The Danish paper on negative effectiveness can be because Denmark required proof of vaccination to attend large events. If some of those events were superspreader events you would see an apparent negative effectiveness.
Same sort of result out of Canada, which also required vaccination for large events:
So the idea is the boosted/double-vaxxed risk-compensate with their behavior to an extent that they’re at more risk than, perhaps, a more isolated unvaccinated person?
The Danish paper on negative effectiveness can be because Denmark required proof of vaccination to attend large events. If some of those events were superspreader events you would see an apparent negative effectiveness.
Same sort of result out of Canada, which also required vaccination for large events:
https://www.medrxiv.org/content/10.1101/2021.12.30.21268565v1