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Abstract

Taiwan has a long history of using vaccines in order to protect people against certain infectious diseases. Several types of vaccines have been used successfully for protecting children from poliomyelitis, measles, and other acute infectious diseases. However, for the monovalent measles vaccine (MV), and the trivalent measles-mumps-rubella combined vaccine (MMR vaccine) which are made from live attenuated viruses, they are unstable unless stored at a proper low temperature, at a certain pH level, in darkness, and combined with some specific stabilizers. Maintaining these live virus vaccines at the recommended temperatures of +2 to +8°C is one of the most important limiting factors in this respect, particularly in a subtropical climate such as in Taiwan. This study investigated and evaluated the vaccine cold chain system at different storage levels, and selected several health stations and local hospitals/pediatric offices in each County/City of Taiwan to take samples of the MV and MMR vaccines and test their potency during the autumn of 1997. Our results show that all of the MV samples meet the requirements for the potency test, showing titers higher than the criteria of the WHO and the ROC (Taiwan) national standard. The MMR vaccine also maintained its potency, with the exception of a few mumps vaccines. This study found that the shorter the remaining term of validity (RTV) of MMR vaccines is, the more inactivation of the mumps virus could occur. The reason why the mumps vaccine of MMR vaccine seems unstable in Taiwan needs further investigation. Nevertheless, the results of this study reveal that the cold chain system used in Taiwan is satisfactory for vaccine storage.

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