Laboratory methods for assessing vaccine potency retained in aerosol outputs from nebulizers: Application to World Health Organization measles aerosol project

Background: Laboratory methods for measuring vaccine potency of nebulized aerosol are required to support clinical trials of measles aerosol vaccination. Methods: Measles vaccine containing the Edmonston Zagreb virus strain was reconstituted in sodium fluoride as tracer and nebulized from three devices. Emitted aerosol was collected using an impinger. Aliquots were removed from the impinger chamber for vaccine virus plaque assay and for fluoride measurement to determine aerosol output. Results: Vaccine potency retention results were adjusted to take into account the effect of aerosol output on estimates. Adjusted potency of nebulized vaccine ranged from 88% to 102%. Conclusions: New laboratory methods to measure aerosol vaccine potency retention were reliable and accurate. The results demonstrated that Edmonston Zagreb vaccine remains robust during aerosolisation and imply that this is a viable candidate for further evaluation in the measles aerosol project. (C) 2008 Elsevier Ltd. All rights reserved.