HLN is one of the pre-eminent immunization registry system services vendors in the country, specializing in project evaluation and continuing development of custom systems.

HLN has provided and continues to provide technical support and software development of immunization registries to several major jurisdictions, such as New York City, Rhode Island, Los Angeles, New Jersey, Philadelphia and regional projects within California.

Because of continuing work developing and support of both Microsoft-based and Open Systems-based registries, HLN hosts a unique software test bed that can be leveraged for new concepts and interfaces. No other immunization registry developer operates such a diversity of registry products and architectures.

HLN has been a sustaining member of the American Immunization Registry Association (AIRA) since 2003 and was AIRA's 2003 Partnership Award recipient.