In another Vikings thread, Mark Anderson asked:
...does the vaccine wear out in time(thus the push for boosters)?
Vaccines don't wear out. They provoke an immune response and go away rapidly. Some aspects of the immune response persist (B-cells, various types of T-cells) and some may wane over time (antibodies).
For example, the COVID mRNA vaccines are gone in 72 hours. Your body rips apart mRNA quickly. (Because all vaccines are eliminated rapidly, any adverse effects have shown up within 6 weeks.)
The antibodies decrease over time — this is true for any disease: otherwise your blood would be clogged with antibodies.
The B-cells that generate antibodies often persist. They can ramp up antibody protection quickly if you are re-exposed, but the Delta variant reproduces to rapidly you can get an upper respiratory tract infection while they generate enough antibodies that (usually) prevent an infection elsewhere (lungs, etc.). For the original SARS, they persist for at least 17 years.
The various T-cells may also maintain the ability to fight the disease. They appear to persist in this case as well; but the length of time isn't known yet.
For some slower diseases, the B-cells react fast enough to stop any infection (Delta is extremely fast). For Tetanus, the immune response wanes over time, and you need a booster every 10 years or so. For others, the immune response persists adequately for the rest of your life.
For boosters, they definitely jack up the antibody levels. So in a COVID-19 outbreak, maybe everyone would benefit from boosters to wake up the immune system and prevent infections. It's too early to know whether that booster increases the B-cell/T-cell response long term. As an aside, if the vaccines weren't developed in response to a pandemic, the dosage schedule might have been, say, 3 shots spaced 6 months apart. But then we'd still be waiting for the trials to finish, and obviously researchers choose a dosage schedule to get results quickly.
I give myself very good advice, but I very seldom follow it. --- Alice