目的   制备口服轮状病毒（rotavirus，RV）活疫苗病毒滴度评价的国家参考品。方法  选取检定合格的口服RV活疫苗原液，加入保护剂，1.0 ml/安瓿分装，冷冻干燥，制备病毒滴度参考品。用微量细胞病变法检测参考品的病毒滴度，用Karber法计算半数细胞培养感染量（50% cell culture infective dose，CCID₅₀）。由3家实验室对参考品的病毒滴度进行协同标定，采用单因素方差分析和最小显著差数法对3家实验室的标定结果进行统计学分析。另外，将参考品于-20 ℃放置1年、4 ℃放置1年、37 ℃放置14 d、-60 ℃放置2年，测定病毒滴度，分析参考品的热稳定性和长期稳定性。结果  经单因素方差分析比较，3家实验室检测结果的差异无统计学意义（F=0.379，P=0.686）。采用最小显著差数法对3家实验室检测结果的均值进行两两比较，差异亦无统计学意义（sx均为0.0782，P值均>0.05）。参考品的平均病毒滴度为6.5 lgCCID₅₀/ml，于不同温度放置一段时间后病毒滴度下降均未超过1.0 lgCCID₅₀/ml。长期稳定性试验结果的变异系数为4.9%。 结论  制备了可用于口服RV活疫苗病毒滴度检测的国家参考品。

Objective  To prepare a national evaluation reference of virus titer for live oral rotavirus (RV) vaccines. Methods  A bulk of qualified live attenuated RV vaccine was mixed with preservative, packed into ampoules (1.0 ml/vial) and lyophilized. The virus titer of the reference preparation was determined by a micro-cytopathic method and 50% cell culture infective dose (CCID₅₀) was calculated with Karber method. The reference was collaboratively evaluated in 3 different laboratories and results were analyzed by one way ANOVA and least-significant difference test. In addition, the virus titers were determined after the reference was stored at -20 ℃ for 1 year, 4 ℃ for 1 year, 37 ℃ for 14 d and -60 ℃ for 2 years, respectively.  Results  There was no significant difference among results from the 3 laboratories by one way ANOVA (F=0.379, P=0.686) or by pairwise comparison with least-significant difference test (sx=0.0782, all P values>0.05). The average titer of the reference was 6.5 lgCCID50/ml. The reduction of titer was no more than 1.0 lgCCID₅₀/ml after the preparation was stored at different temperatures for different periods. The coefficient of variation in long-time stability test was 4.9%. Conclusion  The reference prepared can be used for virus titer evaluation of live oral RV vaccines.