Expert groups – the National Technical Advisory Group on Immunisation (NTAGI) and the National Expert Group on Vaccine Administration for Covid-19 (NEGVAC) – are studying scientific evidence and deliberating on the need for booster vaccine shots against Covid-19 in the country. The Christian Medical College (CMC), Vellore is conducting a study to look at which of the two main vaccines available in India – Covishield and Covaxin – can be a better booster shot. The study could not find an adequate number of trial participants who have taken Covaxin, prompting Dr Gagandeep Kang, a leading researcher and microbiologist from CMC, to put out an appeal on social media. “Folks in Vellore, Chennai, Bangalore or Delhi willing to consider participating please email email@example.com,” she said. On Sunday, HT spoke to Dr Kang about the ongoing study and the available evidence on boosters. Excerpts:
What is the status of CMC Vellore’s ongoing study on boosters?
We started recruitment for the trial in September. We are taking people who have received two doses of either Covishield or Covaxin and then randomly assigning them to receive a booster dose, more than three months later. The idea is to prepare for a programme for India on boosting. We want to make sure that mixing and matching is okay and have some idea of what the performance is like.
We had no problem in getting people who have got Covishield, but we had a problem finding enough people who have received two doses of Covaxin and willing to be in the trial. The study was getting delayed since we are having trouble finding people in Vellore, so we are now looking at recruiting people outside Vellore, who we can run the study on and follow up on the phone.
If we finish recruitment fast, we get the results fast. While it was okay to keep doing things at the pace we were doing them earlier, now with Omicron coming, I really think we can shorten the time to results. It’s an advantage for all of us.
The Covishield results are ready, but because it’s a trial of both vaccines, we can’t unblind it until we finish the Covaxin arm.
Going by data emerging from different parts of the world, which vaccines are most suited for boosters?
Right now, all we are measuring is antibody responses. And if we look at antibody response measurement, the Messenger RNA (mRNA) vaccines give the highest level of antibodies either as primary series or as boosters. So, you have to have the mRNA vaccines somewhere in the mix. For instance, if you boost with AstraZeneca on an mRNA-base vaccine, that also gives a high value. Having an mRNA vaccine in the mix of either primary or booster series seems to be showing up as important. But remember that this is only antibody response and we not talking about the T cell response here.
Then there are protein vaccines, but we don’t know what the antibody levels will be like with the Indian protein vaccines. But hopefully, we will have that data soon.
And then there are vectored vaccines and inactivated virus vaccines. Covaxin in the clinical trial seems to have higher antibodies than the Chinese inactivated vaccine.
With the emergence of the new Omicron variant, can we afford to wait for Indian data to roll out a booster policy?
For the immunocompromised, we should have rolled out a third shot dose or the booster, months ago. I have been saying this for a while now. The immunocompromised need better vaccination strategies, they need more doses. You can’t use a one-size-fits-all strategy, when you know that certain groups have extra vulnerability.
We don’t have the mRNA vaccines in India. But we can think about the priority population first by giving them what is available. By then we will have data from our study being conducted at CMC Vellore, among healthy people, and it will tell us which is a better vaccine to boost with.
So, if India does allow boosters, Covishield or Covaxin can be used for third doses?
Every vaccine will boost, it’s a question of which vaccine is the best. If you have vaccines that give a high and long-lasting response, then you will need to boost less often. So that’s what we should aim for. But in the absence of data, in the absence of knowledge about what might be best for our population given our prior exposure, it’s difficult to make a final policy now.