Anecdotally, I know someone who has been infected twice. Refuses to get vaccinated now because "why bother? I have great immunity now." With no sense of irony, given that he's already been infected twice...
How is that different from a vaccine?
In reality it seems that the immune system does tend to end up targeting the same protein that's in the vaccine, but may be targeting different portions of it (https://pubmed.ncbi.nlm.nih.gov/34103407/ talks about this). My understanding is that current data suggests the naturally acquired immunity is about as robust as the vaccine acquired one, but this wasn't a given.
How does he know he was infected twice?
Saying that a PCR test returned positive values two times isn't a great answer - since by its nature PCR is only counting the existence (above the programmed threshold post amplification).
Serology is the only way to know for certain you were/are infected.
This highlights one of the bigger issues we have: PCR test are a very cheap and a useful way for getting estimates but their failure rate is high enough to make it pretty poor basis for doing large scale data analysis.
Long haul COVID doesn’t spring back to life and give you a fever for 12 days straight. I had essentially the same symptoms both times: fever, extreme fatigue, a dry cough, complete loss of taste of most things, etc.
Long story short, even if you didn’t get tested one of the two times (I tested positive both times) it’s pretty freaking obvious what you have as long as you don’t have a mild case. My wife got it this time around, and we got her an infusion of monoclonal antibodies early as she’s pregnant. She only had a fever one night, and in trying to explain how she felt I asked her “it feels like you just want to stop existing, right?” She agreed. Before that night it just seemed like a cold for her.
edit: surprising downvotes so I probably didn't communicate my point well.
I can't imagine a reason why natural immunity would be harder to quantify than vaccine induced immunity. It would seem to me the methodology to quantify both would be very similar.
but this is a good point I hadn't considered, thanks
With an infection, you have no control over the degree of exposure, so on top of the variability of the response comes the variability of the exposure.
Additionally, in case of exposure of the full pathogen, there is some variability to what part of the pathogen the immune system will respond. That part can actually be a good thing in total.
Pardon my ignorance, but does this mean by contrast that vaccines are designed to induce a uniform response across immune systems?
EDIT: A reply (deleted before I could respond) mentioned that immune systems will combat the infection by some "pattern" of it's own design, but a vaccine will encourage the immune system to respond in a predetermined way, (increasing likelihood of uniformity, answering my question).
Is this accurate?
Also not an expert and curious, would that not be a (the?) design goal of any vaccine?
A more uniform response than the pathogen itself? Yes. But I think the actual goal of modern vaccination is not a uniform response, but a directed response. Don't waste your time looking at these parts of the virus, spend it on this (important) part.