It’s not that I “don’t believe in Evidence-Based Medicine”, it’s that you didn’t mention in your first comment that your were talking about a different study, so I really didn’t know what you were talking about. Thanks for giving the link.
The Marine study doesn’t address the effects of masks. Both the participants and nonparticipants wore masks. The actual difference between those groups was that the participants were asked about symptoms, tested, and isolated if positive at day 0, 7, and 14, versus only on day 14 for nonparticipants. It gives us some (unsurprising) evidence that surveillance testing and isolation helps: on day 14, at least 11/1760 (0.6%) and possibly as many as 22/1847 (1.2%) participants were positive, compared to 26/1554 (1.7%) nonparticipants. Unfortunately the reporting is not great, so we don’t know exactly how many participants were positive on day 14. And this is pretty weak evidence: we don’t know how many of the nonparticipants would have tested positive at day 0, so it’s hard to say how much of the day-14 difference was due to weeding out infected participants versus the participants possibly starting with a lower infection rate.
It’s not that I “don’t believe in Evidence-Based Medicine”, it’s that you didn’t mention in your first comment that your were talking about a different study, so I really didn’t know what you were talking about. Thanks for giving the link.
The Marine study doesn’t address the effects of masks. Both the participants and nonparticipants wore masks. The actual difference between those groups was that the participants were asked about symptoms, tested, and isolated if positive at day 0, 7, and 14, versus only on day 14 for nonparticipants. It gives us some (unsurprising) evidence that surveillance testing and isolation helps: on day 14, at least 11/1760 (0.6%) and possibly as many as 22/1847 (1.2%) participants were positive, compared to 26/1554 (1.7%) nonparticipants. Unfortunately the reporting is not great, so we don’t know exactly how many participants were positive on day 14. And this is pretty weak evidence: we don’t know how many of the nonparticipants would have tested positive at day 0, so it’s hard to say how much of the day-14 difference was due to weeding out infected participants versus the participants possibly starting with a lower infection rate.
Correction: for participants on day 14, it was somewhere between 11 and 33 out of 1847 (0.6%-1.8%). Not that it makes much of a difference.