The Haute Autorité de Santé recommends a messenger RNA vaccine as a second injection for people under 55 who have received a first dose of AstraZeneca.
- The strategy of using two injections using a different technology for a vaccine is called heterologous prime-boost.
- Just over 500,000 people are affected.
- No study has been conducted on the effectiveness of this strategy, but the first data are “encouraging”, according to the HAS.
It’s a question of adjustment. On March 19, a few days after the suspension of the AstraZeneca vaccine, the High Authority for Health (HAS) pleaded in favor of the resumption of vaccination with this product for people over 55 years of age. But before this recommendation and the rise in cases of thrombosis, just over 500,000 people under the age of 55 had received a first dose of the AstraZeneca vaccine. What vaccine should be used for their second injection? In an opinion delivered this Friday, April 9the HAS decided and “recommends completing the vaccination schedule for this population with an mRNA vaccine within 12 weeks after the first injection.”
The heterologous prime-boost strategy
This HAS announcement follows that of Olivier Véran this Friday morning. “It is completely consistent to say that since the AstraZeneca vaccine is not recommended for people under 55 (…), if you have received a first injection and you are under 55, you will be offered a other vaccine”, he indicated on RTL. The 40-year-old Minister of Health is himself concerned since he received a dose of the British vaccine on February 8.
#AstraZeneca : the High Health Authority will recommend a 2nd dose of another vaccine for those under 55. “It’s totally logical”, according to @olivierveran – @VenturaAlba #RTLMatin ???????? pic.twitter.com/iEKbK88PqB
—RTL France (@RTLFrance) April 9, 2021
Using a different vaccine for the second injection may provide additional protection. “The strategy of resorting to a two-step vaccination scheme using for the second injection (boost) a vaccine using a different technique from the first (prime) is called ‘heterologous prime-boost’.specifies the HAS. Many arguments are in favor of this strategy, which has already been put to good use in the context of the development of certain vaccines (HIV in particular) and which has proven to be more effective than the homologous prime-boost approach (strictly identical injections) over the course of phase 1 and 2 studies in humans. It is also important to emphasize that the vaccines currently used or mainly under development in the anti-SARS-CoV-2 vaccination target the same antigen (protein S), which makes it possible to support this strategy..”
A follow-up study
For the moment, no study has been conducted on the effectiveness of this “heterologous prime-boost” strategy in the context of anti-SARS-CoV-2 vaccination. The HAS notes, however, that initial data has been revealed “encouraging”. She adds that she wants to set up a study “to evaluate in real life the immune response conferred by the mixed vaccination scheme”.
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