It depends on the virus and the vaccine. We'll have to wait for further data on this vaccine candidate. The Salk polio vaccine does not prevent infection in th

It depends on the virus and the vaccine. We'll have to wait for further data on this vaccine candidate. The Salk polio vaccine does not prevent infection in the digestive tract, so you can still spread the virus, but it does prevent the virus from spreading beyond the digestive tract and causing paralysis. You could imagine something similar happening with a SARS-CoV-2 vaccine: that it would block infection in the lower respiratory tract but not the upper respiratory tract, allowing you to spread it by coughing and sneezing while never getting severe respiratory issues.