Shares in Moderna and Pfizer sank on Wednesday after the European Union drug regulator said it was looking into possible new side effects of the companies' COVID-19 vaccines.
That includes kidney inflammation, an allergic skin reaction, and a renal disorder with heavy protein loss in urine.
Pfizer is by far the biggest supplier of COVID-19 vaccines to the European Union, issuing just over 330 million doses in the region compared to some 43 million from Moderna.
Both companies did not immediately respond to Reuters requests for comment.
The European Medicines Agency (EMA) has not recommended any changes to the vaccine labels.
It says the latest assessment is part of routine updates to the safety section of the authorized vaccines database.
It's also looking into menstrual disorders as a possible side effect of vaccines, including those from AstraZeneca and Johnson & Johnson.
Last month, the EMA found a possible link between very rare heart inflammation and Pfizer and Moderna's vaccines, which use mRNA technology.
However, the European regulator and the World Health Organization have stressed that benefits from these vaccines outweigh any risks.
The watchdog did not give details on Wednesday on how many cases of the new side effects were recorded, but said it's requested more data from both companies.