Developing gap in immunity to poliomyelitis in an urban area

Paralytic poliomyelitis reappeared in Houston in 1968 after a five-year period during which the city was free from the disease. Results of serological study indicate that in 1968 a large segment of children in low-income families were susceptible to infection by poliovirus, with as many as 62% of infants 3 to 8 months old lacking antibody against any type of poliovirus, and with 32% completely susceptible even at ages 12 to 23 months. Comparison with findings of a similar study carried out shortly after Houston's 1962 mass vaccination campaign indicates that a wide and disturbing immunity gap is developing in this sector of the population. There is clearly a need for longitudinal surveillance of polio immunity, and for concerted efforts to assure continuing vaccination of infants and young children, particularly in the lower socioeconomic group.