As COVID continues to surge in parts of the world and our arsenal of vaccines runs low, countries have turned to seriously consider the possibility of mixing and matching COVID-19 vaccines.
This question of the efficacy—and more importantly the safety—of doing so, has become more pertinent now in the face of vaccine rollout delays in countries like India slowing down the innoculation drive with partially vaccinated people left hanging for their second doses.
Moreover, new waves of COVID and the threat of new variants breaching the vaccine's protection has led to the possible need for a third booster dose being looked at.
Let's look at what studies so far have found, and the countries that have opened up to the mixing and matching of vaccines.
Is It Safe to Mix-and Match Vaccines?
Several clinical trials are currently underway around the world to test the safety and effectiveness of mix-and-match vaccines.
Though these studies are still in early stages, preliminary data points to it being safe.
Preliminary data from a recent study led by researchers at the University of Oxford found that 'mixing' the Oxford-AstraZeneca and Pfizer-BioNTech vaccines is safe, although it could cause more severe, albeit temporary, side effects.
"Importantly, there are no safety concerns or signals, and this does not tell us if the immune response will be affected."Matthew Snape, Associate Professor in Paediatrics and Vaccinology, University of Oxford
Speaking to FIT for a previous article, eminent immunologist Dr Satyajit Rath said, "Vaccine are not medications, instead they actually evoke targeted responses from the body. Mixing vaccines usually does not cause any problems."
But in spite of this, experts in India have expressed their reservations when it comes to allowing the mix-and-match of COVID vaccines in the face of shortage, on the grounds that there isn't sufficient clinical data.
Some countries, on the other hand, have already allowed the mix-and-match of vaccine based on preliminary study results.
Where Different Countries Stand on Mixing and Matching Vaccines
USA
On Tuesday, 1 June, the US became the latest country to announce the beginning of clinical trials to test the use of a different COVID vaccine in fully vaccinated adults as a booster shot.
The trial results are expected in late summer this year.
Canada's National Advisory Committee on Immunization (NACI) on 1 June, in updated guidelines, announced that people who received a first dose of the AstraZeneca vaccine may receive Pfizer-BioNTech or Moderna for their second, reported IANS.
UK
In January, the British government updated it's COVID vaccination guidelines saying people may mix and match their two COVID-19 shots, in case they are unaware of the vaccine they received, or the vaccine they received as their first dose is not available.
The UK, in February, announced the launch of clinical trials to explore if mixing shots of the COVID-19 vaccines by Pfizer and Oxford-AstraZeneca will provide equal or better protection than giving the same vaccine twice.
They have also allowed for Pfizer and Moderna vaccines to be used interchangeably.
Bahrain
Despite having high levels of vaccination in the country, the island nation of Bahrain has had an alarming spike in COVID cases and deaths in recent weeks, prompting them to start giving Pfizer-BioNTech booster shots to vulnerable residents who were fully vaccinated with the Chinese Sinopharm vaccines.
UAE
According to a Wall Street Journal report, dozens in Dubai and Abu Dhabi, who had been fully inoculated with the Sinopharm vaccine, are being reinoculated with the Pfizer-BioNTech's vaccine as a booster shot.
Spain
After the study conducted by CARLOS III Health Institute showed encouraging preliminary results in early May, Spain allowed those who have received one dose of the AstraZeneca vaccine to receive a second dose of the Pfizer vaccine.
Apart from these, France, Norway, and Sweden have also allowed those who have taken one dose of AstraZeneca vaccine to take one of the approved mRNA vaccines as their second dose.
India
As of now, India does not recommend the mix-and match of COVID vaccines, citing a lack of clinical data.
However, when cases of vaccine mix up in parts of Uttar Pradesh and Gujarat raised concerns of safety, all the experts FIT spoke to said there are no likely major concerns about the actual safety and side effects of doing so. However, they were clear that without clinical data and study, no policy can be formed.
“My guess is that the mixed regimen will also provide reasonable protection, but we should not be using it in the absence of evidence and regulatory approvals,” Dr Rath said.
No official announcement of trials to test the safety and efficacy of mix-and-match vaccines in the country have been made as yet.
(Written with inputs from Reuters, the Wall Street Journal and IANS.)
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