Where on earth do you get the notion that no vaccine lasts longer than 7 years?
Also, how does one get the power to down vote.
Also, how does one get the power to down vote.
just vote everyone else up. same effect.
The existence of booster shots certainly doesn't prove that no vaccine lasts more than seven years. At best it proves that those specific vaccines don't last forever. There are plenty of vaccines where you don't get booster shots though.