[Study on the stability of Japanese encephalitis vaccine--development of freeze-dry dosage form].

In order to prolong shelf-life and improve the quality of the vaccine product, not only an effective stabilizer but also a more proper dosage form has been sought. The stability of a Japanese encephalitis (JE) vaccine produced from mouse brain along with a variety of stabilizers and lyophilization protocols was evaluated. Without any stabilizers added, almost 90% of the antigenicity would vanish after freeze-drying process. Comparative studies of various compounds, including carbohydrates, amino acids, peptides and medium 199, on both antigenicity preservation and thermostability of the vaccine were carried out. The results indicated that the best reconstituted vaccines were prepared with two stabilizer formulations, sucrose and sucrose/gelatin. They were further examined by accelerated stability test at room and higher temperatures. The sucrose-added lyophilized vaccine can retain its original antigenicity for more than 60 days both at 37 degrees C and 45 degrees C. We conclude the thermostability efficiency of each of the stabilizers tested is as that follows: sucrose > sucrose/gelatin > gelatin/medium > gelatin.