Long-lasting poliovirus-neutralizing antibodies among Argentinean population immunized with four or five oral polio vaccine doses 1 month to 19 years previously.

The persistence of poliovirus-neutralizing antibodies was investigated in 297 individuals residing in Argentina who had completed the vaccination cycle with four or five oral polio vaccine (OPV) doses 1 mo to 19 yr before this study. Seropositivity for the three polio types in individuals who had received four OPV doses remained high and stable, showing rates not less than 94.6, 98.2, and 91.1% for types 1, 2, and 3, respectively, for a period of at least 6 yr. Almost identical rates were found in children who completed a vaccination schedule of five OPV doses 1 to 2 yr earlier. However, humoral immunity to poliovirus types 3 and 1 declined significantly 9 and 17 yr, respectively, after the booster dose had been administered; in contrast, type 2 immunity remained fairly stable during the 19-yr study period. Overall, geometric mean titer values for poliovirus types 1 and 2 were higher than those for poliovirus type 3. This is likely a result of low initial poliovirus type 3 antibody titers that eventually fell below the limits of detection at later time points. The results indicate that although antibody titers primed by OPV decline over time, they are remarkably long-lived, immunity to poliovirus types 1 and 2 being more prevalent than that against type 3 at late intervals postvaccination.