A French study, published on Tuesday, confirms the efficacy of booster vaccines against severe forms of covid-19, including its latest variants and subvariants. However, it shows that this efficacy decreases rapidly after the injection of the booster dose.
The booster doses made it possible to strengthen protection against the risk of hospitalization, but that protection was limited in time”, concludes the report by the National Agency for Medicines Safety (ANSM) and Health Insurance.
This study, which has not yet been published in a scientific journal, is the latest episode in a series of studies that have looked at the efficacy of covid vaccines since their introduction in early 2021.
The study fills a data gap.
Anti-Covid vaccination, which in France is essentially based on Moderna and Pfizer/BioNTech vaccines, has proven effective against severe forms, although it does not reduce the risk of contamination in the medium or long term.
However, even in the face of hospitalizations, effectiveness tends to wane over time, prompting health authorities to organize recall campaigns, known as third, fourth, and then fifth doses.
However, data on the actual benefits of these successive enhancements was lacking, particularly after the appearance of the Omicron variant. The latter, which has known several incarnations, more easily escapes the immune response.
The study published this Tuesday -carried out under the direction of epidemiologist Mahmoud Zureik- analyzed the case of patients hospitalized with Covid between June and October 2022. The researchers compared their vaccination status with that of a group of people who have not been hospitalized, the called the case control procedure.
Orientation of vaccination campaigns
First, it shows that the vaccines have maintained good efficacy against the risk of hospitalization, even against Omicron. This is the case for people who have only received their first two doses, but this protection is further increased with boosters: efficacy against hospitalizations is estimated at 45% after a primary vaccination, 56% for a third dose and 75% after a fourth or fifth dose.
But the effect of these reminders quickly diminishes over time. After six months, there is little difference compared to people who have only received a vaccine.
These results therefore imply adequately targeting vaccination campaigns in relation to waves of Covid, a difficulty increased by the fact that they are much more frequent and irregular than, for example, seasonal flu.
Source: BFM TV
