LONDON • British authorities recommended Wednesday that the AstraZeneca COVID-19 vaccine not be given to adults under 30 where possible because of strengthening evidence that the shot may be linked to rare blood clots.

The recommendation came as regulators both in the United Kingdom and the European Union emphasized that the benefits of receiving the vaccine continue to outweigh the risks for most people — even though the European Medicines Agency said it had found a “possible link” between the shot and the rare clots. British authorities recommended that people under 30 be offered alternatives to AstraZeneca. But the EMA advised no such age restrictions, leaving it up to its member-countries to decide whether to limit its use.

Several countries have already imposed limits on who can receive the vaccine, and any restrictions are closely watched since the vaccine, which is cheaper and easier to store than many others, is critical to global immunization campaigns and is a pillar of the U.N.-backed program known as COVAX that aims to get vaccines to some of the world’s poorest countries.

“This is a course correction, there’s no question about that,” Jonathan Van-Tam, England’s deputy chief medical officer, said during a press briefing. “But it is, in a sense, in medicine quite normal for physicians to alter their preferences for how patients are treated over time.”

Van-Tam said the effect on Britain’s vaccination timetable — one of the speediest in the world — should be “zero or negligible,” assuming the National Health Service receives expected deliveries of other vaccines, including those produced by Pfizer and Moderna.

EU and U.K. regulators held simultaneous press conferences Wednesday afternoon to announce the results of investigations into reports of blood clots that sparked concern about the rollout of the AstraZeneca vaccine.

The agency described the clots as “very rare” side effects. Dr Sabine Straus, chair of EMA’s Safety Committee, said the best data is coming from Germany where there is one report of the clots for every 100,000 doses given.

Medical staff prepares an AstraZeneca coronavirus vaccine during preparations at the vaccine center in Ebersberg near Munich, Germany.

the associated press