My opinion is that what we really care about is the net effect of masking. Do more or less people become sick and die wearing or not wearing masks.
You are only looking at half the story.
In a pandemic, there are two main objectives we want to achieve: (1) to reduce pathogen transmission and the death or illness that it causes; (2) to try to allow people to live as normal a life as is possible, which is important to keep the economy going, as well as important for people's mental health.
If people feel more protected due to mask wearing, so that they then venture out of self-imposed lockdown towards more normal life, this riskier behaviour may negate the benefits of masks, and so prevent masks from achieving objective (1). Thus it is quite possible that you find mask wearing does not reduce pathogen transmission in a study, due to this change towards riskier behaviour.
But nevertheless masking will still have been a success, because it results in achieving objective (2): allowing people to live more normally, which is equally important.
This is why in real world masking studies, you cannot just look at whether objective (1) was achieved; you also have to look at whether objective (2) was achieved. Achieving either shows that masks are a success.
And exactly the same is true for real world studies on the efficacy of COVID vaccines (at least for vaccine studies which do not have a double-blind placebo controled group).
As we know, once you are vaccinated, you feel more protected from the ill effects of COVID such as death. Therefore you are happier to leave any self-imposed lockdown, and return to a more normal life. That behavioural change towards living a more normal life again results in higher risk of exposure to COVID, and thus a higher risk of death. So that may partially negate vaccination achieving objective (1). But nevertheless, the vaccine allows you to achieve the equally important objective (2).
So with vaccination, just like with masks, success is measured either by achieving objective (1), or achieving objective (2), or a bit of both.
Edited by Hip, 11 December 2023 - 08:54 PM.