It's commonly known that there are numerous studies showing vaccination reduces infection, reduces infection time, and reduces transmission. It's also common sense that this would be the case. A virus isn't going to replicate and spread as well in someone who has a massive army of antibodies waiting for it (from recent infection or vaccination), compared to some dude with zero protection who is statistically at greater risk, and with a longer infectious/ transmission time.
Pfizer is seemingly the better of the protection, which is good, as that's what the kids are getting.
Vaccination still greatly reduces the risk of infecting others despite the arrival of the delta variant, recent studies show
www.newscientist.com