Maybe, maybe not. It boggles my mind that there isn’t much data on antibody levels of reinfected patients at time of infection. The cynics will say that such research is being suppressed for political reasons, I just think it’s hard data to isolate (recovered people who tested for antibodies recently before reinfection)
Do the math.
August 2020 we were discussing reports of about 20 documented reinfections world-wide. At that time, about 26 million covid cases had been reported, so let's say the chance of reinfection was 1 in a million.
August 2021 we discussed the article from Israel which looked at reinfections among members of the Maccabi kupat cholim. It has not been published in peer-reviewed form, but it's all we've got to go on. It was confusing, and I hope I got the numbers here right.
https://forums.dansdeals.com/index.php?topic=123776.msg2491027#msg2491027They looked at people who'd had COVID in Jan-Feb 2021, and had a second COVID infection by the end of June, that is, about 5 months later. Out of 16,000 cases, there were 19 reinfections, so about 1 out of 1000.
When they included people who'd had COVID earlier, from Feb 2020-Feb 2021, and had a second COVID infection by the end of June, that is, 5-17 months later, they found a higher reinfection rate. Out of 46,000 cases, there were 108 reinfections, or about 1 out of 500.
I've rounded off numbers here, and not sure I got this right, but I think the order of magnitude is right. That is, among people who've recovered from COVID, something like 1/500 to 1/1000 were getting a second case of COVID by the end of June.
This was before the delta peak, so let's take the higher number, and assume 1 out of every 500 COVID recoverees will be infected a second time with COVID this month. Once they're reinfected, they'll naturally increase production of antibodies, so if we want to know their level of antibodies BEFORE that infection, we would need to measure antibodies of 500 recoverees in order to find ONE person who is reinfected. But to draw reliable conclusions, we would need to find more than one. If we want to reach a sample size of 20 reinfections, we would have to examine 20x500, or about 10,000 recoverees, in order to find those 20 who will be reinfected.
For each of those 10,000, we'd need to measure there antibodies frequently - perhaps once or twice a week - so as to catch their antibody levels before the infection. As Euclid mentioned, it's not easy to get 10,000 people to agree to give frequent blood samples for something like this.
Instead of studying 10,000 people for one month, we could study 1000 people for ten months, but of course, that's longer than we want to wait for an answer.
The point is that it TAKES TIME to get an answer to the question of whether a particular antibody level can be used to determine a person's immunity to covid. Some recent studies show a different chemical in the blood of recoverees that seemed to correlate with immunity, so that's another direction the research is taking.