WHO has also recommended an interval of 8 to 12 weeks between the doses. However, it also said that if the second dose is inadvertently administered less than 4 weeks after the first, the dose does not need to be repeated
India on Monday extended the timeline between two doses of the Covishield vaccine to 4-8 weeks from 4-6 weeks until now following what the government said is scientific evidence showing enhanced protection against the novel coronavirus infection.
This comes as AstraZeneca Plc, which developed Covishield jointly with the Oxford University, disclosed a higher efficacy for the vaccine in preventing covid-19 for a four-week interval during a phase 3 trial in the US, Chile and Peru. The efficacy rate is much higher than that of the UK trial announced last November, providing a major boost to the Anglo-Swedish drugmaker.
Covishield is produced by Serum Institute of India for domestic supplies and also for exports through the company’s bilateral pacts and the World Health Organization (WHO)-led Covax global vaccine alliance.
AstraZeneca said the US trial data showed that the vaccine’s efficacy of 79% was achieved when two standard doses were given at an interval of four weeks, while data from the UK trials showed an efficacy of 53% for interval of less than six weeks.
Announcing its decision, India’s health ministry said in view of the emerging scientific evidence, the interval between two doses of Covishield was revisited by the National Technical Advisory Group on Immunization (NTAGI) and subsequently by the National Expert Group on Vaccine Administration for covid-19 (NEGVAC) in its 20th meeting this month.
“During this meeting, the recommendation has been revised to provide a second dose of Covishield at 4-8 weeks’ interval after the first dose, instead of earlier practised interval of 4-6 weeks," the health ministry said in a statement. The revised interval would only be applicable to Covishield and not for Covaxin.
Covaxin, produced by Hyderabad-based Bharat Biotech International Ltd and developed jointly with the Pune-based National Institute of Virology, is the only other covid-19 vaccine to receive the Indian government’s nod for emergency use.
Union health secretary Rajesh Bhushan told all state chief secretaries about the government’s decision on the revised schedule for administering Covishield.
“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," Bhushan said in a letter.
The dosage interval of Covishield has been a matter of debate and, recently, the WHO’s Strategic Advisory Group of Experts on Immunization had said that in light of the observation that two-dose efficacy and immunogenicity increase with a longer inter-dose interval, the WHO recommends an interval of 8 to 12 weeks between doses. It said, however, that if the second dose is inadvertently administered less than four weeks after the first, the dose does not need to be repeated.
Following the recommendation, AstraZeneca in February submitted the clinical trial data of Covishield after requests by regulators and authorities in several countries. Mint earlier reported that the health ministry is considering the dosage interval of Covishield. Though India started its nationwide covid-19 vaccination exercise on 16 January, AstraZeneca indicated that increasing the interval between the two doses would be an added advantage for India in covering more people.
“There is data available for administration of the second dose up to 12 weeks after the first dose from the overseas studies," a company spokesperson said earlier.
According to the WHO, so far, more than 20 million doses of Covishield have been administered in Europe, and more than 27 million doses of the vaccine have been administered in India.