COVID-19 vaccines – Harvard Health

However, the Delta variant (now the dominant variant in the US) is more capable than the original virus of getting into cells that line the nose, mouth, and throat. Once these variants get inside the cells, they rapidly make copies of themselves, increasing what is called the viral load. That’s why even people who are fully vaccinated can carry greater amounts of the Delta variant, making it more likely that they could spread the virus to others.

Source: COVID-19 vaccines – Harvard Health