Should you mix and match vaccines to combat the delta variant?

mix and match COVID vaccines
Photo via Tim Reckmann/Flickr (CC BY 2.0)

Mix and match inoculations are on the rise, as countries around the world use whatever COVID vaccine they have available to help citizens reach full vaccination. Even German Chancellor Angela Merkel switched up her vaccine brand for her second shot, starting in April with a dose of AstraZeneca and polishing off her inoculation in late June with a dose of Moderna. This practice is becoming more common, but is it as effective as sticking to the same manufacturer for both doses?

Experts in the U.S. remain wary of the mix and match COVID vaccine method, but other nations believe the practice could be beneficial. The idea of mixing vaccines is nothing new and, in fact, has been common practice for decades.

Also called “heterologous prime-boost,” mixing and matching vaccines is theorized to potentially boost immune response. Arguments lean on the idea that different vaccines stimulate different parts of the immune system, potentially bolstering the body better than two doses of the same vaccine. This could also help in combating the delta variant, which is quickly becoming the dominant strain in countries around the globe.

This theory has been tested on a number of other diseases, including ebola, according to the New York Times. It has yet to be tested on COVID-19, but some experts believe the practice could aid in fighting the virus. 

“The argument is that one and one makes three,” John Moore, a virologist at Weill Cornell Medicine, told the New York Times. “How well that argument holds up in practice in the COVID area is going to need to be judged by the actual data.”

In the U.S., scientists are interested in the potential benefits of mix and match COVID vaccines, but in other parts of the world, the practice is a necessity. In countries with less access to vaccines or where delays have stalled vaccine rollout, mixing doses is becoming a common practice. 

The ability to mix and match COVID vaccines has allowed some countries, including Germany and Canada, to massively ramp up inoculations among their citizens. No negative health outcomes have yet been linked to the practice, but studies are underway to ensure that no recipients will suffer as a result of their mixed dosage.

Clinical trials in the U.S., U.K., and Russia are showing promising results, and they may indicate whether mixed doses can boost vaccine efficacy against the delta variant.

There may be a few short-term disadvantages for those who mix and match their COVID vaccines. Studies indicate that recipients of mixed doses may experience more severe side effects following a vaccine, including increased risk of fever, headache, and fatigue. Despite the potential side effects, researchers expect their studies to prove that mixing vaccines is safe.

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Sources: New York Times, Express

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