Global eradication of poliomyelitis: reinvent the wheel or use existing options effectively?

The development of serum and nasopharyngeal antibody response, and the magnitude and temporal pattern of fecal shedding of vaccine and revertant polioviruses was examined in infants previously immunized with one or more doses of oral poliovirus vaccine (OPV), enhanced-potency inactivated poliovirus vaccine (EIPV), or both. The fecal samples were collected at different intervals after the last OPV dose. The nucleic acid sequences of the purified RNA obtained from all virus isolates were examined in the 5' noncoding region by dideoxysequencing to determine whether the viruses shed represent revertants (vaccine), nonrevertants, or both. The frequency and duration of vaccine virus-shedding appeared to be similar in both immunization schedules. Revertant virus shedding was not demonstrated 30 days after immunization with OPV alone. However, shedding of revertants was detected for as long as 60 days in some subjects previously immunized with EIPV. The duration of shedding of revertant virus differed with different serotypes and different immunization regimens. Prior immunization with one or more doses of OPV reduced the length of shedding of revertant virus. Significantly, however, prior immunization with one or more doses of EIPV was not associated with reduced shedding of revertant virus types. The nature of serum immune response as determined by ELISA or neutralizing antibody appeared to be similar after either immunization schedule, although the antibody titers were quantitatively higher after two doses of IPV than observed after a similar schedule with OPV. Highest antibody activity was detected in subjects immunized with a combination of IPV followed by OPV. ELISA antibody activity in the nasopharynx was regularly detected after either form of immunization.(ABSTRACT TRUNCATED AT 250 WORDS)