Lets put it this way
there is a 50-75% with antibodies in BP.
No new infections (even though BP is fully reopened)
Not 50-75% of people with antibodies, 50-75% of people
tested with antibodies. Surely you realize those who think they’ve had it are far more likely to submit to a blood test to confirm than those who don’t? 50-75% is a really big range anyway. That could mean we’ve prevented a full half of deaths, at least.
So maybe at the point, we went into lockdown we should have only locked the vulnerable?
Why isn't the 30% without antibodies getting infected now? We have lots of ppl still testing positive?
To your first point, it has merit but if everyone infected would be running around as usual the odds of those “locked up” getting it would rise dramatically as well, because the virus would be (was?) circulating at immense levels. See Sweden, Ireland, and the U.K. as well as use common sense.
To your second, it seems that testing positive later into your infection doesn’t indicate contagion, at least that’s something doctors are assuming (hoping). See the article linked to by Rabbi Dr. Glatt for more on that. The vulnerable people without antibodies are presumably mostly still locked up, and the level of people walking around with antibodies is presumably very high relative to the amount of people walking around with infectious virus.