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Article Title

The relationship between the cold chain system and vaccine potency in Taiwan: (II) Oral polio vaccine

Abstract

The live attenuated oral poliovirus vaccine (OPV) has been used for the poliomyelitis eradication program in Taiwan for a long time. Since it is manufactured from a highly thermolabile vaccine strain of poliovirus, it should be stored under the recommended temperature of -20°C or below. This study investigated and evaluated the efficiency of the cold chain system for maintaining the polio vaccine potency in Taiwan. We selected several health stations and local hospitals/pediatric offices in each County/City of Taiwan to take the OPV samples and test their potency from Nov. 1997 to Feb. 1998. Our results showed that the type-1 poliovirus of all OPV samples met the requirements for the potency test, showing titers were higher than the criteria of the WHO and the ROC (Taiwan) national standard. The type-2 and -3 polioviruses in most of the OPV samples showed titers higher than the criteria, with the exception of a few samples. We found that the degradation of type-2 poliovirus was associated with the thawed samples, which were stored at temperatures not low enough. The factor that caused the degradation of the type-3 poliovirus was unclear so far. Nevertheless, the results of this study indicated that the cold chain system used in Taiwan was generally satisfactory for the OPV storage.

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