WHO Guidance: Pediatric Age Groups Term newborn infants (0-27days) Infants and toddlers (28 days to 23 month (2 -11 years Adolescents (12 to 16-18 years") υs16 years/EU18 years childrens Hospital of Fudan Ur F1964)】201WHO Guidance: Pediatric Age Groups Term newborn infants (0 - 27 days) Infants and toddlers (28 days to 23 months) Children (2 - 11 years) Adolescents (12 to 16-18 years*) *US 16 years/ EU 18 years