Two years post marketing oral poliomyelitis vaccine [OPV] evaluation during national immunization days

ABSTRACT

To measure, monitor and document the potency of oral poliomyelitis vaccine samples and their storage conditions in the field over two years period during National Immunization days [NID5]. years 2002 and 2003. 115 post marketing OPV vaccine samples were received at NRA-NODCAR from 13 different Egyptian Governorates [central stores and Primary Health Unit [PHU] stores] as well as VACSERA stores, during national immunization campaigns. All OPV samples returned from the field [PMS samples] were retested for potency [total virus content] in parallel with those kept at NRA stores, utilizing tissue culture techniques in 96-well microtitre plates. The results of the present study showed the possibility of cold chain defect at two sites, one of which the titre was still higher than WHO recommended minimum potency level 10 6.23 CCID[50]/0.1 ml. 11.3% of OPV samples showed also border line results but titre drop did not exceed 0.5 log[10] CCID[50] [P>0.05]. The second year, with the improvement of cold chain and the use of vaccines of higher potency, all OPV samples showed satisfactory results. This study emphasizes that good quality vaccines and proper maintenance of cold chains are key factors for the success of national immunization programmes