Your base odds of getting corona while fully vaxxed are 1 in 15M (1/1000 current cases you must encounter and 1/15,000 chance for breakthrough infection). That's baseline. Already we're at some long odds. Unless I've missed the news I've not seen any reports of fully vaccinated people giving the virus to other people. If I'm wrong I'd be happy to see those articles. But for the sake of argument let's say it's possible. We already know the vaccine greatly reduces viral load in the unlikely event you get infected. You have a roughly 50% chance of infecting someone via prolonged close contact in a confined space. A 90% reduction in viral load from the vaccine reduces that value to 5%, 1 in 20. That gives you a 1 in 300M chance of being vaccinated, getting infected, and passing it on to an unvaccinated person you spend a prolonged period with in a confined space. This is also assuming they aren't wearing a mask, and as you've stated they are very effective so the odds would be even higher. You are 100 times more likely to die from a bee sting than for that series of events to happen.
