Stability of freeze-dried and reconstituted measles vaccines.

The stability of the titer of live vaccines is a very important factor for successful immunization, especially in countries with a hot climate. For the freeze-dried vaccine, the results of stability tests show that the second generation Rimevax possesses the desired resistance to thermodegradation. In the refrigerator, the shelf life is at least 2 years. Exposure at 20--25 degress C for 1 month, at 37 degrees C for 7 to 14 days or at 41 degrees C for 3 to 7 days results in a vaccine retaining its full immunogenic activity. The value of an accelerated stability test at 37 degrees C for 7 days for the prediction of the potency of each lot is proven. This test should be part of the minimum requirements for live vaccines. The potency of reconstituted measles vaccines is evaluated. Rimevax shows a remarkable stability at higher temperatures. At 37 degrees C, the immunogenic activity is retained for 2 to 3 hours. Reconstitution with diluent at 41 degrees C and subsequent exposure to this temperature does not affect the titer significantly during the first half hour. The comparison of published stability data of measles vaccines shows that Rimevax is one of the most thermoresistant preparations.