@ZoeMcLaren Thanks for tweeting about this article. I'm going to leave the matching issue for another day, but I want to add a note of caution as one of the authors. We did not claim, and the data do not directly address, the reduction in total infections.
@ZoeMcLaren We used the word "documented infection" to highlight the fact that many infections may have gone undocumented, especially those not symptomatic. The documented infections is a mixture of symptomatic (probably most of them) and asymptomatic (probably a smaller fraction)
@ZoeMcLaren As a consequence, it is mathematically possible to have a big effect on documented infections but a smaller effect on total infections. As an extreme case (likely more extreme than the truth) suppose that symptomatic infections are detected with probability 90% and
@ZoeMcLaren asymptomatic with probability 5%. Then a vaccine which converted all symptomatic infections to asymptomatic (rather than preventing them) could look up to 85% effective against documented infections. It is actually an important problem to work out the algebra of
@ZoeMcLaren what you'd have to assume for these results to be consistent with 0, 10, 20, etc percent reduction in total infections. We haven't done that, and should. But all we showed in the paper is the reduction in symptomatic infections (similar to the RCT) and in
@ZoeMcLaren documented infections. To be clear, this is absence of evidence (at least until further analysis). My personal bet is that mRNA vaccines will reduce transmission 80-90%, but I don't think there is evidence for that yet. Suggestive (esp the Moderna second-dose swabs) but not hard
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