ImmunizationEvaluation.targetDisease currently has a cardinality of 1..* which is probably because this is the cardinality that targetDisease had as part of Immunization.protocol in Release 3 and before. We should consider changing the cardinality to 1..1 so that each evaluation can only relate to a single targetDisease. For example, the Twinrix vaccine contains antigen for both HepA and HepB. The dose could need to be evaluated sepearately against schedules for both diseases and it may confuse implementers if mulitple diseases can be named in targetDisease. We can restrict it in profiles, but someone may implement before we have reason to produce a profile.