France will give the Pfizer/BioNTech or Moderna vaccine as a second dose to people aged under 55 who have already received a first dose of the Oxford/AstraZeneca jab, as part of its response to concerns about rare blood clotting incidents.
The decision was announced on Friday after a recommendation from the Haute Autorité de Santé, a panel of medical experts who advise the government.
It will affect roughly 500,000 people under 55 who were given a first shot of AstraZeneca from early February to mid-March when they were eligible under the country’s strategy at the time of giving health care workers the vaccine. Other jabs were reserved for the elderly.
When the blood clot concerns emerged, France changed course to use AstraZeneca vaccine only for people aged above 55. Nothing will change for this group, said the HAS.
“Given that the protection of the Covid-19 vaccines begins to diminish after three months, these people need an additional dose,” said Élisabeth Bouvet, a vaccine expert and member of the HAS.
At a press conference, the HAS recognized that the dose-mixing approach was not yet common or supported by large-scale clinical evidence, and called for additional studies to be carried out.
In a statement, the HAS said that all the Covid-19 vaccines were aimed at the same spike protein “which supports this strategy”, as well as referring to early-stage, experimental trials in vaccines against HIV which use boosters that are different to the first shot.
Even without clinical data to back the mixed-dose approach, Bouvet said that they believed it carried low risks of side effects and was likely to offer people sufficient protection.
Health minister Olivier Veran told RTL radio on Friday that the approach was “totally logical” given European regulators’ analysis of the rare blood clotting side effect, and France’s adoption of an age restriction as a result.