September 24, 2021

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Four questions about the effectiveness of vaccines in months

The shields are less efficient than expected. According to a series of recently published scientific studies, key vaccines against Covit-19 have been falling in their safety levels for months. This observation has already led to the announcement of vaccine promotion campaigns for some countries, including Israel, the United States and France. Which vaccines are affected? What causes a weakened immune system? What are the possible solutions? Franinfo answers four questions raised by these studies.

1Do all vaccines lose their effectiveness?

Recent scientific studies seem to confirm this. Some studies, for example, of the delta variant, are associated with periods of high epidemic, not yet majority. Others do not differentiate between those who received only the first dose of the vaccine and those who were fully vaccinated. To determine the percentage of effectiveness of the vaccine, researchers generally calculate the risk of infection and infection. This analysis The Lancet (Link in English).

For messenger RNA vaccines, such as Moderna and Pfizer-Bioentech American Center for Disease Control and Prevention (CDC) estimates, In his last study (Link in English) Released on Tuesday, their coverage rate drops slightly over time, from 85% four months after vaccination to 73% five months later. But these averages, calculated since December 2020, are a general picture of the best.

The Astrogeneca vaccine, which protects against fewer infections than the Pfizer-Bioentech or Modern vaccines, is more resistant to time and delta variation than its competitors, according to a August 19 study. University of Oxford (co-developed with the Astrogenega vaccine). Analysis, It has not been reviewed yet, hopefully This vaccine protects 67% after one month, 65% after two months and 61% after three months. Four to five months after receiving both injections, against the condition provided protection Govit-19 Similar to the Pfizer-Bioentech vaccine, the study concludes.

This fall Johnson & Johnson’s single dose of Johnson vaccine may also be affected It is rarely used in France. According to Public Health France. A American University of New York Study (Link in English) Released in mid-July Actually points to a “Significant decrease” Efficacy of this vaccine against delta type. An observation shared in Hot Autoride de Sante France Underlines his site The Lack of data to ensure long-term performance “ Against this infectious variant of the Johnson vaccine.

2What causes this drop in performance?

The first factor was pointed out by scientists: the origin of the delta variant, very strong and conductive. The study, published by the US CDC, actually evaluates the effectiveness of the Pfizer-Bioendech and Modern vaccines. In the United States the delta variance has decreased from 91% to 66% since becoming the majority. Other studies conducted around the world confirm this weakness in the face of delta variation, although statistics vary from one study to another, according to vaccines. A worrying trend for many countries like France, this variation is often the majority.

In addition, vaccines seem to lose their effectiveness after a few months, as explained in the August 19 example. Review Natural (Article in English). A Study of Israeli physicians and researchers, More than 33,000 vaccinated people were vaccinated.Released in early August, estimates The chances of infection increase significantly from 146 days after complete vaccination. In France, Haute Autorité de santé (HAS) promises. This decline in vaccine efficacy is gradual and moderate over time. “, France Infori to its chairman Dominique Le Gluteck.

Important Note: This drop in the protection rate of vaccines is mainly felt in those over 60 years of age. “Immunity in the elderly decreases over time, France recalled Tuesday on Inter Jean-Paul Artis, President of the Federation of French Medical Associations. We know they produce fewer antibodies and the vaccine takes less.“The combination of these three factors (variation, time and age) helped establish the types of people at risk for the withdrawal campaign supporting HAS.

3Does this call into question the interest of the vaccine?

No, according to the scientists behind these studies. “LReduction of infections [par le Covid-19] The remaining two-thirds underscore the continued importance and benefits of the vaccine. “For example, the authors of a survey released Tuesday by the CDC in the United States commented. According to Dr. Goen Powells, who participated in the study on the astrogenic vaccine, there is a lack of protection. “Very light”And overall performance is not in question. “very high” Vaccines against severe forms of the disease.

View shared by US CDC released on Tuesday Another study (In English) Held for patients in Los Angeles from early May to late July. The survey shows that the network of federal agencies shows that those who are not vaccinated are almost 5 times more likely to be infected and 29 times more likely to be hospitalized than those who are not vaccinated.

4What are the solutions to this problem?

To counter this relative decline in performance, labs and health officials currently agree on one criterion: to organize a recall campaign. Despite reservations from the World Health Organization in this regard, many countries are already planning to inject additional doses in the coming weeks. In France, HAS on Tuesday reviewed the policy of the government’s desired withdrawal campaign and should begin this fall. The head of HAS says the campaign worries people over the age of 65 who are currently only using messenger RNA vaccines and are considered at risk, i.e. at least 15 million people in France.

In the long run, renewal of vaccines may be considered, but only if a new variant justifies it, explained Ukhur Sahin, co-founder and director of Bioendech in early August. “In three or six months, if another variant dominates, the decision will now be wrong.”, As mentioned later The owner of the German laboratory considers the booster size to be adequate security.

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