Spain’s second wave of Covid-19

Did this happen? Were Spain’s hardest hit provinces in the spring spared in the second wave?

To get a quick sense of the answers to those questions I plotted the cumulative number of cases per 100,000 population in the Spanish provinces since June 15 against the proportion of the population in the provinces that tested positive for antibodies after the first wave. If herd immunity were playing a large role in suppressing cases in the second wave, we would expect to see a negative relationship between provinces with high levels of antibodies in the population at the end of May and total case counts since that time…

Instead of a negative correlation, there is a positive, although weak, correlation between having higher prevalence of antibodies in the population and having a higher case rate in the second wave.

…Take Madrid for example, if roughly 13% of the population had antibodies after the first wave, at least one of the low-HIT models estimates the Rₑ would be approximately 60% lower than than the unmitigated reproductive rate (R₀). If population immunity were reducing transmission in the Madrid area by 60% below unmitigated levels, it seems unlikely Madrid would again have one of the highest rates of infection in the second wave [yet it does].

…Ultimately, the strongest conclusion that can be drawn from this look at infection rates is that there is not clear evidence herd immunity is playing a significant role, yet.

Also take a look at a deeper dive looking for herd immunity in Sweden (spoiler alert: no signs of it yet).

It is fine to call this inconclusive, but still the pattern predicted by standard herd immunity claims is not yet showing up.  Here is the whole piece from Kbenes, very useful.

And elsewhere, this was not supposed to happen, as New York Orthodox Jews also have been cited as a “herd immunity” community:

Officials this week released statistics showing that the positivity rate in some Orthodox Jewish neighborhoods [in NYC] had grown to anywhere from 3 percent to 6 percent, significantly more than the city’s overall rate of between 1 percent and 2 percent. Officials are especially worried about the positivity rates in the Brooklyn neighborhoods of Borough Park, Midwood and Gravesend, which they have referred to as the “Ocean Parkway Cluster.”

Here is that full story (NYT).


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