Vaccine-induced and naturally-acquired protection against Omicron and Delta symptomatic infection and severe COVID-19 outcomes, France, December 2021 to January 2022

We assessed the protection conferred by naturally-acquired, vaccine-induced and hybrid immunity during the concomitant Omicron and Delta epidemic waves in France on symptomatic infection and severe COVID-19. The greatest levels of protection against both variants were provided by hybrid immunity. Protection against Omicron symptomatic infections was systematically lower and waned at higher speed than against Delta in those vaccinated. In contrast, there were little differences in variant-specific protection against severe inpatient outcomes in symptomatic individuals.

Automated summary

Hybrid immunity provided the greatest protection against both Omicron and Delta variants. The protection against symptomatic Omicron infections was consistently lower and declined at a faster rate in vaccinated individuals. However, there were little differences in variant-specific protection against severe inpatient outcomes in symptomatic individuals.