Stability-related studies on 17D yellow fever vaccine

Yellow fever (YF) vaccine using the 17D strain of YF attenuated virus has b een produced ar the Institut Pasteur in Dakar since 1962. Until now, the st abilised YF had an expiry date of utilisation of two years from the end of the lot control process under storage at + 4 degrees C. We conducted a stab ility study to assess the three full year validity of this preparation, whe n correctly stored at + 4 degrees C to optimise the conditions of productio n, storage and availability of such a vaccine. The activity of 19 consecuti ve batches of vaccines kept for three years at + 4 degrees C was compared t o that of the same batches that were kept three years ar: -20 degrees C, Us ing the in vitro microculture method, we found that three-year storage at 4 degrees C induced a higher loss of activity than storage at -20 degrees C or than the accelerated degradation test of vaccines kept for 14 days at 37 degrees C. Whatever the conditions of storage, in all cases decreases in activity were below the WHO's requirements, i.e., < 1 log PFU/dose, and re sidual activity of the selected batches was over 1000 mouse LD50 per dose. We demonstrated that the 17D YF vaccine produced in Dakar has a shelf-life of three years and that its required potency was maintained at + 4 degrees C, after reconstitution with saline diluent, following three-year storage a t + 4 degrees C. (C) 2000 Editions scientifiques et medicales Elsevier SAS.