Vaccines administered intradermally protect against multiple diseases.

As the number of investigational and approved vaccines continues to increase, the frequency of vaccinations will soon reach a practical limit. The development of combination vaccines is a common practice that addresses the concern of repeated visits to the clinic by reducing the total number of injections required compared with administration schedules for the monovalent vaccines. Yet, physical, chemical, and biological interactions among the components of combination vaccines must be considered to avoid detrimental effects on safety or efficacy. For example, when the Haemophilus influenzae type b (Hib) vaccine was combined with diphtheria, tetanus, and acellular pertussis vaccine, a decrease in antibody titer for the Hib vaccine was observed. Thus, there is a need to develop new approaches for delivery of multiple vaccines.