With the arrival of the Delta variant, many people wondered if current vaccines lower the risk of spreading the virus to other people. This is the difference in “contagiousness” when comparing vaccinated and unvaccinated people. This question is distinct from overwhelming evidence that these vaccines effectively lower risk of hospitalization, need for critical care, and early death due to COVID.
Vaccinated people are less likely to have the virus in the first place
A new article reviewing the current evidence concluded that, “vaccinated people are not as likely to spread the virus as the unvaccinated.” In the United States, more than half of the population is fully vaccinated. The unvaccinated population is the source for most virus transmission between individuals. It is true that, like unvaccinated people, vaccinated individuals can get and transmit COVID. However, vaccinated people are far less likely to have the virus to start.
We know that vaccines provide the best protection against infection. If someone is not infected, they cannot spread the virus to others. Also, people who have been vaccinated and contract a breakthrough infection are contagious for less time compared to unvaccinated people. This is due to a smaller viral load. Recent data from New York City showed that more than 96% of COVID-19 cases are among the unvaccinated. Additionally, only 0.33% of fully vaccinated people in New York have been diagnosed with COVID.
More vaccinated people equals more protected
This is the logic behind vaccine mandates. Attending events that exclude unvaccinated people is safer than attending events that are open to all. When more people get vaccinated, this helps keep everyone else (including children and others ineligible for vaccination) safe as well. There is also evidence that if a breakthrough infection does occur in a vaccinated person, the vaccines reduce the risk of long COVID.