La première étude a porté sur les hospitalisations et les visites aux urgences et aux centres de soins d’urgence dans 10 États, d’août à ce mois-ci.

It found vaccine effectiveness was best after three doses of the Pfizer or Moderna vaccines in preventing COVID-19-associated emergency department and urgent care visits.

Protection dropped from 94 percent during the Delta wave to 82 percent during the Omicron vague.

Protection from just two doses was lower, especially if six months had passed since the second dose.

Officials have stressed the goal of preventing not just infection but severe disease.

The second study focused on COVID-19 case and death rates in 25 states from the beginning of April through the end of December.

People who were boosted had the highest protection against coronavirus infection, both during the time Delta was dominant and also when Omicron was taking over.

Ces deux articles ont été publiés en ligne par les Centers for Disease Control and Prevention.