ABSTRACT
We conducted a clinical trial to assess an immunization schedule combining oral [OPV] and inactivated poliovirus vaccines [IPV] in infants residing four rural communities in Abu Homos district, Beheira Governorate, Egypt. Infants in group "A" received OPV during their first month and at 2, 4 and 6 months of age. Infants in group "B" received OPV during their first month and 2 months followed by both OPV and IPV at 4 and 6 months of age [combined-schedule group]. The OPV vaccine is manufactured by Egyptian Organization for Biological Products and Vaccines [VACSERA] in Egypt while the IPV is a product of Pasteur Merieux [France]. Adverse events were monitored for three days after each dose. Blood was collected before immunization and 4 weeks after each dose to assess vaccine specific serological response. A total of 163 infants received 3 correct doses, had inter-dose intervals within the allowable range and provided 4 samples of blood, were included in the per protocol analysis [85 in group "A" and 78 in group "B"]. There was no statistically significant intergroup difference in the percentage of subject reporting the primary safety endpoint [diarrhea, vomiting, fever, irritability or local reactions at the site of IPV injection] during the 3-day after each dose. There was a statistically significant greater reporting of ill feeling in group "A" after dose I and II [p<0.001] compared to group "B". All infants in the two groups acquired protective immunity, determined as possession of neutralizing antibodies at titre > 1:8 after completing vaccination. However, the geometric mean titres to each poliovirus type were significantly higher in vaccinees in group B [p<0.001]. Seroconversion rates [> 4-fold rise in titre] to each poliovirus type were high in the two treatment groups after the last dose. Difference in seroconversion rates between the two treatment groups was not statistically significant. These finding demonstrated that the combined use of OPV and IPV didn't improve immunogenicity over the use of OPV alone. The study protocol and subject-informed consent were approved by independent Ethics Committee of the participating institution [VACSERA] and the National Organization for Drug Control and Research [Egyptian National Regulatory Authority]. The study was conducted according to the Declaration of Helsinki and the International Conference on Harmonization for Good Clinical Practice. Written informed consent was obtained from all subjects prior to conducting study-related procedures