How many infective viral particles are necessary for successful mass measles immunization by aerosol?

OBJECTIVES: This study characterized the performance of the "Classical Mexican Device", which immunized 4 million children against measles, demonstrating the efficacy of aerosol vaccination.

METHODS: Using plaque-forming units to quantify virus, the particle size distribution (Next Generation Pharmaceutical Impactor) and rate of output coupled with age specific patterns of breathing allowed the calculation of expected pulmonary deposition.

RESULTS: The estimated immunization dose for infants was 30 pfu's, for small children 50, and for older children and adolescents it was 130 and 225, respectively.

CONCLUSIONS: These performance characteristics can be used to develop newer battery operable devices that are licensable.