CMC Vellore to conduct Covishield-Covaxin mix study

A top Indian hospital is set to launch a mix-and-match clinical trial involving Covishield and Covaxin in order to find out whether a single dose of two vaccines could be combined for an effective protection against the Covid-19 epidemic.

To be conducted by scientists at the Christian Medical College, Vellore on 500 individuals, the trial would involve giving 200 persons with the first shot of Covishield followed by Covaxin and inoculating the two shots in reverse order to another 200 recipients.

In both groups, the second shot will be administered two months after the first jab.

The remaining 100 persons would be split into two groups of 50 each who would receive two doses each of Covishield and Covaxin. The scientists would subsequently analyse the immune responses in all the four groups to determine the best combination.

"We should have the initial set of results before the end of 2021,” principal investigator Winsley Ross at the CMC told DH. The Drugs Controller General of India. has recently approved the study design which would be having a second arm focusing on the need to have a booster dose.

Also read: DCGI gives nod to study on mixing Covaxin and Covishield

In the boosting arm of the study, around 600 persons who have already received two doses of either Covishield or Covaxin, would be given a booster dose after six months to check if such a strategy improves the vaccine’s ability to protect the recipients from hospitalisation and serious disease.

The plan is to create three groups of 200 volunteers each who would receive booster shots of (1) Covishield (2) Covaxin and (3) any new vaccine that may come to the market later this year. Each group would be followed up for six months. The exercise has been funded by the Azim Premzi foundation.

"We will carry out immunogenicity studies in great details,” said Gagandeep Kang, eminent virologist and a professor at CMC. A common information sharing platform would be created using which other scientists working on the vaccines can measure their immune responses following the same standard for better assessment of the two vaccines.

"The World Health Organisation has called for a moratorium on booster dose for the time being. We are closely watching the science on the need for such a dose. It is a work in progress,” V K Paul, NITI Ayog member and the government’s principal advisor on Covid-19 said on Tuesday.

Earlier scientists at the Indian Council of Medical Research studied 18 individuals who by mistake received Covishild as the first dose and Covaxin as second. The ICMR study, even though conducted on a small sample, demonstrated the superiority of the Covishield-Covaxin combination as against the two doses of the same vaccine.

"These findings have an important implication for the Covid-19 vaccination program wherein heterologous immunisation will pave the way for induction of improved and better protection against the variant strains of SARS-CoV-2. Such mixed regimens will also help to overcome the challenges of shortfall of particular vaccines,” the ICMR team reported.

India has administered more than 52 crore Covid-19 vaccine doses so far, of which over 45 crore are Covishield and the rest is Covaxin. More than 40 crore individuals received the first dose whereas 11.53 crore got both the shots.