Four questions about vaccine efficacy declining over months

2What caused this decrease in efficiency?

Scientists pointed to the first factor: the emergence of a delta variant, more powerful and transmissible. The study already published by the US Centers for Disease Control and Prevention estimates the effectiveness of the Pfizer-BioNTech and Moderna . vaccines It has fallen from 91% to 66% since the delta variant became the majority in the United States. Other surveys conducted around the world confirm this weakness in the face of the delta variant, even if the numbers differ from study to study, and depending on vaccines. A worrying trend for many countries such as France, where this alternative is by far the majority.

In addition, it has been observed that vaccines seem to lose their effectiveness after a few months, as we demonstrated for example on August 19. reconsidering temper nature (article in English). a A study by Israeli doctors and researchersAnd conducted on more than 33,000 vaccinated people,Published in early August, it is estimated that The probability of infection increases significantly from 146 days after full vaccination. In France, the Haute Autorité de santé (HAS) is reassuring. “This decrease in vaccine efficacy is gradual and moderate over time.”, confirmed to franceinfo its president, Dominique Le Golodic.

Important note: This decrease in the rate of protection from vaccinations is mainly felt in people over 60 years of age. “Immunity decreases over time in the elderly, Tuesday called in France Inter Jean-Paul Ortiz, President of the Confederation of French Medical Syndicates. We know that they make fewer antibodies, and that the vaccine takes less.“It is the combination of these three factors (difference, time, and age) that has significantly enabled HAS to create categories of the population at risk for the recall campaign it advocates.

3Does this call into question the interest of vaccination?

No, according to the scientists behind these studies. “lamreduce inflammation [par le Covid-19] The remaining two-thirds confirm the continued importance and usefulness of vaccination., for example commented the authors of the survey published Tuesday by the US Centers for Disease Control. For Dr. Quinn Boyles, who was involved in the AstraZeneca vaccine study, the notable decrease in protection remains “very light”and does not in any way call into question its overall efficacy.”very high” Vaccines against severe forms of the disease.

A view shared by the US CDC, which was published on Tuesday Another study (in English) Performed on patients in Los Angeles from early May to late July. In this survey, the Network of Federal Agencies showed that unvaccinated people were about 5 times more likely to become infected and 29 times more likely to be hospitalized than those who were vaccinated.

4What are the solutions to this problem?

To counteract this relative decline in efficiency, laboratories and health authorities are currently agreeing on one measure: to organize a recall campaign. Despite the WHO’s reservations on the subject, several countries have already planned to inject an additional dose of the vaccine in the coming weeks. In France, HAS on Tuesday ratified the principle of the government’s desired no-confidence campaign that should begin this fall. This campaign, which will only use messenger RNA vaccines, currently concerns those over 65 as well as those considered at risk, that is, at least 15 million people in France, according to the head of HAS.

In the long term, a vaccine update could be considered, but only if a new alternative justifies it, Ugur Sahin, co-founder and director of BioNTech, explained in early August. “A decision now may turn out to be a mistake if another formula prevails in three or six months”, then the specified The head of the German laboratory who considers the booster dose adequate protection.