Immunogenicity of a pilot inactivated poliovirus vaccine with trypsin-treated type 3-component.

A modified trivalent enhanced potency IPV (E-IPV) containing trypsin-treated PV3/Saukett as the type 3-component (TryIPV) was evaluated in preclinical and Phase I and Phase II clinical trials with the regular E-IPV as a control. In Balb/c mice, TryIPV-induced antibodies targeted outside the trypsin-sensitive antigenic site, as expected. Immunogenicity of TryIPV in man, as judged by a booster response in neutralizing antibodies to type 1, 2 or 3 poliovirus, was as good as that of the regular E-IPV in both adults and children. In children the preimmunization titres of antibodies neutralizing the trypsin-treated PV3/Saukett were significantly lower than those for the untreated virus. Both vaccines induced a striking increase of antibody titres to both virus preparations. No significant harmful effects were observed. We conclude that the pilot vaccine is suitable for further evaluation.