Do you get tetanus boosters? MMR? All bugs are different, some the antibodies will last a lifetime. Some they won’t.
That is not how this was sold.
It was sold initially as “You won’t get sick”
Then it morphed to “You won’t get as sick”
Then to “You can still get infected, pass it on and mitigate the symptoms but, you won’t die”
and now “You need a booster” and maybe more...