The ages of 19-23 months were chosen to align with National Immunization Survey (NIS) data for benchmarking. While the NIS examines the immunization status of children up to 35 months, the AAP opted to choose a lower age limit. This is to help identify areas in practice that could be improved and lead to fewer missed opportunities. Children have the opportunity to finish the primary vaccination series by 18 months.
Some users cite that the 2 doses of Hepatitis A might not be completed by 19 months of age. This is true. The recommended schedule states that 2 doses should be completed by 23 months. In identifying this as a gap, we ask practices to see if opportunities are being missed by delaying receipt of that vaccine to later ages. Are children coming in at 12 and 15 but not 18 months and missing that vaccine?