French body suggests mRNA dose after AstraZeneca jab

The French high authority of health suggested on Friday the “heterologous prime-boost” strategy for those younger than 55 who have had the AstraZeneca coronavirus jab to safeguard against thrombosis.

The High Authority of Sante (HAS) recommended “completing the vaccination schedule for this population with an mRNA vaccine-- COMIRNATY or Moderna-- within 12 weeks after the first injection.”

A single dose of the AstraZeneca vaccine is “insufficient to guarantee lasting effective protection,” against thromboembolic events, it noted in a statement.

The independent public authority of experts providing analyses, recommendations and measures for improvement in matters of health and medicine, said it based its suggestion on scientific rationale called “heterologous prime-boost.”

The strategy uses a two-step vaccination scheme: using a different technique from the first (prime) for the second injection (boost). Such techniques have been effective in HIV vaccines, it said.

It has recommended setting up a study to assess the immune response by the mixed vaccination schedule and monitoring those vaccinated with the first dose of the AstraZeneca and then those with an mRNA vaccine.

Last month, following reports of blood clots which led to a brief suspension of the AstraZeneca vaccine, HAS changed its recommendation to reserve the vaccine for people older than 55 years.

Since the rolling out of the AstraZeneca vaccine in February, more than 500,000 people in France who are younger than 55 were administered their first shot.

France resumed administration of the AstraZeneca vaccine shortly after the European Medicines Agency and the World Health Organization issued a green light.

President Emmanuel Macron once again backed AstraZeneca on Friday and said he trusts the recommendation of health authorities for its use in terms of ages.

"We do not use it for the youngest, but for the oldest we will continue ... especially when we have a risk factor," he was quoted by BFMTV during a visit to a pharmaceutical company in Eure-et-Loir.

In the coming weeks, he said that vaccination priority will be made for 70,000 professionals, mostly teachers and for care workers of the disabled and vulnerable.