Second paragraph, booster shots. Also, that CDC link is not based on science. More a combination of marketing and the effects of hygiene and nutrition. Same for the immune.org link.
just vote everyone else up. same effect.
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.