Martin Kulldorff

Point 2: household studies of transmission in kids are biased. Because if you detect your index cases by looking for symptoms, you’re not going to catch the kids who are less likely to have symptoms as index cases. Duh. Did I mention non-symptomatic transmission is a thing? 3/n

Point 3: schools are hard to study because we closed them quick, and at a point when we didn’t really have good testing. So what did happen is hard enough. What *would* have happened is even harder 4/n

(btw pls note that statements that “there was an introduction to the school without transmission!” are not so helpful. The overdispersion means we expect that a lot of people won’t transmit. We need better population data not anecdotes) 5/n

So this is what I think. Consistent data from household studies suggest that younger kids are less likely to get infected, and that if they do they are less likely to transmit. But that’s not enough… the contacts kids make in schools are different 6/n

This is where this study comes in – it is mostly a comparison of Finland and Sweden. Two countries with very different approaches to the pandemic. Both shut down High Schools and colleges. But Sweden kept schools for younger kids open. https://www.folkhalsomyndigheten.se/contentassets/c1b78bffbfde4a7899eb0d8ffdb57b09/covid-19-school-aged-children.pdf … 7/n

I’m not so interested in the data about the younger kids in this; as the report says they are probably massively underestimating infection in children given the fact that testing was diverted to severe cases elsewhere in older cohorts. As like - everywhere? So ignore that 8/n

However that can’t explain the fact that people working with those younger kids were no more likely to be infected than people in the general community. I should point out that for Sweden, this has been a pretty high risk in the community - the per capita mortality is high 9/n