Please explain this line for me: The poliovirus vaccination status of children should be evaluated periodically. Those who are inadequately protected should complete the recommended vaccination series. No additional doses are needed if more time than recommended elapses between doses (e.g., more than 4--8 weeks between the first two doses or more than 2--14 months between the second and third doses).
Especially the bolded line. Explain to me as a complete dolt and layperson what does it mean?