France's public health authority has recommended people under 30 be given Pfizer's Comirnaty Covid-19 vaccine when available instead of Moderna Inc's Spikevax jab, which carried comparatively higher risks of heart-related problems.
The Haute Autorite de Sante (HAS), which does not have legal power to ban or licence drugs but acts as an advisor to the French health sector, cited "very rare" risks linked to Myocarditis, a heart disease, that had shown up in recent data on the Moderna vaccine and in a French study published on Monday.
"Within the population aged under 30, this risk appears to be around five times lesser with Pfizer's Comirnaty jab compared to Moderna's Spikevax jab," HAS said in its opinion published on Monday.
HAS said that its recommendation, which would apply regardless of the vaccine's use as a first, second or third "booster" dose, would be valid until more scientific findings on the matter are known.
For persons aged over 30, however, the authority explicitly recommended the use of the Moderna vaccine, saying its effectiveness was slightly superior.
The European Union's drug regulator last month approved Moderna's booster vaccine, saying in its review that the jab may be given to people aged 18 years and above, at least six months after the second dose.