Britain has appealed to other members of the Group of 20 nations to classify clinical trial volunteers as vaccinated, but most haven’t done so.

Britain announced Friday that it will offer new vaccinations to thousands of people who volunteered for trials of the Novavax coronavirus vaccine, which hasn’t yet been approved for use in any country, the AP reports.

Around 15,000 people in the U.K. got Novavax shots as part of a clinical trial. While the U.K. recognizes them as vaccinated, most countries don’t, meaning they can’t travel.

Britain’s health department said more than 15,000 participants will be given two doses of the Pfizer/BioNTech vaccine. The government says it plans to expand the offer to about 6,000 U.K. participants in trials of other vaccines that also haven’t been approved for use.

Britain has appealed to other members of the Group of 20 nations to classify clinical trial volunteers as vaccinated, but most haven’t done so.

England’s deputy chief medical officer, Jonathan Van-Tam, noted that “if more countries around the world had reciprocated by allowing U.K. volunteers to enjoy fully vaccinated status for overseas travel, these measures would not have been necessary.”

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