How are masks 99% effective against the seasonal flu, but not nearly as effective against COVID-19?
Pre-covid studies were mixed as best, but many found that asymptomatic mask wearing wasn't significantly effective at reducing flu infections.
You are really only contagious with the flu for a day before symptoms show up (and even then you aren't that contagious until the symptoms get worse).
We'd eliminate the flu spreading by just self-quarantining after the onset of flu symptoms + wearing a mask when sick to go essential things like showing for essentials or going to the drug store.
I would have thought we learned something from the pandemic about staying home when sick. But when my wife's work found out she had covid symptoms it was STAY HOME. But the tests confirmed it wasn't covid--just a cold--COME IN. Now the whole office has a cold. They learned nothing.
And masks aren't ineffective against COVID-19. Everyone wearing a mask does a pretty good job at preventing the spread of disease. However, there are a lot of people that aren't as strict about following mask rules and guidelines.
If there is, in addition, a partial immunity, e.g. from a former flu infection, the threshold for the necessary viral load to cause a disease is even higher. Which is why masks are usually more effective against the flu.
Will your immune system buildup up defences before the virus doubles to unstoppable overwhelming numbers. So a smaller starting initial number of the virus, gives the immune system a much longer time to organize.