The results show that this two-dose vaccination regimen provides 88% protection against the original strain of the virus, 86% against the Alpha variant, and 77% against the Beta variant. These findings were published on July 14, 2021, in *The Lancet Regional Health Europe*.

In late 2020, two new variants of SARS-CoV-2 emerged. At that time, England experienced a resurgence in SARS-CoV-2 infection rates attributed to the emergence of the Alpha variant, a variant with higher transmissibility than the original SARS-CoV-2 strain. This event was accompanied by the emergence of the Beta variant in South Africa, whose E484K mutation is associated with immune escape. The emergence of these different SARS-CoV-2 variants coincided with the start of mass vaccination campaigns worldwide. In this context, it was therefore necessary to analyze the efficacy¹ of available mRNA vaccines against these different SARS-CoV-2 variants.

At the same time, since October 2020, the Pasteur Institute, in collaboration with the French National Health Insurance Fund (Caisse nationale de l’Assurance Maladie), Ipsos, and Santé publique France, has launched the ComCor study, a nationwide case-control study analyzing the sociodemographic factors, behaviors, and practices associated with SARS-CoV-2 infection. The results of the first phase of this study were published in The Lancet Regional Health on June 7, 2021.

In February 2021, researchers adapted the questionnaire to include information on COVID-19 vaccination, prior SARS-CoV-2 infections, and the nature of the variants responsible for infection. This information was used to assess the efficacy of two doses of mRNA vaccines against the alpha and beta variants circulating in France, and to evaluate the protection provided by prior SARS-CoV-2 infections. All infected individuals were invited to participate in the survey by the National Health Insurance Fund.

The analysis included 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 between February and May 2021. Through this study, researchers demonstrated that two doses of the mRNA vaccine provide (seven days after the second dose) 88% (81–92) efficacy against the original virus, 86% (81–90) against the Alpha variant, and 77% (71–90) against the Beta variant. No difference in vaccine efficacy was observed based on age, sex, or occupational exposure.

Another important finding of this study concerns a history of SARS-CoV-2 infection. The researchers show that a recent infection (2 to 6 months ago) confers protection similar to that observed with mRNA vaccines, but that this protection wanes after six months.

These analyses will now be expanded to estimate vaccine efficacy against the Delta variant, which has become the dominant strain in France since early July.

For more information:

• More information on the overall methodology of the Comcor study: click here

• Read the December 17, 2020 press release "ComCor Study on SARS-CoV-2 Transmission Sites: Where Are the French Getting Infected?"

The ComCor project is funded by REACTing, the Fondation de France as part of the “Tous unis contre le virus” alliance, and the Institut Pasteur. It recently received the Capnet “national research priority” designation.

Source

Impact of original, B.1.1.7, and B.1.351/P.1 SARS-CoV-2 lineages on vaccine effectiveness of two doses of COVID-19 mRNA vaccines: Results from a nationwide case-control study in France, Lancet Regional Health Europe, July 14, 2021

Tiffany Charmet¹, Laura Schaeffer¹, Rebecca Grant^1,2, Simon Galmiche¹, Olivia Chény³, Cassandre Von Platen³, Alexandra Maurizot⁴, Alexandra Rogoff⁴, Faïza Omar⁵, Christophe David⁵, Alexandra Septfons⁶, Simon Cauchemez⁷, Alexandre Gaymard^8,9, Bruno Lina^8,9, Louise H Lefrancois^10,11, Vincent Enouf^10,11,12, Sylvie van der Werf^10,11, Alexandra Mailles⁶, Daniel Levy-Bruhl⁶, Fabrice Carrat¹³, Arnaud Fontanet^1,14

¹ Institut Pasteur, Emerging Diseases Epidemiology Unit, Paris, France
² Sorbonne University, Paris, France
³ Institut Pasteur, Centre for Translational Research, Paris, France
⁴ Caisse nationale de l’Assurance Maladie, Paris, France
⁵ Institut IPSOS, Paris, France
⁶ Santé publique France, Saint-Maurice, France
⁷ Institut Pasteur, Mathematical Modelling of Infectious Diseases Unit; UMR2000; CNRS, Paris, France
⁸ CNR for Respiratory Infection Viruses, Institute of Infectious Agents, Hospices Civils de Lyon
⁹ Virpath, International Center for Infectious Disease Research, University of Lyon, Inserm U1111, CNRS UMR5308, École Normale Supérieure de Lyon, UCBL, Lyon, France
¹⁰ Molecular Genetics of RNA Viruses, Department of Virology, Institut Pasteur CNRS UMR 3569; University of Paris, Paris, France
¹¹ National Reference Center for Respiratory Viruses, Institut Pasteur, Paris, France
¹² Mutualized Platform of Microbiology, Pasteur International Bioresources Network, Institut Pasteur, Paris, France
¹³ Sorbonne University, Inserm, IPLESP, Saint-Antoine Hospital, APHP, 27 rue Chaligny, Paris F75571
¹⁴ Conservatoire national des arts et métiers, PACRI Unit, Paris, France