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[Expanded Programme on Immunization: stability of freeze dried measles vaccine] Programme Elargi de Vaccination: stabilite du vaccin antirougeoleux lyophilise.
Weekly Epidemiological Record / Releve Epidemiologique Hebdomadaire. 1981 Jun 12; 56(23):177-9.This report brings up to date those data summarized previously regarding the stability of freeze-dried measles vaccine and is based on information obtained from the London School of Hygiene and Tropical Medicine. The World Health Organization (WHO) intends to establish a requirement for the stability of freeze-dried measles vaccine, and a draft of such a requirement is represented along with an analysis of how such a requirement would influence WHO acceptance of the vaccine included in this report. A plaque assay method was used to determine the potency of measles vaccine which had been stored in a freeze-dried state at 37 degrees Centigrade for varying intervals. Vaccine containers were exposed at 37 degrees Centigrade in a water bath and duplicate samples transferred to -70 degrees Centigrade at intervals ranging from 1 to 28 days. The residual infectious virus was determined by the plaque assay method in parallel with vaccine that had not been incubated. The results from 16 patches produced by 9 manufacturers are summarized in a table, which includes recent data a well as the results from the previous report. 2 criteria of stability are included: the number of days required for the live virus titer to drop to an acceptable minimum level when stored at 37 degrees Centigrade (Criterion 1); and the loss of live virus titer when stored for 7 days at 37 degrees Centigrade (Criterion 2). Neither criterion is sufficient on its own. A quite unstable vaccine might still have the required potency after being stored for a week at 37 degrees Centigrade if the vaccine had a high virus titer initially. Yet, a product with satisfactory stability might still fail the potency requirement if its initial virus titer was borderline. A figure shows how the vaccines would be rated according to the proposed requirements. The proposed requirement for the stability of freeze-dried measles vaccine will be presented to the Expert Committee on Biological Standardization during its meeting in September 1981. If accepted, it would become effective by March 1982.