Q: Is it still possible to transmit the virus to others after you are vaccinated? And if so, does one need to still wear a mask? I have heard both opinions on this topic.
Initially, the vaccines were given Emergency Use Authorization (EUA) based on their efficacy at preventing disease (COVID-19) in the recipients of the vaccine. Studies later showed that they were also effective at reducing transmission and preventing infection in others with 91% efficacy. These studies were performed before the emergence of the delta variant and also early after initial vaccines doses were administered. Because of the emergence of the delta variant and also perhaps because of additional time passing, current studies place the efficacy of the vaccine to prevent spread of infection at 66%. So it is possible to transmit the virus to others after you are vaccinated but it is less likely than not being vaccinated. Because we seldom depend on only one intervention in public health, it would be wise to follow current recommendations with regards to wearing masks even if you are vaccinated.