Because they aren’t 100% effective and never have been?
Saying the Covid vax is even in the neighborhood is BS.
Smallpox and many others have a high percentage of negating illness and transmission.
Before Covid, it was always called a flu shot, not a vaccine.
It was known to not work effectively rather often.
Because they aren’t 100% effective and never have been?
**********
Vaccines don’t work for everybody. Such as people with compromised immune systems. A vaccine can sometimes be under-strength, as with the Phizer COVID shot. Or there can be bad batches. Thus, if a vaccinated person gets the disease anyway for these reasons, the disease can be transmitted.
But where the vaccine actually prevents a person from getting a disease, he can’t transmit a disease that he doesn’t have. Someone who doesn’t get polio, smallpox, measles, etc., because of vaccination cannot transmit these diseases.