Vaccines work by stimulating the immune system to respond to a specific thing. Most of the vaccines we use are designed to prime the immune system so that it's ready to fight off some kind of disease, like whooping cough, polio, or influenza. Some vaccines can have more specialized functions, like stimulating the body to attack cancer cells, kill rogue autoimmune cells, or prevent pregnancy. We'll look at what they do in later posts, for now, let's look at the kinds of things that can be used as vaccines.
It's an amazing assortment. Even more amazing is that these items don't all work in the same way. Some stimulate the immune system through one pathway, some work through another. Some work better when they're ingested orally, some need to be injected into muscle. Some require an extra substance called an "adjuvant," others work without adjuvants.
One thing that all of these substances have in common is that they, or the substances they encode (in the case of DNA), will trigger the growth of specific immune cells, and those immune cells will be ready to attack when a similar substance appears again.
One other thing they have in common is that none of these are drawn to scale.
We'll fill in more details later.