One issue is that the study design and probably analysis is very similar to the Santa Clara study (they are using the same test kits and have shared coauthors on both studies). It's not really independent replication when both are potentially using flawed kits and analysis.

That's because the methods and authors have major overlap. The USC study reported here is a collaboration with the same group at Stanford:

https://news.usc.edu/168810/usc-covid-19-antibody-researcher...

The participant selection here was done differently, but the same problems arise with the false positive rate of the tests.

I'm not sure if we can consider this independent support: both studies use the same antibody test. Any problems with the test itself (or our understanding of problems with the tests) will be present in both studies.

also in line with the dutch results a week ago (https://www.nytimes.com/reuters/2020/04/16/world/europe/16re...)

Well, a lot of the same people are involved in both..

Looking forward to what the science heads on my twitter feed say about it. They were positively withering in their criticism regarding the Santa Clara study.

How do you explain the low number of hospitalizations and deaths in LA vs NYC? If these numbers hold then you’d expect NYC to be close to herd immunity given the difference in fatalities.