Randomised, controlled trial with the trypsin-modified inactivated poliovirus vaccine: assessment of intestinal immunity with live challenge virus

The enhanced potency inactivated poliovirus vaccine (E-IPV) was modified to contain trypsin-treated type 3 poliovirus (PV3), strain Saukett, as the ty pe 3 component (TryIPV), This pilot vaccine was previously shown to redistr ibute the vaccine-induced antibody specificities in mice to mimic those see n in man after poliovirus infection. Groups of infants were then immunised with three doses of TryIPV or E-IPV in a randomised, double-blind trial. Si x months after the third dose, at the age of 18 months, the children were c hallenged with one dose of oral monovalent type 3 poliovirus vaccine. Intes tinal immunity was evaluated by assessing the length and extent of PV3 excr etion through determination of PV3 titres in 9 successive faecal specimens (2-42 days after challenge). No significant difference in the length or ext ent of virus excretion was seen between the groups. The results indicate th at TryIPV, under the conditions used, was no more potent than the regular E -IPV in inducing resistance to intestinal poliovirus infection. (C) 1999 El sevier Science Ltd. All rights reserved.