One-dose immunization against paralytic poliomyelitis using a noninfectious vaccine.

Recent advances in production and standardization of noninfectious poliovirus vaccine now make it feasible to induce durable immunity against paralytic poliomyelitis with one dose of a suitably standardized vaccine. A single dose of a vaccine containing 40, 8, and 32 D-antigen units of type 1, 2, and 3, respectively, administered to six-month-old infants, was observed to induce antibody levels of greater than or equal to 1:4 in greater than 90% and immunologic memory in all. Since protection against paralysis is associated with the presence of either type-specific serum antibody or type-specific immunologic memory, and since immunologic memory once induced is irreversible, then lifelong immunity to paralytic poliomyelitis can be induced with a single dose of a suitably standardized vaccine administered at five to seven months of age. In areas of the world where exposure to poliovirus can occur before this age, vaccine should be administered earlier. Until the influence of age and/or maternal antibody has been further studied, infants immunized before the age of six months should receive a second dose after six months of age.