From everything we know so far, it’s highly unlikely that vaccines that are 95 percent effective at preventing symptomatic disease would have no impact whatsoever on infection. Data from animal studies and vaccine trials suggests that vaccination reduces asymptomatic infection, as well as the amount of virus produced in people infected. In Israel, where a substantial portion of the population has been vaccinated, there has been a significant decline in cases since vaccination began in December, with a 49 percent decrease observed in people over age 60, according to a preliminary report. Studies to better determine the impact of vaccines on transmission are ongoing, and in the meantime, if precautions like masking are paired with increasing immunization, SARS-CoV-2 cases should plummet.
Historical evidence shows that vaccines that do not prevent virus infection can still stop epidemics in their tracks. The polio vaccine developed by Dr. Jonas Salk, which does not provide sterilizing immunity, resulted in the rapid elimination of polio in the United States beginning in the 1950s. People lined up eagerly to receive the vaccine to protect their children and themselves. The Salk vaccine was highly protective against the devastating impact of the disease and also worked to reduce spread of the virus because so many people were vaccinated and could clear their infection.