I put in my previous message one of the most important reason, if not the most important, why it is difficult to have good data about the mask efficiency. Here it is again : Relatively low numbers of people followed the guidance about wearing masks or about hand hygiene, which may have affected the results of the studies. If you can not trust the people you use as data, you can not trust your results, and for something as trivial as wearing a mask, we have seen that people cannot be trusted... So, how can you produce proof that masks work ?

Yes surgical masks are effective. Not 100%, but they have a good efficiency to prevent people to spread the desease. They stop the biggest dropplets when you speak or cought, no debate. They also stop smaller particles because of the electrostatic effects and the diffusion effects. Also, the mask mesh doesn't look like a football net. It's more like a dense forest. Adding to that the fact than small particles don't move in straight lines ( brownian movement ), it makes the surgical masks have a non neglectible efficency.

The main reasons surgical masks are recommended above the others (n95/p2),are that other masks are more disturbing to wear and they cost more than surgical masks.