Immune response of infants to fractional doses of intradermally administered inactivated poliovirus vaccine

Seventy eight infants aged 6-8 weeks received either two doses of 0.1 ml of inactivated poliovirus vaccine (IPV) intradermally 8 weeks apart (group A) or three doses 4 weeks apart (group B). Pre- and 4 weeks post-immunization serum samples were tested for the presence and titer of neutralizing antibody to poliovirus types 1, 2 and 3. The seroconversion rates to poliovirus types 1, 2 and 3 were 90, 70 and 97%, respectively, among infants in group A and 90, 80 and 98%, respectively, in group B; in children without pre-existing maternal antibody, seroconversion rates were 100% to all three poliovirus serotypes in both groups. These rates were comparable to those in children receiving five doses of OPV or two doses of intramuscular IPV. Intradermal administration of fractional doses of IPV may be a less expensive alternative for use in developing countries.