month later. But there is not enough data to put this idea to work.
Countries such as the UK and Canada administer the two doses of the vaccine 12 weeks and 16 weeks apart, respectively. Experts point out that the vaccine leads to improved immune response with a gap in the time period.
If the interval is increased in India, it will help the country on two fronts.
First, it could ease the skyrocketing demand for vaccines in the backdrop of India making all adults eligible for the shot from May 1. With more candidates on the way — other than SII’s Covishield and Bharat Biotech’s Covaxin that are currently in use — the move could address a crippling supply crisis that many states have complained of.
Second, if the rush for the second dose slows down, officials could focus on vaccinating more beneficiaries with the first dose, which gives some degree of protection before the second dose is administered. For example, recent data by the Korea Disease Control and Prevention Agency (KDCA) showed the AstraZeneca vaccine is 86.0% effective at least two weeks after a first dose among people aged 60 and older.
The primary analysis of the Phase III clinical trials from the UK, Brazil and South Africa confirmed the vaccine is safe and effective, “with no severe cases and no hospitalisations, more than 22 days after the first dose”, AstraZeneca said on its website on February 3. Results demonstrated vaccine efficacy of 76% after a first dose, with protection maintained to the second dose. “With an inter-dose interval of 12 weeks or more, vaccine efficacy increased to 82%,” it added.
As of May 6 morning, India’s cumulative vaccination coverage had exceeded 16.25 crore with over nine lakh beneficiaries of the 18-44 age group getting the jab.