[Earlier vaccination against polio].
D000367:Age Factors; D002648:Child; D006801:Humans; D007223:Infant; D011051:Poliomyelitis / Q000517:prevention & control*; D011054:Poliovirus Vaccine, Inactivated; D014611:Vaccination
D011054:Poliovirus Vaccine, Inactivated
Tidigareläggning av vaccination mot polio.