Effectiveness vs some viruses is not the same as effectiveness vs all viruses. Covid has been found to transmit with larger particles than the flu for instance. And, those studies were testing receiving particles by the wearer, not spreading them.
But those two points have repeatedly been discussed in this very thread over and over again for nearly 2 years now but you guys willfully pretend you never heard any such thing and just keep repeating the same refuted point about those old studies about non-covid and about the wearers risk of receiving the virus rather than spreading it.
Almost like you're being intentionally dishonest at this point.
My understanding was that, like influenza, covid was known to spread via "droplets" (i.e., aerosol particles that plate out rapidly due to gravitational settling). It was spread via "aerosols" (i.e., aerosol particles that plate out slowly due to gravitational settling) that was new. Moreover, according to the WHO, "COVID-19 and influenza and covid spread in similar ways.":
"COVID-19 and influenza spread in similar ways. Both COVID-19 and influenza are spread by droplets and aerosols when an infected person coughs, sneezes, speaks, sings or breathes. The droplets and aerosols can land in the eyes, nose or mouth of people who are nearby -- typically within 1 metre of the infected person, but sometimes even further away. People can also get infected with both COVID-19 and influenza by touching contaminated surfaces, then touching their eyes, nose or mouth without cleaning their hands."
https://www.who.int/emergencies/diseases/novel-coronavirus-2019/question-and-answers-hub/q-a-detail/coronavirus-disease-covid-19-similarities-and-differences-with-influenza
The assumption at the start of the pandemic was that covid-19 was primarily spread via large droplets. That's what led to the mask mandates, cleaning of common surfaces, hand washing, and so on. But it was always nonsense, and a minority of scientists and physicians were pointing that out from the start.
There was abundant evidence indicating that that primary mechanism for the spread of covid-19 wasn't large particles. One of the earliest examples, out of China before the disease was widely known to have spread elsewhere, was a person who was infected by a person who was sitting 40 feet in front of them, in a bus. This was well documented with surveillance cameras and widespread testing -- they never interacted or got any closer to each other, and there were no other possible sources of infection. There were also the studies, very early on, that showed that the virus could be detected, hours and days later, in the air in ventilation systems. Or, as superspreader events started being documented, the realization that almost none were happening outdoors, and when they did happen outdoors the number of people who were infected was a tiny fraction of comparable indoor events. None of these made sense with large droplets, which precipitate out of the air in just a few seconds, and shouldn't be significantly affected by being outdoors.
A large part of the problem is the scientific models about the spread of viral diseases were wrong. In 2019, they classified respiratory diseases as aerosolized and non-aerosolized, but in early 2020 they took a hard look at the models, and realized it's not that binary. Disease aren't simply aerosolized or not; instead, they fall along a spectrum. It's true that covid-19 is spread by large droplets, but the percentage of viral particles spread in that fashion is fairly small. Instead, it's highly aerosolized. Most of the viral load emitted by an infected person are contained in tiny particles.
This realization should have led to a radical change in the recommendations and mandates. They should have stopped emphasizing hand washing, regular cleaning of surfaces, plexiglass shields, masks, and so on. While some of those recommendations may have been still advisable because they're low impact and general good practice (like hand washing and cleaning of surfaces), they should have been deemphasized and the highly invasive or destructive ones (like mask wearing) should have been eliminated entirely.
Instead, they should have started strongly pushing ventilation. Open doors, open windows, good airflow within buildings, methods to process the air (airplane ventilation systems worked amazingly well -- zero superspreader events have happened on an airplane since the start of the pandemic), and so on. Because the tiny aerosolized particles that contain the bulk of the viral load emitted by infected persons remain airborne for hours and days. It's not the immediate projection of gooey stuff onto other people that spreads the disease, but the slow concentration of viral particles over time, which is accelerated by keeping your mouth open (this is why so many superspreader events involve talking or singing). And this only works in still air, which is why why there has been little to no spread in outdoor settings.
But they completely ignored this, and doubled down on their existing recommendations. Even when they finally officially recognized the highly aerosolized nature of the disease (the CDC didn't do this until April 2021), they still didn't change their recommendations.