Herd effect and virus eradication with use of killed poliovirus vaccine

Use of killed poliovirus vaccine reliably provides protection against paralysis in individuals and can reduce the transmission of poliovirus in communities to the point of eradication. In some countries improved hygienic conditions have blocked the fecal-oral spread of poliovirus as indicated by a shift in the age distribution and the occurrence of epidemic outbreaks of poliomyelitis. In these countries pharyngeal spread is the principal means of poliovirus transmission, and it is effectively blocked by use of killed poliovirus vaccine. In countries where poliomyelitis is endemic the fecal-oral route of spread may play a more significant role; it remains to be seen if there will be an epidemiologic effect from the reduction in fecal virus excretion that is associated with high levels of serum antibody induced by potent killed poliovirus vaccine. Nevertheless, killed poliovirus vaccine will prevent paralysis in individuals in countries where poliomyelitis is endemic, and it can prevent the disease from becoming epidemic as hygienic conditions improve.