Germany suspended the routine use of Oxford-AstraZeneca Covid-19 vaccine for people aged below 60 because of a risk of rare blood clots.
The German medicines regulator found 31 cases of a type of rare blood clot among the nearly 2.7 million people who had received the vaccine in Germany.
Almost all the cases are reportedly in younger and middle-aged women.
People under 60 can still receive the jab but only “at the discretion of doctors, and after individual risk analysis and thorough explanation”, according to a document.
Canada earlier suspended use of the AstraZeneca jab in people under 55.
AstraZeneca said international regulators had found the benefits of its jab outweighed risks significantly.
It said it was continuing to analyse its database to understand “whether these very rare cases of blood clots associated with thrombocytopenia occur any more commonly than would be expected naturally in a population of millions of people”.
“We will continue to work with German authorities to address any questions they may have,” it added.
The EU and UK medicine regulators both backed the vaccine after previous cautionary suspensions in Europe this month.
The European Medicines Agency (EMA) and the UK Medicines & Healthcare products Regulatory Agency stressed that the benefits of the AstraZeneca vaccine continued to outweigh the risk of side effects.
AstraZeneca’s product is one of the most widely used coronavirus vaccines in the West, and is meant to be supplied on a not-for-profit basis to the developing world.
The EU’s rollout of its vaccination programme has been dogged by delays because of delivery and production problems, and Germany is among several states now fearing a third wave of infections.