large study of 22 million people proves the effectiveness of vaccines

The largest study conducted worldwide to date, covering 22 million people over the age of 50, concludes that all Covid-19 vaccines are highly effective and reduce the risk of severe forms of Covid-19 and death. However, this French study, conducted by Epi-Phare, does not say to what extent vaccines prevent infection and transmission of Covid-19.

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The vaccination against Covid-19 reduced by 90% the risk of hospitalization and death in people over 50 and also seems effective against the Delta variant, on which we still lack perspective, according to a large French study involving 22 million of people. “People vaccinated are 9 times less likely to be hospitalized or dying from Covid-19 than unvaccinated people“, Explains to AFP the epidemiologist Mahmoud Zureik, director of the Epi-Phare structure, which associates the Health Insurance (Cnam) and the Medicines Agency (ANSM). These data confirm other observations made in real life in other countries, Israel, United Kingdom or United States. Corn French study is ” the largest conducted in the world », According to Professor Zureik.

Epi-Phare researchers compared the data of 11 million vaccinated people over 50 years old with those of 11 million unvaccinated people in the same age group, over a period from December 27, 2020 (start vaccination in France) on July 20. From the 14e day after the injection of the second dose, the researchers observed ” a reduction in the risk of hospitalization greater than 90% “.

The Delta variant always questions

To identify the impact of Delta variant, now dominant, the researchers specifically estimated the reduction in the risk of hospitalization during the period when it gained momentum in France, from June 20, so a month before the end of the ‘study. They found results comparable to previous periods: a efficiency 84% among those aged 75 and over, and 92% among those aged 50-74. This makes it possible to provide “ first elements, [mais] this period remains very short to assess the real impact of vaccination on this variant (…). The study must be continued to integrate the data for August and September, ”underlines Professor Zureik.

This observation on the effectiveness of vaccines applies to those of Pfizer / BioNtech, Moderna and AstraZeneca – the fourth authorized in France, that of Janssen, was later authorized, was used in smaller proportions and is therefore not included in the study. ” This reduction is the same magnitude for the risk of death during hospitalization for Covid-19 », According to Epi-Phare. In addition, the effectiveness on severe forms of the disease ” does not appear to decrease over the available follow-up period, which was up to 5 months “.

A study by couples

The study has two parts, devoted to two distinct populations. On the one hand, those aged 75 and over, with a sample of 7.2 million people (50% vaccinated and 50% non-vaccinated). On the other hand, 50-74 year olds, with a sample of 15.4 million people (50% vaccinated and 50% non-vaccinated).

Avoiding severe forms is the major public health objective. An epidemic without serious form is no longer an epidemic

The vaccination campaign in France began on December 27, 2020 for the former, and on February 19 for the latter (February 19 for those aged 65 to 74 and May 10 for those aged 50 to 64). The study followed these two populations until July 20 (with similar efficacy results in both age groups).

To compare the data, the researchers formed pairs. For each person vaccinated on a given date, they matched an unvaccinated person of the same age, same sex and living in the same region. They followed these couples until July 20 and compared the rates hospitalization.

This study door only on the effectiveness of vaccines against severe forms. It does not allow to say how well they prevent being infected and transmitting Covid-19. Other work around the world has shown that, compared to other variants, Delta lowered the effectiveness of vaccines against infection. However, avoiding severe forms is “ the major public health objective “, Underlines Professor Zureik:” An epidemic without serious form is no longer an epidemic “.

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