Prospects for the eradication of infectious diseases.

The meaning of eradication, which is an irreversible conclusion, is considered primarily to distinguish it from elimination, which is reversible from outside the area. Poliomyelitis and measles are at present the diseases for which conditions most favor an attempt to produce eradication. Poliomyelitis has now reached a frequency in the developing world as high as it was in the prevaccine era of the United States. The use of oral vaccine is a deliberate attempt to substitute the wild-type polioviruses in the community with the vaccine-like viruses derived from the vaccine itself. Mass use of vaccine in all children less than five years of age on a single day twice in a year has produced a critical decrease in the incidence of the disease in Brazil. Following determined efforts to achieve immunization of at least 95% of the population, the United States is now nearing the state of complete freedom from the transmission of measles virus. The use of diploid cells for making vaccine has enabled the virus to be given as an aerosol to babies less than six months of age and would be of particular value in developing countries. The high transmissibility of measles makes a severe demand for vaccine, but so long as the uptake of vaccine reaches at least 90%, the successful elimination of measles is extremely probable.