Oral polio vaccine. Effect of booster vaccination one to 14 years after primary series.

We studied the persistence of antibody after vaccination and the response to booster revaccination with trivalent oral polio vaccine (TOPV) administered at varied intervals after the primary series in a large group of children. Decline in antibody was related to intervals since last vaccination, and not to sex, age, age at primary vaccination, or type and number of previous administrations. Geometric mean titers of neutralizing antibody were 11.3 for type 1 and 8.0 for types 2 and 3 poliovirus when vaccine had been given within the previous year, declining to 3.2, 3.0, and 2.1 for types 1, 2, and 3 after nine years. Most children with an initial titer of 4 or less responded to revaccination with a fourfold or greater increase in titer of IgG. Geometric mean titers for all three types of polio dropped to this level when last TOPV administration had been five to six years or more.