evidence: Vaccination providers should adhere to recommended vaccination schedules (Table 3-2). Administration at recommended ages and in accordance with recommended intervals between doses of multidose antigens provides optimal protection. [...] (e)Based on expert opinion. [...] (cc) A special grace period of 2 months, based on expert opinion, can be applied to the minimum age of 15 months when evaluating records retrospectively, which results in an acceptable minimum age of 13 months. An additional 4 days should not be added on to this grace period.