I’ve read some potions show they have been reinfected with Corona19 If that’s the case, how does a vaccine work?
People work all the time trying to come up with a “universal vaccine” for a group of bugs. Flu, the common cold, HIV*, etc. all evolve enough that the standard vaccines don’t work on all of them. Similar to how the body can’t stop all of them.
But a virus has multiple sites on it’s coating that might be used to trigger an immune response. Some of these vary a lot, and hence the issue. But some areas don’t. For various reasons the body’s immune response goes after the more mutable areas first.
But if a suitable immune response can be invoked via vaccination on one of the more stable areas, then you could have a vaccine for the entire group of viruses.
So you incubate a bunch of batches of viruses in a family. Chop things up. Separate out various fractions. Look for bits that are common to different batches. Start injecting those bits into animals and see if there’s a decent immune response. (Or you use a computer and some sequencing software.)
- HIV mutates within a person, staying ahead of the person’s immune system until the person … no longer has an immune system.
… And so, in use, some vaccines consist of live virus, very similar to the dangerous virus, but fairly harmless in them selves, and you get infected, and thus get immunity to the dangerous virus.
And some vaccines consist of “dead” virus, which has been heated or chemically treated until it degrades enough to not be infective, but is still recognisably the dangerous virus.
And some vaccines consist of “chopped up virus fragments”, which don’t reproduce, in the same way you wouldn’t be fertile if you were chopped up in to pieces.
And all of these methods sometimes go slightly wrong, and you get a live virus that, in spite of best efforts, turns out dangerous to a small number of people, or an inactivated virus that really is too degraded to work properly for a small number of people, or a chopped up virus that triggers a dangerous immune response in a small number of people, or more generally, a vaccine that just doesn’t work very well.
Mostly these effect a small number of people, much smaller than the protective effect on a large number of people, and trigger a search for a better vaccine. Sometimes they affect a larger number of people, and trigger discussion about the validity of using that vaccine. Always they are part of the discussion about if the number of cases of the disease is large enough that a vaccination program should be started or continued.
On top of all this… people don’t live forever. You just loose immunity to things over the years, which is one reason why in some cases it’s worthwhile to have a “booster” vaccination later on.
Melbourne, I get all that. My point is - aiui vaccines work by triggering your immune system using a non-virus particle similar to the virus (and yes there a varying ways). The idea being that when you get infected, the immune system is rearin’ ta go, doesn’t let it spread. But if you can get the virus, and survive it, presumably you have an immune system ready to go for that virus. So whence re-infections? Or, or specifically, if the immune system doesn’t respond to a virus it just beat for realz, why would it beat it after exposure to something merely similar?
To expand on this:
The areas that the body’s immune response goes after become more mutable, due to evolutionary pressure. There’s little selective pressure to change areas the immune system doesn’t see, and a great deal to change areas that do trigger an immune response.
- You don’t always get a good persistent immune response that lasts forever.
- And anyway, the next time, the virus might be subtly different.