The association of poverty and low immunization rates in ZIP code areas. A retrospective survey of Minnesota kindergartners.

This study evaluated indicators of poverty in Minnesota ZIP code areas with low childhood immunization rates. During 1996-1997, a retrospective survey of 68,639 Minnesota kindergarten children was conducted; 68% received four doses of diphtheria, tetanus, and pertussis vaccine, three doses of polio vaccine, and one dose of measles, mumps, and rubella vaccine (4:3:1) by 24 months of age. Of 447 ZIP codes further evaluated, 24 (5%; 13 urban and 11 rural) had 4:3:1 immunization rates at 24 months of < or = 50%. None of 159 ZIP codes in which < 5% of residents were below the poverty line had immunization rates < or = 50%, compared with 9 (32%) of 28 ZIP codes with > or = 15% of residents below the poverty line (p < 0.001). Immunization rates were lowest in ZIP codes with a lower median family income and greater proportion of residents below the poverty line. Surveys such as this can help immunization programs target and monitor prevention activities for these pockets of need.