Pfizer’s bivalent shot for COVID-19 has shown a potential link to stroke in people 65 and older, according to U.S. health officials citing preliminary data from one of several vaccine safety databases.

The potential risk with Pfizer’s vaccine was not seen in other safety databases, nor was it seen with Moderna’s COVID-19 vaccine, the officials said in a statement on the Food and Drug Administration’s website. The early finding still needs more investigation, and recommendations for the vaccine have not been changed, the statement said.

"When we find a signal we look for it in other parts of the system, which is what we’ve done (and will continue to do),” Kristen Nordlund, a spokesperson for the Centers for Disease Control and Prevention, said in an email.