that's probably just because vaccinated people think they're safe when they're not so they're not as careful as the control groupDoes negative effectiveness mean that actually you are more likely to catch COVID if you had a Moderna shot than without it? I wonder whether the issue is with Moderna or mRNA vaccines in general - they failed hard in previous non-COVID outbreaks, maybe the same is happenning now?
Anyway, China has Walvax which seems to be similarly effective as Moderna