The CDC now says
studies showed effectiveness against COVID emergency-department and urgent-care incidents was “87% and 91%, respectively, during the two months after a third dose” of the [mRNA vaccine] booster,” but that it decreased to 66% and 78% by the fourth month after a third dose.
That’s for both the Delta and Omicron variants of the Wuhan Virus.
Leave aside, for the moment, the lack of credibility of anything coming from the Biden-Harris’ CDC; instead, accept, arguendo the narrow claims of the CDC paper Just the News cites.
Unmentioned in the CDC’s paper is the extremely low baseline rate of “emergency-department and urgent-care incidents.” The seemingly sharp reduction via the boosters is real in a purely narrow, statistical sense, but starting out so close to zero, it remains an open question of whether the booster really provides much value—even were its effects to last much longer.