Clarity on mixing covid jabs likely by Jan

CMC Vellore is nearing the end of its study on mixing doses, including of Covaxin and Covishield, said Gagandeep Kang, leading virologist and professor at the medical research institution.

Research has shown that mixing two different vaccine platforms such as an mRNA platform and an adenovirus platform (eg; Pfizer and AstraZeneca vaccines) provides better immune response to the SARS CoV-2 virus. India’s study, the first of its kind, will find out whether the inactivated and adenovirus platforms also offer similar response.

The study involving 1,100 participants that began in August took time due to the mandatory 12-week gap between the vaccine doses, an official aware said on condition of anonymity, adding the initial vaccine shortage lengthened the wait.

The study’s clinical protocol says it aims to explore the advantages of a flexible immunization programme, where the second dose is not necessarily same as the first dose and the vaccine intervals too are similar.

“This study will determine the safety as well as the immune responses to mixed administration of Covishield following Covaxin and vice-versa given at an interval of 56+/- 7 days and make comparisons with the same two-dose administration of these two vaccines,” according to details that Mint has viewed.

Safety and immune responses will also be determined following the mixed booster dose administration of available vaccines after an interval of 3-6 months after the second dose.

The second leg of the study on mixing booster doses is now recruiting participants.

The US Food and Drug Administration has recommended mixing of Johnson & Johnson vaccine (an adenovirus vaccine) with Moderna’s mRNA vaccine, as part of its boosting strategy. In October, an FDA advisory said that a “single booster dose of any of the available covid-19 vaccines may be administered as a heterologous booster dose following completion of primary vaccination with a different available covid-19 vaccine… The eligible population(s) and dosing interval for a heterologous booster dose are the same as those authorized for a booster dose of the vaccine used for primary vaccination”.

India is yet to decide on giving booster doses, despite demand from healthcare workers citing their high risk.

But unlike other countries, which have based their booster strategy on available data, India has not released any data on the population-level vaccine effectiveness.

“There is no incentive for vaccine makers to carry out such studies such as vaccine effectiveness; that is why we need the government to carry out such a study so that we can take an informed decision on boosters and population level immunity,” Kang added.