obsolete gene true The term 'gene' has appears in several ontologies, such as Sequence Ontology (SO) and Protein Ontology (PRO). We may choose to use a 'gene' term from other ontologies. The 'gene' term in SO has ID: SO:0000704. A gene that is a pathogen gene used for vaccine preparation or a host gene encoding for an immune factor important in induction of protective immunity. a vaccine-associated gene that exists in a pathogen and has been engineered for vaccine develoment. This gene can encode for protective antigen that is overexpressed for vaccine development. This gene can also be a virulence factor that is mutated to attenuate a virulent pathogen with the purpose of making attenuated vaccine. Oliver He