FAQ: Where Do Countries Stand on Mixing Vaccines? Is It Safe?

Is mixing and matching COVID vaccines a good idea? These countries seem to think so.

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(This article has been updated and republished from The Quint’s archives after the DCGI gave its approval to conduct a study on mixing India's two main vaccines, Covaxin and Covishield. This was first published on 14 July.)

The Drugs Controller General of India (DGCI) has given its approval to conduct a study on mixing Covaxin and Covishield, news agency ANI reported on Wednesday, 11 August.

India's Central Drugs Standard Control Organisation had on 29 July recommended clinical trials to study the mixing of these two vaccines.

Let's look at what studies have found so far, and how different countries are approaching this.


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 had said, "Vaccine are not medications, instead they actually evoke targeted responses from the body. Mixing vaccines usually does not cause any problems."

Despite 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 vaccines based on preliminary study results.


Where do different countries stand on mixing and matching vaccines?


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 vaccines in fully vaccinated adults as a booster shot.

The trial results are expected in late summer 2021.


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.


In January, the British government updated it's COVID vaccination guidelines, stating that people may mix and match their two 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, had announced the launch of clinical trials to explore if mixing shots of the COVID 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.



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.


According to a Wall Street Journal report, dozens in Dubai and Abu Dhabi, who had been fully inoculated with the Sinopharm vaccine, are being revaccinated with the Pfizer-BioNTech's jabs as a booster shot.


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 the AstraZeneca vaccine to take one of the approved mRNA vaccines as their second dose.


What is the WHO saying about this?

The World Health Organization's head scientist Soumya Swaminathan addressed an online press briefing on Monday, 12 July, and referred to the fast-emerging trend of mixing and matching of different COVID-19 vaccines as "dangerous", advising beneficiaries against it.

"It's a little bit of a dangerous trend here. We are in a data-free, evidence-free zone as far as mix and match (is concerned)."
Soumya Swaminathan

She added, "It will be a chaotic situation in countries if citizens start deciding when and who will be taking a second, a third and a fourth dose," Reuters reported.

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.

(With inputs from FIT)

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