Researchers looking into possible benefits of people receiving two different coronavirus vaccines

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Fri, 2021-06-25 14:41 — mike kraft

The most widely used coronavirus vaccines are designed as two-shot inoculations, and nearly everyone worldwide who has had both doses has received the same vaccine both times.

But that is changing, as more countries are allowing — and even, in some cases, encouraging — mix-and-match inoculation, with people receiving a first shot of one vaccine, and then a second shot of a different one. On Tuesday, Germany’s government revealed that Chancellor Angela Merkel had received two different shots, adding to the growing interest in the practice.

Some nations have tried that approach out of necessity, when supplies of a particular vaccine ran short; or out of caution, when questions were raised about the safety of a shot after some people had already received their first doses. U.S. regulators so far have been reluctant to encourage the practice.

But scientists and health policymakers are interested in the possibility that giving different shots to the same person could have significant advantages.

Mixing vaccines — scientists call it “heterologous prime-boost” — is not a new idea, and researchers have experimented with it in fighting a handful of other diseases, like Ebola.

Scientists have long theorized that giving people two slightly different vaccines might generate a stronger immune response, perhaps because the vaccines stimulate slightly different parts of the immune system or teach it to recognize different parts of an invading pathogen.

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

Multiple clinical trials are currently underway to determine whether there are benefits or drawbacks. Researchers at the University of Oxford are testing different combinations of vaccines — including the AstraZeneca-Oxford, Pfizer-BioNTech, Moderna and Novavax shots — in the Com-Cov trial, and the U.S. National Institutes of Health recently launched a trial of mixed booster doses.

Russian researchers are testing a combination of their Sputnik V vaccine and the AstraZeneca shot. Sputnik is, itself, somewhat based on a mix-and-match approach, with the first and second shots having different formulations.

Most studies are still in early stages, but some have released promising preliminary results. ...

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