Faced with the progression of the Omicron variant, the High Authority for Health (HAS) is tightening the mesh of the vaccine net. In a notice published on Friday, December 24, the high authority paves the way for the administration of the booster dose from three months after the full vaccination schedule, instead of the five months it took so far. At the same time, it recommends the administration of this booster dose to children 12 to 17 years old with pathological or drug-induced immunodeficiency, or comorbidities that increase the likelihood of developing severe forms of Covid-19.
The HAS bases its opinion on data acquired in « real life », in particular in the United Kingdom, in Israel and in France, but also on work of modeling. British studies – not yet formally published – suggest in particular that Pfizer’s vaccine maintains, for the two months following the second dose, protection of the order of 80% against the non-severe symptomatic forms caused by the Omicron variant.
But the same work also suggests a drop in this rate of protection to around 34% from the fourth month, and a rise to around 75% as soon as two weeks after the third dose. Cautious, the HAS notes that the duration of this level of protection is to date unknown.
The unvaccinated over-represented in the hospital
To establish its recommendation, the authority also relies on the projections of the Pasteur Institute. This work on modeling the effects of different vaccine strategies indicates that an increase in the rate of administration of the third dose – 1.2 million injections per day, instead of the 800,000 daily at the time of writing of the opinion. – could be able « Reduce the size of the peak hospitalizations between 9% and 17% ».
The data collected from the Department of Research, Studies, Evaluation and Statistics (DREES) provide an idea of the decrease, over time, in the level of protection offered by vaccination against the Delta variant. . Between mid-October and mid-November, « For people with a complete regimen for six months or more, protection against serious forms (conventional hospitalizations in critical care) decreases to around 80%, losing around 10 points for those aged 60 to 80 », considers the HAS in its opinion. At six months after the second dose, this protection loses between 5 and 10 points for those over 80, compared to the protection conferred at three months, according to the same data.
Raw data from DREES circulates intensely on the Web, where it is subject to various interpretations. The HAS recalls in its opinion that despite the decline in vaccine effectiveness over time and the appearance of new variants, people who have not completed their vaccination schedule remain over-represented among the sick and dead from Covid-19. . Between early November and early December, the unvaccinated only represented 9% of the French population aged 20 and over, but they accounted for 41% of hospitalizations, 52% of critical care admissions and 38% of deaths.