France's medical regulator approved the resumed use of AstraZeneca's COVID-19 vaccine on Friday, but said it should only be given to people aged 55 and older.

France was one of more than a dozen European Union states that suspended use of the Anglo-Swedish vaccine this week following reports of blood clotting in a small number of recipients of the shot.

The EU's drug watchdog (EMA) on Thursday said it was convinced the benefits of the AstraZeneca vaccine outweighed the risks.

The recommendation from the National Authority for Health (HAS) reflected signs that the blood-clotting affected younger people mostly, whose risk of dying from COVID-19 was lower than the elderly.

"Given the data provided by the EMA, it is the HAS's belief that vaccination with the AstraZeneca vaccine can resume immediately," said the French regulator in a statement.

"However, the EMA has identified a possible increased risk of (thrombosis) in people under 55 years old. The HAS recommends using the AstraZeneca vaccine at this stage only for people aged 55 and over, who represent the majority of priority people."

Guidance would be given soon to those under 55 who have already received a first dose of AstraZeneca, the HAS said.

When France first approved use of the AstraZeneca shot in early February, it said it should be only for under 65s, with President Emmanuel Macron calling it "quasi-ineffective" for anyone beyond their mid-60s.

France only removed that restriction earlier this month.