Of course we do. There have been multiple serology studies, multiple whole-town tests in different states and different countries, and let's not forget cruise ships. We have data from all over the place to establish that about 40% of COVID-19 cases are asymptomatic, another 40% show mild symptoms which don't require medical attention, about 5% of cases result in hospitalization, 3% in the ICU, and 0.65% die. We knew that back in May 2020. Everything since that time has been consistent with that, though we've seen some variation as monoclonal antibody therapy became more available and as variants like the UK variant started pushing back with higher severity. But overall, it's consistent.
"I've had people insist to me that even having a case of the original virus did not make you immune. They've finally stopped doing that."
There were no changes to the S-protein between the original Wuhan SARS-CoV-2 and the April 2020 variant. Anyone infected with either of those has only about a 1 in 10,000 (0.01%) chance of becoming reinfected with either of those variants. That changes significantly when you introduce the Brazil and South Africa variants, which do have structural changes to the S-protein resulting in diminished function for antibodies produced against the April 2020 variant. Again, this has all be readily observed and studied. This is actually happening in the wild today.
"If what you say is true then there will have to be a China vaccination, a Brazilian vaccination, and a South African vaccination. And then vaccinations without end. Who's next? A Luxembourg vaccination?"
A booster is only necessary when the original becomes ineffective. Testing for Pfizer, Moderna, and J&J (all the vaccines available in the US today) demonstrates they remain effective against all known variants. However, because of the reduction in effectiveness for the existing antibodies, Moderna has produced and is testing a booster specifically for the South Africa variant. I doubt it'll be necessary, but it might be useful for those who don't have a strong immune system to get something more specific to that particular variant.
"In numbers so small as to be insignificant to the country as a whole and so therefore irrelevant. Which also means that we have very limited data on the long term effect of the so-called vaccine. Widespread vaccinations only started in more-or-less 2021 and by your own admission have only reached 16% which is not so widespread at all."
We definitely have limited data at this point, but that's always the case for any new medicine. And that's something each individual needs to weigh in their own personal risk:benefit analysis. I absolutely encourage everyone to make their own informed decision. For me, I looked at all the data available and made the decision that it makes sense for me. Maybe you look at all the data and say you'd rather wait or that you don't think you want to get any of the vaccines for COVID-19 ever. That's certainly fine. As long as we're honest about the risks and the benefits are, each person can make that decision.
What we do know so far is that the vaccines available in the United States are safe and effective. Moderna and Pfizer are ~95% effective. Based on data from Israel, Pfizer is 94% effective at preventing asymptomatic infection and 97% effective at preventing symptomatic infection. Moderna and Pfizer both carry a small risk of serious allergic reaction. That risk is about 1 in 90,000 people for Pfizer and about 1 in 400,000 for Moderna. Most of those who've had a reaction to either are people with a medical history of severe allergies (the people who have to carry an EpiPen with them everywhere they go). Those reactions are quickly reversed, typically with a shot of epinephrine. If you have an EpiPen with you at all times, you probably shouldn't risk those two. But the J&J shot should be fine. If you're ardently pro-life (as I am), the J&J shot probably isn't for you as they used fetal stem cells in the R&D process. Moderna and Pfizer did not. Novavax also did not, their product looks great in testing, and they should be approved within the next month.
Still waiting for some evidence of your expertise supporting what you say or at least links to someone with expertise. Until then pffffft to you.