Ideally, we need an effective vaccine for persons of all ages. However, if the vaccine is in short supply, priming fi rst those persons at high risk (e.g., young children, persons >50 years of age, healthcare workers) may be justifiable. During the early stages of an emerging H5 pandemic, such persons at high risk might be given an adjuvanted vaccine produced from a currently circulating strain, even if it is antigenically distinct, until an optimally matched and approved vaccine is available. This strategy is to produce a vaccine from an antigenically distant infl uenza (H5N1) strain that could induce broad-spectrum immunity capable of neutralizing newly emerged human H5 strains.