Immunogenicity of fractional-dose of inactivated poliomyelitis vaccine made from Sabin strains delivered by intradermal vaccination in Wistar rats.

Reducing the amount of antigen is an important strategy to resolve the present shortage of IPV supply for global polio eradication. In the study, we compared the immunogenicity of adjuvanted and non-adjuvanted fractional-dose of IPV made from Sabin strains (sIPV) by intradermal (ID) administration versus the full-dose of sIPV by intramuscular (IM) administration in rats by comparing seroconversion rates and geometric mean titers (GMTs) of neutralizing antibodies (NAbs). We found that, after the full 0, 1, 2 months schedule immunizations, the seroconversion rates in all groups reached 100% except non-adjuvanted 1/6 dose group. After 2 immunizations, the seroconversion rates in all the adjuvanted fractional-dose groups and the full-dose group reached 100%. The GMTs of NAbs induced by adjuvanted 1/12 fractional-dose and full-dose of sIPV were similar and dynamics of the antibody responses were consistent. We proves that the Th1/Th2 balance was not changed by the administration route by comparing ratios of the IgG subclass. Our study confirms that ID administration could reduce the required amount of antigens, the adjuvanted fractional-dose resulted in earlier and higher antibody response for all serotypes than that of non-adjuvanted fractional-dose, and the NAbs responses elicited by 1/12 dose was comparable to that by full-dose of sIPV.