PARIS (Reuters) – France’s top health organization will say on Friday that recipients of a first dose of AstraZeneca’s traditional COVID-19 vaccine under the age of 55 should receive a second injection of a new messenger RNA vaccine, two sources who are aware of the plans said Thursday.
Reuters had reported on Wednesday that the Haute Autorite de la Sante (HAS), which is responsible for outlining how to use vaccines approved by the European Medicines Agency (EMA) in France, is considering this possibility.
The HAS has now decided to go ahead with the plan, the two sources said. Two mRNA vaccines, one from Pfizer and BioNTech and one from Moderna, have been approved for use in France.
Messenger RNA vaccines prompt the human body to make a protein that mimics part of the virus, triggering an immune response, while viral vector vaccines like those from AstraZeneca use a cold virus to carry DNA instructions to do the same.
A spokeswoman for HAS did not comment.
Vaccination programs have stuttered in Europe and elsewhere over the past month as a very small number, mostly young recipients of the AstraZeneca injection, were found to have contracted extremely unusual blood clots, leading some countries to discontinue their use as a precaution.
Most have resumed recording, although some have done so with age restrictions.
In France, the HAS advised on March 19 that only people 55 and older should receive the AstraZeneca vaccine, which had already been given to 500,000 people as the first dose.
Although the numbers are small compared to the tens of millions vaccinated in the EU, a decision to give another booster injection would be significant because the approach has not been tested in late-stage human trials.
Germany was the first European country to recommend that people under 60 who have had a first AstraZeneca injection should be given a different product for their second dose.
Some experts say that because all vaccines target the same external “peak” protein of the virus, they can be complementary. But there is no evidence that this approach will be equally effective.