Vaccines are basically Gene Wilder and Cleavon Little in Blazing Saddles or the Three Amigos.
Q. How exactly do vaccines work if they don't prevent a virus from entering your body?
A. OK, so do you ever watch those cop dramas on TV? They do a bunch of research, figure out who the bad guy is, and then “put out a BOLO” to find the bad guy?
That’s kind of what a vaccine is.
It’s the Wanted poster that they give to the cops (which is your immune system) so that they know what the bad guy looks like, so that when they run into the bad guy, they recognize him and take him out. It’s also the specialist that comes in and trains the locals on how to deal with this particular bad guy.
A vaccine “trains” your own immune system to recognize the virus. Usually, the immune system can only learn what a virus “looks” like by actually coming in contact with a virus. But since they won’t know it’s a “bad guy” until it does “bad guy” stuff, that gives the virus time to run around doing damage before the immune system a) figures out that it’s the bad guy and b) calls in all the troops for the manhunt.
This is bad. This is reactive. This necessarily requires damage to the body first. And a lot of time, the damage can be too extensive to repair, or it can kill you before your immune system has the time to mount an effective response. Or worse, the damage is to the immune system itself, preventing any defense of any illness at all.
So a vaccine delivers something that *looks* like the virus but doesn’t do any damage. A mock-up, a model, a training dummy. That way, the immune system learns to recognize it first, and it rallies the troops immediately and has them on standby, ready to go, before the virus ever enters the system. So when the virus DOES finally enter (if it does), the SWAT team is right there, already geared up and trained on this guy’s specific tactics.
There may still be a firefight. The bad guy might still win. But it’s WAY WAY WAY less likely if all systems are on alert and geared up and waiting to ambush the virus, rather than allowing the virus the opportunity to sneak in and start sabotaging stuff without the immune system knowing about it.
Vaccines are the warning poster, the BOLO, the call to action, telling your own body that there is an imminent threat on the horizon, go to DEFCON 5, batten down the hatches, and get ready for war. Then your own body does what it can to prepare itself based on the information it’s given in the warning poster / vaccine.
With enough warning and the proper information, our bodies can usually mount an effective defense, but it’s still gonna be a fight and some people are immunocompromised (meaning that their body doesn’t have, like, a functional SWAT team, they have a dinky little rural sheriff’s office with 2 deputies and a couple of shotguns and that’s it). So it’s really important that all the surrounding towns (people) mount a good defense, that way the virus never even makes it into the county and the people with the little rural immune systems never have to take on the big fight that they can’t even hope to win. And if enough counties have enough towns on alert, we remove all the possible places that the bad guy can go to ground and hide, and if it can’t go anyway, it dies out.
Vaccines are the early warning system and training montage. Your body is still doing all the work. For most people, that’s very effective as long as the intel the body has about the virus is good. For some people, they require everyone else to keep the virus out of the population around them because they’re not equipped to mount their own defense. As long as we reach a minimum number of vaccinated people in the population (80% or more get the “warning system”), and we get the required “continuing education” training (i.e. booster shots) for those viruses that need it, our collective biology does a pretty good job of repelling the invaders ourselves.
https://www.quora.com/How-exactly-do-vaccines-work-if-they-dont-prevent-a-virus-from-entering-your-body/answer/Joreth-Innkeeper