Amid growing hue and cry by some states over supply of Covid vaccines, the Centre is planning to tweak its strategy to ensure people are provided with jabs as early as possible to develop herd immunity. According to a report in The Indian Express, the government will review the impact of its recent decision to extend the Covishield doses' interval by collecting data from a Covid vaccine tracker platform that is yet to be launched. The platform will be launched shortly through which the government will collect data related to people who are being inoculated as per the new schedule.
Sources said that the data may also help the government decide whether to approve a single-dose regimen for Covishield, the IE report said. Covishield is the local version of the Oxford-AstraZeneca COVID-19 vaccine. It is being manufactured by the Pune-based Serum Institute of India. It is a two-dose vaccine and the government recently increased the gap between two doses to 12-16 weeks.
Covishield is made from an adenovirus isolated from chimpanzee poop which has been genetically changed so that it doesn't grow in humans. It is a viral vector vaccine. The gap between two doses of Covishield was 6-8 weeks before the recent increase. According to studies, initially, the interval between two doses of Covishield was 4-6 weeks but then as more data became available, secondary analysis showed that increasing the dosage interval to 4-8 weeks can have some additional advantage.
It is being said that the decision to increase the gap will enhance protection against Covid in an individual if the second dose of Covishield is administered between 12-16 weeks. According to the Covid-19 Working Group's claim, this is a dynamic decision and part of a periodic review. The decision is based on the available real-life evidence that suggested that the interval should be extended to 12-16 weeks.
What expert said
Dr NK Arora, chairman of the Covid working group under the National Technical Advisory Group on Immunisation (NTAGI), told the IE that the data from the new platform is expected to be analysed around August.
Arora said that the platform will have three sets of administrative data in terms of diagnostic data, vaccine data and the overall disease data are to be harmonised.
"Based on that, we will look at vaccine effectiveness, reinfections and trends as vaccine coverage increases,” the IE report quoted Arora as saying.
Arora said that a study on mixing two different vaccines will also be done to study the efficacy. The study will be completed in 2-2.5 months.
"India may soon start in few weeks testing feasibility of a regimen that mixes 2 different doses of Covid vaccines to see if it helps boost immune response to virus," he said.
Any decision regarding a single-dose regimen or mixing doses will help the government to cover the population faster with its vaccination drive. According to the government's submission in the Supreme Court, the entire eligible population will be vaccinated by 2021-end, adding that production from domestic vaccine producers - SII, Bharat Biotech and Reddy's Lab will be enough to vaccinate all who are over 18 years of age.
All the vaccines including those being used in India for inoculation are two-dose drugs. Only Johnson and Johnson has developed a single-dose vaccine. The American pharma major's vaccine is also based on the viral vector platform. Sputnik V too is based on the same technology but is given in two doses. Notably, the Oxford-AstraZeneca vaccine had initially started rolling out the vaccine in a single-dose, but calibrated as a two-dose vaccine based on efficacy reports.