It is estimated that between the start of the pandemic and March 2021, around 20% of French people were infected with the SARS-CoV-2 virus , which is far below collective (herd) immunity. In this context, a large-scale vaccination campaign is necessary to relax the control measures and resume a normal life.
If the vaccination campaign concerns only the adult population, for R0 = 4.0, it would be necessary that more than 90% of adults be vaccinated for a complete relaxation of the control measures to be considered. These high levels are explained by the fact that if only adults are vaccinated, a large epidemic is still expected in children, contributing to the infection of unprotected parents and grandparents. If vaccines are shown to be safe in children and to effectively reduce susceptibility in this population, immunization of 60-69% of 0-64 year olds and 90% of over 65s may allow release complete control measures.