Oral poliovirus vaccine: history of its development and use and current challenge to eliminate poliomyelitis from the world

Abstract

Oral poliovirus vaccine (OPV) is like no other live virus vaccine used in humans: vaccine strains multiply extensively in the intestinal tract, are widely disseminated in the family and community, and immunize a large proportion of the unvaccinated population. Dur-ing the search for optimal strains for vaccine use, motor neurons in the spinal cord of chimpanzees (and by extrapolation those of humans) were found to be much more resis-tant to polioviruses than those of monkeys; the reverse was true for the alimentary tract. Various biologic properties of polioviruses also varied quantitatively over a wide spec-trum and were genetically distinct. The phenomenon of somewhat increased neuroviru-lence for monkeys, but not for chimpanzees, encountered in excreted virus was exten-sively studied in families, in children's homes, and finally among hundreds of thousands of susceptible children and adults in areas where only 50 % of the susceptible population received OPV; these studies did not reveal evidence of danger. During the past 20 years "-'5million cases of paralytic poliomyelitis were probably prevented by OPV in predom-inantly temperate-climate countries inhabited by "-'2 billion people. OPV has also been used less extensivelyand not optimally in many tropical and subtropical countries, wher