The British government on Wednesday recommended that people under the age of 30 should not receive shots of AstraZeneca’s COVID-19 vaccine, after a European drug regulator described a “possible link” between the vaccine and rare cases of blood clots. Other countries have scaled back use of the vaccine in people under 60. About one in 100,000 recipients of AstraZeneca’s vaccine have reported clotting — 18 cases of which have been fatal. European regulators noted that blood clots are often a symptom of COVID-19, and said the benefits of AstraZeneca’s vaccine continue to far outweigh the risks.

This comes as a new study found more than one out of three survivors of severe COVID-19 developed psychiatric or neurological conditions within six months of their infection.