||There are two general ways in which
immunization coverage is measured: (1) age appropriate and (2) up-to-date.
Age appropriate vaccination measures the proportion of children who received
the recommended vaccines at (or close to) the time when these vaccines are
due. Up-to-date vaccination measures the proportion of children who have
received all of the recommended vaccines by a certain age (i.e., age 24
months). Up-to-date vaccination can overlook periods of time when a child is
left vulnerable to diseases. For example, if a child received the MMR
vaccine at age 20 months, when measuring coverage at 24 months, the child is
considered up-to-date. Yet, this child was vulnerable to these diseases for
a significant time period. Additionally, up-to-date measures of coverage
will typically include vaccines that are administered too early and not
properly spaced between doses in the series, which may impact the protection
the child has to these diseases.