I definitely found an epidemiologist on Twitter giving out about that study. The Science study used a convenience sample, which makes me believe that it's a very biased estimate of sero-prevalance.
Yeah, there are possible issues with the way the Science paper collected their sample, as well. The authors of the Lancet editorial allude to this in the next sentence:
"furthermore, comparisons of blood donors with census data showed no major difference in a range of demographic variables, and the mandatory exclusion of donors with symptoms of COVID-19 is expected to underestimate the true population exposure to the virus."
Here, the Lancet writers are trying to argue that the sample wasn't that biased, and therefore the Science paper was right, and therefore the current infections are due to "variants".
It's a very weird and convoluted argument. Comparison to demographic variables is irrelevant, and the second sentence doesn't address the actual concern with the Science paper (i.e. testing in Brazil was rare at the time of the study, so people with Covid sought out the study). Regardless, I think it's a red herring. It doesn't matter if the sample was biased or not -- you can look at the data as collected, and see that the upward adjustments were so aggressive that the conclusion of the Science paper is likely to be wrong.
