THE ESSENTIAL
- Currently, more than 53 million French people are fully vaccinated.
- In France, more than 38 million people have received their booster dose.
Four doses of vaccines against Covid-19 would increase the level of neutralizing antibodies, that is to say which block the viral infection in the cells, according to a study published on the medRxiv pre-publication site. But the researchers qualified this observation because the levels of antibodies reached with this fourth dose would not surpass those reached with the third dose. In other words, after the first booster shot, the following ones would only serve to find the post-booster antibody level, which drops over the months, but would not protect further. To reach this conclusion, the authors gathered 274 participants in a clinical trial. All were caregivers and received a fourth dose of messenger RNA vaccine (Pfizer-BioNTech or Moderna) at least three months after their booster shot.
Same protection against variants
In parallel, they isolated 25 of these participants in order to better understand the impact of a fourth dose on neutralizing antibodies against coronavirus variants. Thus, they observed the same results for the third and fourth doses: the neutralizing antibodies were more effective against Delta than against Omicron. Additional proof, according to the researchers, that a fourth dose would not offer a higher level of protection than with the initial booster whose level of protection is already very satisfactory.
A fourth dose for those over 75 and immunocompromised patients
The study participants were active people, which means that these results are valid for adults. On the other hand, for elderly patients, they could be different. Some countries, such as Chile or Great Britain, have already implemented a fourth dose for this category of the population. Across the Channel, people over 75 and individuals over 12 with comorbidities are invited to do so, for example. “People who are offered this fourth dose are those for whom the vaccine is probably least effective due to illness, immunosuppressive drugs or because of age. They are less likely to be as well protected with a vaccination and if infected they are more likely to be seriously ill, which is why these are the people who would benefit the most from a fourth dose.”explained Dr Peter English, former chairman of the British medical association’s Public Health Committee to the Science Media Center.
Currently in France, according to the recommendations of the Vaccine Strategy Orientation Council (COSV) in a review dated November 19, 2021, only immunocompromised people are affected by a fourth booster dose. In detail, these include, for example, patients with solid organ transplants and recent bone marrow transplants, suffering from autoimmune diseases, certain types of lymphoma or even rare forms of primary immune deficiency.