Nearly a dozen countries resumed use of AstraZeneca’s COVID-19 vaccine on Friday as EU and British regulators said the benefits of immunisation outweighed any risks.

Many governments had temporarily paused inoculations, citing an abundance of caution while they waited for health regulators to investigate reports of rare blood clotting in people who had received the AstraZeneca vaccine.

The European Medicines Agency (EMA) came to what it called a “clear” conclusion that the vaccine’s benefits in protecting people from coronavirus-related death or hospitalization outweighed the possible risks, though the watchdog did not definitively rule out a link between the inoculations and the unusual blood disorders.

In general, common side effects from vaccines include those that affect the injection area, such as pain, redness or swelling, and those that affect the rest of the body, like fatigue, headache, muscle pain, chills, fever or nausea. These are usually normal signs that the vaccine is working as the body is building protection.

The EMA review covered 20 million people given the AstraZeneca vaccine in the United Kingdom and the European Economic Area (EEA). It followed reports of about 30 cases of rare brain blood clots.

The EMA said it would update its guidance on the vaccine to include an explanation for patients about the potential risks and information for healthcare professionals, to help people recognise instances when they may need to seek medical assistance following a vaccination.

Although AstraZeneca’s vaccine is the focus of recent attention, other illnesses have also been occasionally observed following the use of vaccines by other drug makers. More research is needed to determine whether there is a link between those conditions and the vaccines – experts say the number of cases seen so far could be in line with background rates in the general population with or without vaccination.