Polio vaccination can protect people against naturally occurring polioviruses and vaccine-derived polioviruses. It is unlikely that a vaccine-derived poliovirus would become widespread, because most people in the United States have received polio vaccinations. Most vaccine-derived polioviruses disappear over time without causing any clinical disease. Very rarely, usually in communities where routine polio immunization has been low, vaccine-derived polioviruses have spread beyond close contacts.
Over the past decade, more than ten billion doses of oral polio vaccine have been given worldwide, with only six outbreaks of circulating vaccine-derived polioviruses confirmed, resulting in approximately 50 cases of paralytic polio. People who are not up to date with polio immunizations should talk with their healthcare provider.