French study of over 22m people finds vaccines cut severe Covid risk by 90%
Largest study of its kind also finds vaccines appear to protect against worst effects of Delta variant
Researchers compared 11m vaccinated over-50s with the same number of unvaccinated from the same age group between 27 December 2020 and 20 July. Photograph: Murdo MacLeod/The Guardian
Vaccination reduces the risk of dying or being hospitalised with Covid-19 by 90%, a French study of 22.6 million people over the age of 50 has found.
The research published on Monday also found that vaccines appear to protect against the worst effects of the most prevalent virus strain, the Delta variant.
“This means that those who are vaccinated are nine times less at risk of being hospitalised or dying from Covid-19 than those who have not been vaccinated,” the epidemiologist Mahmoud Zureik, who oversaw the research, told Agence France-Presse.
The study – the largest of its kind so far – was carried out by Epi-Phare a scientific group set up by France’s health system, its national health insurance fund, l’Assurance Maladie (CNAM), and the country’s ANSM medicines agency.
Researchers compared 11.3 million vaccinated over-50s with the same number of unvaccinated from the same age group between 27 December 2020, when vaccinations began in France, and 20 July this year.
They found “a reduction in the risk of hospitalisation superior to 90%” from the 14th day after the second dose and a similar reduction in the number of deaths from Covid-19. Similar findings have previously been published in Israel, the UK and the US.
The vaccines’ effectiveness in combatting the most serious symptoms of Covid did not diminish during the five-month period of the study, they said. The results were the same no matter whether the patient was given the Pfizer/BioNTech, Moderna or Oxford/AstraZeneca vaccine.
The Janssen one-dose shot, authorised later in France, was not included as the researchers felt there had not been enough patients or time to properly study its effectiveness.
Researchers only had a month between the emergence of the Delta variant in France and the end of the study, but results showed the vaccines reduced the risk of serious symptoms and death by 84% among the over-75s and 92% for the 50-74 age group.
“This is a very short period to evaluate the real impact of the vaccination on this variant,” Zureik said, adding that research was continuing into the effect of vaccines on the Delta variant.
To ensure the closest possible comparison, researchers paired vaccinated and unvaccinated people of the same age and sex living in the same region. The study looked only at the most serious symptoms of infection and did not examine if the vaccines stopped people becoming infected or transmitting the virus.
Zureik said avoiding the most serious infections was “the main public health objective”. “An epidemic without serious infections is no longer an epidemic,” he added.
The report concludes: “All the vaccines [studied] against Covid-19 are highly effective and have a major effect on the reductions of serious forms of Covid-19 among people aged 50 years and older living at the current time in France. The continuing research by Epi-Phare will allow us to measure the evolution of this effectiveness over a longer period and better establish the effects on the Delta variant.”
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