Post-Distribution Survey for Potency of Live Attenuated Oral Polio Vaccines (OPV) used in Sudan Northern States Peripheral Children Immunization Clinics
Post-Distribution Survey for Potency of Live Attenuated Oral Polio Vaccines (OPV) used in Sudan Northern States Peripheral Children Immunization Clinics
Elamien***, Mohammed; Kotob**, Nahla S.; Elsayed*, Eltayeb A.; Ragab, Yasser M. and Mourad, Fathia E.
ABSTRACT
National immunization days (NIDs) started in 1994 in Sudan by using trivalent OPV (topV) and in the beginning of 2010 bivalent OPV (bOPV) was permitted to be use. Since OPV is manufactured from a highly thermolabile vaccine strain of poliovirus, it should be stored under the recommended temperature of -200C or below. A vaccine vial monitor (VVM) is a label containing a heat sensitive material which is placed on a vaccine vial to register cumulative heat exposure over time. Despite Of several polio vaccine coverage campaigns in the last two years, four of five children poliomyelitis cases reported in March 2009 in northern Sudan States, came from the Red Sea State. The aim of this study is to investigate the quality Of OPV used for children immunization clinics in Red Sea State, to ensure whether the vaccine is still keeping its potency after being exposed to storage and transportation conditions. Several fixed, outreach and mobile immunization clinics were selected from all Red Sea State localities. Fifty seven bOPV samples and fifty seven topV samples were taken during NIDs campaign in February 2010 and June 2010 respectively, and their potency were tested by the determination of a cell culture infective dose 50% (CCID50) in Hep-2 Cincinnati cell line and using the Karber's Formula. All topV (type 1, 2 and 3) samples were found to be potent, within World Health Organization (WHO) normal limits. However, type-3 poliovirus in most of the bOPV (type 1 and 3) samples showed a titer lower than the WHO normal limits although all samples have at least grade Il VVMs. These data indicate that type-3 poliovirus in case of bOPV needs more investigations in spite of cold chain and grade Il VVM appear to be efficient.
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