In the past six months, the World Health Organization has classified four variants of SARS-CoV-2 as “of concern” because they are more transmissible or may elude the immune response. They have been called the Alpha, Beta, Gamma, and Delta variants.
At the end of 2020, two new variants of SARS-CoV-2 were reported in the UK and South Africa respectively. This came at a time when the UK was experiencing a resurgence in the incidence of SARS-CoV-2 infections. This was later attributed to the emergence of the Alpha variant, which has now demonstrated increased transmissibility compared to the original SARS-CoV-2. The beta variant was first reported in South Africa and later identified as carrying a mutation known as E484K which is associated with immune evasion. The declaration of the first variants of SARS-CoV-2 came as mass vaccination campaigns against COVID-19 began globally. In France, Alpha and Beta were both circulating during the first months of 2021. It was therefore important to analyze the effectiveness of COVID-19 messenger RNA (mRNA) vaccines against these worrying variants of SARS-CoV-2.
In October 2020, the Institut Pasteur, in collaboration with the National Health Insurance Fund (CNAM), Ipsos and Public Health France, launched the ComCor study, a national case-control study to analyze socio-demographic factors, behaviors and practices associated with SARS-CoV-2 infection. All people infected with SARS-CoV-2 were invited to participate in the study by the CNAM, while uninfected controls were identified via a representative panel of Ipsos. The first results of the study were published in Lancet Regional Health June 7, 2021.
In February 2021, scientists adapted the ComCor questionnaire to add information on vaccination against COVID-19, a previous infection with SARS-CoV-2 and information on the variants responsible for the infection, provided as part test results. This information was used to assess the efficacy of two doses of mRNA vaccine against the Alpha and Beta variants, and to assess the protection conferred by a previous infection with SARS-CoV-2.
In this study, 7,288 people infected with the original strain, 31,313 people infected with the Alpha variant, 2,550 people infected with the Beta variant and 3,644 uninfected controls were included between February and May 2021. The study allowed scientists to demonstrate that two doses of mRNA vaccine conferred 88% (81-92) efficacy against infection with the original virus, 86% (81-90) efficacy against infection with the Alpha variant and 77% (71-90) efficacy against beta variant infection, as measured seven days after the second dose. No difference in vaccine efficacy was found between different categories of age, sex or occupational exposure.
“There was a lot of expectation regarding the results (of vaccine efficacy) for the beta variant, known for its E484K mutation associated with immune evasion. Our estimate of 77% protection is very close to the estimate of 75% reached by the only other study in the world to evaluate the effectiveness of mRNA vaccines against this variant. These analyzes confirm the effectiveness of COVID-19 vaccines and the key role they have to play in the fight against the epidemic, ”explains Arnaud Fontanet, head of the epidemiology of emerging diseases unit at the Institut Pasteur and professor at the National Conservatory of Arts and Crafts (CNAM).
Another important finding of the study was linked to a previous infection with SARS-CoV-2. Scientists have shown that recent infection (within the last 2-6 months) confers protection similar to that seen with mRNA vaccines.
The analyzes will now be extended to estimate the efficacy of the vaccine against the Delta variant, which has been the dominant variant in France since early July 2021.
The ComCor project is funded by REACTing, the Fondation de France via the alliance “All united against the coronavirus”, and the Institut Pasteur. It has just been labeled CAPNET “national research priority”.
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