We keep hearing about how we will know more once we get the first serology data to find out just how many people have been exposed, infected and thus (presumably but not certainly) immune to further COVID19 infection. We now have a preprint just released of a study from Santa Clara, California of over 3,300 people. The news is not great, though there are certainly many different ways of defining ‘good’ or ‘bad’ news in this case. The study found that 1.5% of people in the study were seropositive; adjusted for demographic weighting the number was 2.81%.
Looking to the future it would be great to learn that the contagion was far more prevalent in the population than we thought. That would mean that the lethality of disease was relatively lower. Much more importantly it would place us much closer to achieving significant population wide exposure (and likely immunity) which would at least slow if not stop the spread of the disease in future outbreaks.
This is an early, pre-peer review version of the study. The tests are new. But if this number is close to accurate it suggests that even in a relative hotspot the population is all but untouched by the disease and thus remains almost entirely vulnerable.