Do you see how they are referring to deaths after vaccination as "breakthrough covid deaths"?
You're misquoting. This is the original:
The result is the rare breakthrough case consists of mild to moderate Covid disease after exposure to the virus.
"Breakthrough covid cases" are cases in which the patient contracts COVID, usually mild, after having been vaccinated. Sometimes after one shot; more unusually, after two. From what I've read, none has resulted in death or even hospitalization.