The study showed that if the booster is the same as the first two doses, it boosts immunity well, but when the booster dose is different, the results are not good, an expert privy to the data said, without divulging much details. “There’s no point interfering with the present vaccination drive as results of mixing vaccines are not so encouraging. It’s better to carry on with the same regimen,” another person in the know said.
‘Mix & Match Not Better’
Results were reviewed by the National Technical Advisory Group on Immunisation (NTAGI) in a meeting held last week, Winsley Rose, principal investigator of the study, told ET. “One thing is clear – whatever vaccine we use, it boosts,” he said. “Both (Covishield and Covaxin) are safe. It is not correct to say that a heterologous regime (mix and match) is better than a homologous (same vaccine) regime.”
Rose said CMC will submit trial data to the Drug Controller General of India (DCGI) shortly. “What they want to do with the information is up to them to decide,” he added.
CMC carried out a study that aimed to discover how a fully vaccinated (with two doses) person responded to a booster of another vaccine. It also tracked how mixing and matching Covishield and Covaxin worked in a two-dose regimen. Both the studies were carried out on 200 participants each.
The government has been waiting for the results of both studies to decide on whether to allow mix and match of booster shots or not. India has started giving the same vaccine as the third dose – booster or precaution dose – in the Covid regime and no mixing has been allowed as of now. Those who received Covishield as their first and second dose have been getting Covishield as their third dose. Similarly, those who received Covaxin in their first two doses have got Covaxin as the booster.
Lack of Data
The mix and match approach was not given a go-ahead by the government due to lack of data on its efficacy. The Centre earlier said that as more data on a heterologous approach in the administration of vaccines is received, decisions will be taken accordingly.
Some countries have, however, been testing the vaccine mixing approach. Studies are being undertaken to understand whether mixing two Covid-19 vaccines can result in developing stronger and long-lasting immunity against the infection.