The ImmunizationRecommendation profile constrains ImmunizationRecommendation.recommendation.supportingImmunization to just referencing QICoreImmunization where the base resource allows both Immunization and ImmunizationEvaluation. Given that a recommendation for a new immunization is typically based on the evaluation of an immunization event against a defined schedule (ie an ImmunizationEvaluation), it seems like the profile should also allow QICoreImmunizationEvaluation as a reference as well.