Will the COVID vaccine prevent me from infecting others?
Increasing evidence suggests that a person who has been vaccinated is less likely to infect others.
Two studies released in February pointed in this direction. The first study looked at viral load — the amount of SARS-CoV-2 virus in a person's nose and throat, which can be spread to others. The study found that the higher a person's viral load, the more likely they were to spread the infection; the lower a person's viral load, the less likely they were to spread the infection. Results from the second study suggested that people who became infected with SARS-CoV-2 after getting a COVID vaccine had a lower viral load than people who were infected but had not had a COVID vaccine. Taken together, the studies suggest that the COVID vaccine protects against both infection and transmission.
A study published in March 2021 showed that people who received an mRNA vaccine had significantly less risk of asymptomatic infection than people who were unvaccinated. This is important because people who are infected but never go on to develop symptoms are responsible for an estimated 24% of SARS-CoV-2 transmission.
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.
https://www.health.harvard.edu/covid-19/covid-19-vaccines
