Freeze-Drying of Monovalent Rotavirus for Use as a National Vaccine Reference Standard

Abstract

A vaccine production process generally has a high degree of variability. So, the quality control of vaccines requires reference materials for vaccine quality testing. Thailand will include a rotavirus vaccine in its Expanded Programme on Immunization soon. The certification of lot release is necessary to support the quality, efficacy and safety control of a vaccine. The National Control Laboratory (NCL) requires a vaccine reference standard, but currently there is no international reference material for rotavirus vaccine. So, in order to certify the lot release for all lots of the vaccine using the same standards, this study aimed to freeze-dry monovalent rotavirus for use as a national vaccine reference. It was conducted by using viral propagation on cell culture to have enough viral load and a freeze-drying process. Then the prepared vaccine reference standard was checked for physical characteristics, moisture content, and potency as well as other related parameters, to test stability of vaccine in accelerated conditions compared with that in a normal condition at -70°C. The test results showed that the it had good physical characteristics, a low residual moisture content of 0.52%, the coefficient of variation (CV) of packing of 0.23%, reconstitution time less than 1 minute, and a pH value 7.76; and the vaccine was free of bacterial, fungal and mycoplasma contamination. The potency values of vaccine after drying were 7.14 logCCID₅₀/0.5 ml. The average potency of over 6 logCCID₅₀/0.5ml, which conform to the requirements of vaccine manufacturers. In addition, when evaluating the homogeneity of the vaccine in different vials according to the requirements for reference material producers (ISO Guide 34:2009), it was found that the mean value was 7.34 logCCID₅₀/0.5ml with the CV of 2.34% (p=0.298). The preliminary assessment showed that all parameters were within the standards. The stability test of the vaccine in accelerated conditions at -20, 4, 20, 37 and 45°C after storage for 1, 2, 3, 4, 6, 8 and 12 weeks showed that the vaccine stability was still high at 45°C for 2 weeks and at 37 °C for 6 weeks. Moreover, after being stored at -20, 4 and 20oC, the vaccine’s potency values were not different from those at -70°C for up to 12 weeks. The stability of the monovalent rotavirus vaccine reference standard in accelerated conditions is greater than ever before. Thus, it is confirmed that the vaccine reference standard can be used for this quality control purpose. However, the vaccine potency has to be periodically monitored at the set storage temperature in a manner similar to that for other vaccine reference standards.