SARS-CoV-2 in Partially Vaccinated Populations

This study aims to study how partial vaccination of the French population should change the epidemiology of SARS-CoV-2 and to determine the implications for epidemic control


– In the scenario characterised by 30%-70%-90% vaccination coverage among 12-17, 18-59 and ≥60 years old, a significant strain on health care is expected in the absence of measures.
– Unvaccinated individuals contribute 12 times more to transmission than vaccinated individuals.
– Unvaccinated adults ≥60 years account for 3% of the population, but 36% of hospitalisations.
– Given limited coverage, children aged 0-17 years account for about half of infections and disease transmitters.
– Non-pharmaceutical measures have a similar impact whether applied to all individuals or only to the unvaccinated.
– Of all the interventions considered, including repeated testing and non-pharmaceutical measures, vaccination of the unvaccinated is the most effective. Vaccination of children is important to protect them from the harmful effects of non-pharmaceutical measures.

Description of the Study:

  • Title: Epidemiology and control of SARS-CoV-2 epidemics in partially vaccinated populations: a modeling study applied to France.
  • Principal Investigators: Paolo Bosetti, Cécile Tran Kiem, Alessio Andronico, Vittoria Colizza, Yazdan Yazdanpanah, Arnaud Fontanet, Daniel Benamouzig and Simon Cauchemez.
  • Study Population: Individuals in metropolitan France.
  • Methods: An age-stratified deterministic compartmental model describing the spread of SARS-CoV-2 in metropolitan France was developed.

Objectives of the Study:

Principal Objective: To study and anticipate how partial vaccination of the French population should change the epidemiology of SARS-CoV-2 and to determine the implications for epidemic control.

More about this Study:

Scientific Context: The SARS-CoV-2 pandemic that began in December 2019 has caused more than 3.8 million deaths worldwide and brought health systems to the brink of collapse in many countries. Moreover, the drastic control measures that were implemented to limit its impact have had dramatic socio-economic consequences.

Vaccines have proven effective in reducing the severity of SARS-CoV-2 infection, the risk of infection and transmission. Their introduction offers a way out of this difficult period. However, given the high transmissibility and severity of SARS-CoV-2, very high vaccine coverage may be necessary to completely relax control measures. This goal may be difficult to achieve in countries, such as France, that are affected by vaccine hesitancy. In these places, SARS-CoV-2 may still be circulating in autumn 2021 and affect health systems. In this new era in which a substantial part of the population will be vaccinated, the epidemiology of SARS-CoV-2 should be different from before the distribution of the vaccines.
It is important to anticipate these changes to determine how control measures might evolve to ensure that they keep the epidemic under control while minimising costs to society.

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