> Sometimes our immune systems don’t work though. In that case we need vaccines. Sorry, but that sounds a bit confused. Vaccines bring information to the immu

> Sometimes our immune systems don’t work though. In that case we need vaccines. Sorry, but that sounds a bit confused. Vaccines bring information to the immune system to train it to recognise something as a threat faster than it would otherwise. Think of it as a "wanted dead or alive" poster. The poster doesn't go out and kill the baddies on its own. The poster is distributed to the sheriffs of the towns, so if the baddie shows up they recognise it for what it is before the baddie robs the bank. In this parallel the baddies are the infectious material (virus, or bacteria), the sherrifs are the immune system, and the poster is the vaccine. If your immune system don't work, first of all that is very bad, second you don't need a vaccine. Because it won't help you! Same as sending wanted posters to a town with nobody who could act on them wouldn't make the town more secure.