Do we know how many “cases” there have been over the past 12 months? Because those people should also be immune.
This whole thing is such a sham.
Around 81 - 83 million in the US.
"Because those people should also be immune."
Presumably so, though there's some data that the South African variant shows some resistance to the neutralizing antibodies from the April 2020 variant. If that proves to be the case, there may be some who had mild or asymptomatic cases with the April variant who are susceptible to the South African variant. However, there's no hard data on this yet. For now, I would assume that the vast, vast majority of those who've had it once are pretty well immune to new infections. The documented exceptions to that have been exceedingly rare.
"This whole thing is such a sham."
The response from state and local governments certain has been. From lockdowns that are far more effective at driving small businesses out of business and family into poverty than they are at slowing COVID-19 transmission to governors like Newsom and Cuomo who forced nursing homes to accept known-infected COVID-19 patients, it's been one calamity after another.
The virus is very real. The response from state and local governments has been a nightmare. A textbook example of ineffective leadership. If it weren't for President Trump, we wouldn't even have these vaccines.
“Do we know how many “cases” there have been over the past 12 months?”
Estimates vary, but most everyone agrees that there have been more infections, than there have been cases confirmed by testing (now about 28.5 million in the USA). I believe that the actual number of Americans who have already been exposed, is over 100 million. CDC estimates 83 million, from Feb 2020 through Dec 2020. Other estimates have varied from 1/4 of the population, to as high as 2/3rds.
A lot of infected people had little to no symptoms, or had symptomatic cases before testing was readily available. The antibody blood test, to see if someone was previously infected, only works for a month or two after the infection clears - so authorities are forced to estimate from secondary measures.
They have had a survey program (Seroprevalence survey) with laboratory testing companies to scan random blood lab test samples for COVID antibodies. They even have a wastewater (sewage) sampling program, to estimate population-wide disease burden.