Dynamics of the Delta variant in France

The Pasteur Institute hypothesizes in this study that there is no change in the transmissibility of the Delta variant related to climate during the study period (June 15 to October 1)


If the growth momentum of the Delta variant continues at the same pace in the coming weeks, the study results suggest that the pressure on the hospital could be significant as early as August, at a time when hospitals may be struggling to accommodate a large influx of patients.

Even a relatively small reduction in the infection rate this summer (on the order of 10-25%) would significantly reduce the magnitude of the peak in hospital admissions and delay the onset of the peak to a time when the hospital would be in a better position to absorb an influx of patients.

Description of the Study:

  • Title: Dynamique du variant Delta en France métropolitaine.
  • Principal Investigators: Researchers of the Mathematical Modeling of Infectious Diseases unit of the Pasteur Institute.
  • Centre of implementation: Pasteur Institute.
  • Study Population: Screening data documenting the L452R mutation in France.
  • Methods: Two different approaches are used to anticipate the dynamics of cases and hospitalizations in the coming weeks. A simple exponential growth model, and a more sophisticated mathematical model that takes into account natural and vaccine immunity, future increase in vaccine coverage, as well as transmission dynamics and risks by age group.

Objectives of the Study:

Principal Objectives: To study the propagation dynamics of the Delta variant by analyzing detection data documenting the L452R mutation.

More about this Study:

Scientific context: In the regions of metropolitan France (excluding Corsica), the Delta variant is growing rapidly, with an estimated regional effective number of Rd between 1.5 and 2.8 from June 15 to July 5. This means that in the regions it currently takes between 3.5 and 10.4 days to double the number of Delta cases. Estimates of RoI by region may still be uncertain due to relatively low incidences and the limited time frame.


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