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Original Research ARTICLE

Front. Med. | doi: 10.3389/fmed.2020.00274

Impact of lockdown on the epidemic dynamics of COVID-19 in France Provisionally accepted The final, formatted version of the article will be published soon. Notify me

 Lionel Roques1*, Etienne K. Klein1, Julien Papaix1,  Antoine Sar2 and Samuel Soubeyrand1
  • 1Institut National de la Recherche Agronomique (INRA), France
  • 2Medicentre Moutier SA, Switzerland

The COVID-19 epidemic was reported in the Hubei province in China in December 2019 and then spread around the world reaching the pandemic stage at the beginning of March 2020. Since then, several countries went into lockdown. Using a mechanistic-statistical formalism, we estimate the effect of the lockdown in France on the contact rate and the effective reproduction number Re of the COVID-19. We obtain a reduction by a factor 7 (Re=0.47, 95%-CI: 0.45-0.50), compared to the estimates carried out in France at the early stage of the epidemic. We also estimate the fraction of the population that would be infected by the beginning of May, at the official date at which the lockdown should be relaxed. We find a fraction of 3.7% (95%-CI: 3.0-4.8%) of the total French population, without taking into account the number of recovered individuals before April 1st, which is not known. This proportion is seemingly too low to reach herd immunity. Thus, even if the lockdown strongly mitigated the first epidemic wave, keeping a low value of Re is crucial to avoid an uncontrolled second wave (initiated with much more infectious cases than the first wave) and to hence avoid the saturation of hospital facilities.

Keywords: COVID 19, LockDown, Effective reproduction number, Bayesian inference, Mechanistic-statistical model, Herd immunity, SIR (SIRD) model

Received: 27 Apr 2020; Accepted: 18 May 2020.

Copyright: © 2020 Roques, Klein, Papaix, Sar and Soubeyrand. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Lionel Roques, Institut National de la Recherche Agronomique (INRA), Paris, France,