Phase 3 clinical trials of the Pfizer coronavirus vaccine showed no links to cardiovascular problems.

But more research is needed to confirm heart and circulatory safety in people who were not well represented in those studies, including older seniors.

Almost a year ago, Pfizer's SARS-CoV-2 vaccine became the first to receive emergency use authorization.

It remains the most widely-used coronavirus vaccine in many countries, including France.

A study of people ages 75 and older admitted to French hospitals finds no increase in heart attacks, strokes or breathing problems caused by blood clots or blockages in the two weeks after each vaccine dose.

The findings, published in the journal JAMA, are consistent with studies in the U.S. and Israel of those conditions during the 42 days and 21 days following vaccination.

The authors call for more research in under-studied populations.