Yes, vaccines block most transmission of COVID-19
COVID-19 vaccines have provided an opportunity to slow the spread of the virus and end the pandemic. Now scientists are trying to learn just how much the vaccines can prevent transmission from occurring at all. New data from the CDC shows that COVID-19 infections do occur in vaccinated people, but they appear exceptionally rare.
As of April 14, the Centers for Disease Control and Prevention had received reports that 5,814 fully vaccinated people had developed COVID-19 infections. Nearly half of these infections (45 percent) were in people at least 60 years old. Seven percent of people with breakthrough infections—infections that occur after complete vaccination—were hospitalized and one percent died.
With more than 85 million people in the United States fully vaccinated against COVID-19, the CDC has been cautiously expanding guidelines about what those fully vaccinated people can safely do. The expansion has been gradual as experts awaited data on not just how well the COVID-19 vaccines prevent disease, but also whether a fully vaccinated individual could develop an infection—without symptoms—and unknowingly pass the virus along to someone else.
The distinction is important because many people do not realize that vaccines primarily prevent the disease but not necessarily infection. That means not all vaccines block fully vaccinated people from transmitting the pathogen to others.
https://www.nationalgeographic.com/science/article/yes-vaccines-block-most-transmission-of-covid-19