Thank you for your inquiry about CMS117v12: Childhood Immunization Status. The denominator criteria for this measure requires those children who turn 2 years of age during the measurement period and a qualifying encounter during the measurement period. Qualifying encounters are defined by the codes from the measure's value set and performed during the measurement period. An encounter documented by an RN or LPN are qualifying documentation, for evaluating denominator compliance given the criteria above is met and documented in an EHR.