An interesting question is: what is the Herd Immunity rate? As hopes that the infection rate is close to the herd immunity rate as more antibody tests have come in, optimists have shifted toward hoping that the herd immunity rate is actually much lower under Let ‘Er Rip conditions than the common ~60% estimate.
We don’t know, but one useful way of checking is to see how high the Ever Infected Rate has gotten in the hardest hit areas. From the Bergamo Chronicle, via Google Translate
Bergamo serological tests, the results of Nembro and Alzano arrive: 61% positive
Serological tests on 750 citizens of Nembro and Alzano. In the meantime, a machine with 2,000 tampons a day is expected
Google Translate is pretty amazing, but I don’t think it’s fully optimized for Italian, judging by that second sentence.
by Armando Di Landro, April 30, 2020
The Lombardy Region continues to impose utmost silence on the ATS on the results of the serological tests, on the one hand because the final result will not be indifferent and will understand how many Bergamoers actually contracted Covid-19, then developing antibodies, starting from citizens for which there had been no official diagnosis using the swab;
Somebody should run a Google Translate on the 1923 hit song “Yes, We Have No Bananas.”
on the other hand, however, because the initial numbers could impress: the tests started with Alzano and Nembro, the countries most affected in the phase of absolute emergency, calling moreover to make the withdrawal the citizens who had been placed in quarantine for contacts with the infected, or remained at home sick due to suspicious symptoms. And so it is, the high percentages long awaited by Palazzo Lombardia, are there and filter anyway: out of 750 blood samples taken to citizens of Nembro and Alzano between Thursday and Tuesday (there were 1,500 in all but about half were sent to Seriate) and analyzed at the Papa Giovanni hospital, in 61% of cases the serological test gave “positive” results, which means feedback on the development of neutralizing antibodies and therefore on having already encountered the disease. A slightly lower percentage, between 58 and 59%, would emerge from the analysis at Bolognini di Seriate.
Okay, I think that means that in 3 northern Italian towns with huge death rates, about 60% had antibodies for infection by the novel coronavirus in April.
That 60% figure is in line with the most common estimates of Herd Immunity.
One possibility is these 60% figures are due to Herd Immunity Overshoot, in which a roaring pandemic such as in northern Italy recently, can shoot past the minimal needed levels. But if brilliant public health experts could ease the infection rate just up to the minimum, perhaps this could be lower.
On the other hand, we have no proof that these 60% figures in these 3 towns are due to herd immunity. They could be more due to the ferocious lockdowns imposed upon these towns last winter.