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UK to start study testing Pfizer, AstraZeneca vaccines together

Dive Brief:

  • The U.K. government is starting a study to see what happens if people get one coronavirus vaccine from Pfizer and another from AstraZeneca.


  • Researchers plan to recruit more than 800 people for the study and initially split them into eight groups, studying the effects of mixing vaccines as well as varying the time between doses. Four groups will get their shots 28 days apart, and the other four will get them 12 weeks apart. The study may expand later to include more products, the government said in a release today.


  • The U.K. government is spending 7 million pounds, or roughly $9.6 million, on the study, which will take place at eight sites around the country and draw participants from the national vaccine registry.


Dive Insight:

Countries around the world are scrambling to inoculate their populations as new, more transmissible variants of the coronavirus spread. The ability to use different shots and varied dosing regimens would help speed that process, giving health officials more options to handle demand.

U.K. officials have already shown some flexibility when it comes to vaccinations, focusing on getting first shots into the population and allowing dosing for the second round to be delayed to as long as 12 weeks. In the U.S., officials recommend three weeks between the first and second shot of the Pfizer vaccine and a four-week interval for a vaccine developed by Moderna.

AstraZeneca’s vaccine, developed with Oxford University, isn’t approved in the U.S. In the U.K., regulators cleared the vaccine even though study results were complicated by the fact that some patients got only half a dose to start and volunteers got boosters anywhere from four to 26 weeks after their first inoculation.

U.K. officials stressed that the new trial doesn’t affect the current practice for vaccinations, and people outside the study should continue to get two doses of the same vaccine within a 12-week period. The U.S. also advises against mixing at this time, with officials saying that should happen only under extraordinary circumstances, such as when the brand of the first-dose shot can’t be determined.

In the new U.K. study, four control groups will get two doses of the same vaccine either 28 days apart or 12 weeks apart. Two groups will get the Pfizer vaccine first and another two will get the AstraZeneca vaccine first, again either 28 days or 12 weeks apart.

The study will give scientists more insight into “how we can use vaccines to stay on top of this nasty disease,” said Jonathan Van-Tam, the senior responsible officer for the trial, in the U.K. press release. It’s even possible that combining vaccines will produce a greater immune response, he said.

The potential for better results has also interested scientists who are planning to test the efficacy of combining AstraZeneca’s shot with a component of Sputnik V, developed by Russia’s Gamaleya Center. Reuters reported that clinical trials will begin next week.

The U.K. was the first nation to clear Pfizer’s COVID-19 vaccine, developed with BioNTech, for emergency use in early December. Regulators in the country gave the green light to AstraZeneca’s entry in late December and then in January approved a third vaccine, from Moderna.