After receiving a first dose, 4.5 percent of [nursing home] residents still contracted the virus, although most cases were asymptomatic, researchers wrote. Of those receiving the second dose, only 0.3 percent got the virus after 14 days. The benefit carried over to those in the same nursing homes who did not get vaccinated. Their rate of infection dropped to 0.3 percent from 4.3 percent. For all groups, most infections were asymptomatic; and the rate of both symptomatic and asymptomatic infections decreased over time.