Are there benefits to mixing Covishield and Covaxin?

Fluctuating supplies and logistical hurdles are among the reasons for the push for vaccine mixing in India, say experts

The Drugs Controller General of India (DCGI) has given its approval for conducting a study on the mixing of Covaxin and Covishield Covid-19 vaccines in India, news agency PTI reported.

The study will be conducted by the Christian Medical College, Vellore and will involve 300 healthy volunteers. Prior to this, the Indian Council of Medical Research (ICMR) has revealed in its study that the combination of Covaxin and Covishield vaccines has elicited better safety and immunity results. The two vaccines available in India use different platforms – Covishield is an adenovirus vector platform-based vaccine, while Covaxin is an inactivated whole virus vaccine.

“For a country like India with a large population, getting everyone vaccinated as soon as possible is the only way we can push the third wave. But doing so is proving to be a logistical challenge. The fluctuating supplies might be one of the reasons for the push on mixing vaccines,” says Dr Pruthu Narendra Dhekane, infectious diseases consultant, Fortis Hospital, Bannerghatta Road.

‘Can increase immunity’

Dr C Nagaraj, director, Rajiv Gandhi Institute of Chest Diseases, Someshwarnagar, says the push for the mixing of vaccines is a welcome one. He says the studies conducted abroad and even in India by the ICMR suggest that mixed vaccines provide greater protection against new variants.

“Two doses of Covishield have a success rate of 91% and one dose of Covaxin has 92%. Since Covishield is said to be less effective on other variants, the mixing of two vaccines is more ideal as the success rate is 95%,” he explains. This will also help solve the shortage issues faced by Covaxin, he
believes.

Vaccine mixing is currently being practised in various countries across the world. “The effectiveness depends from country to country depending on the different variants, now, we should see how it works for India,” he says.

Dr Raghu J, internal medicine and infectious diseases specialist, Sakra World Hospital, Marathahalli, is also in favour of the “vaccine cocktail”. “I definitely suggest people to try mixing their doses, as it not only boosts a better immunogenic response against the virus, it also has more efficacy. When the vaccines were mixed, the production of antibodies to fight against the virus was six times higher as opposed to the same vaccine doses,” he says.

But he warns that mixing vaccines might come with its own set of drawbacks. “It might result in side-effects like extra fatigue and headaches, but otherwise, no major concerns,’’ he explains.

Limited data

According to the World Health Organization, there is currently limited data on the immunogenicity or efficacy of a “mix and match” regimen.

“Studies like this take time. If research had been started back in January for example, we would’ve had had proper details right now to figure if vaccine mixing works or not, as we’re in the need to vaccinate. But due to lack of data back then, no such research was conducted and we’re only getting to it now,” says Dr Subramanian Swaminathan, director, infectious diseases, BGS Gleneagles Global Hospital, Uttarahalli. He believes that while a study conducted with only 300 people will be useful research, it will fall short at the clinical level.

“A study of this size does not provide enough data for mixing of vaccines to be accepted clinically. For example, if the study proves that taking Covishield as the first dose and Covaxin for the second dose increases immunity, it does not necessarily mean it would work the same way if the doses were inverted. All these factors need to be taken into consideration,” he says, suggesting for a much larger study to be conducted with clearer data.

The mixing of vaccines can also lead to problems among the manufactures, regarding cost and profit sharing and also leading to a blame game, in case of any mishaps.

“This may open up a portal to more problems, rather than solving them and simplifying the process. There is also the issue of Covaxin not yet being accepted by WHO. So, if a vaccinated person, having taken one dose of each vaccine wants to travel, what happens in such a case?” he questions. The trial needs to appear in a peer-review journal to be considered legitimate.

The focus right now should be on getting as many people vaccinated as possible, instead of looking into newer researches, says Dr Dhekane.

“We have limited data on mixing vaccine and its effects but we already do know that taking two doses of the same vaccine does provide good immunity and efficacy, so we should focus on that and get people vaccinated faster,” he says.