News > Covid booster efficacy wanes significantly by fourth month: US study

Covid booster efficacy wanes significantly by fourth month: US study

The efficacy of third doses of the Pfizer and Moderna mRNA vaccines wanes substantially by the fourth month after administration, a new study by the US Centers of Disease Control and Prevention (CDC) said Friday. 

Though it's now well documented that vaccine efficacy goes down after two doses, relatively little has been published on the duration of protection after a booster.