Immunization registries contain complex algorithms that predict which immunizations are valid and which are indicated for future administration to a patient. Immunization information systems and electronic medical records systems use these algorithms to provide decision support services in their applications.

HLN has extensive knowledge and expertise in developing several computerized algorithms that perform this function. Though the algorithm logic is fairly standard based on ACIP guidelines, certain jurisdiction-specific rules may be imposed based on local decisions or needs.

HLN is active in HL7's Clinical Decision Support Technical Committee Decision Support Service Project (DSS) which is working to define standard Web Services interface specifications for an immunization forecast service.