County-level trends in vaccination coverage among children aged 19-35 months - United States, 1995-2008

Estimated trends in county-level vaccination coverage compared with national health objectives and associated with other variables (e.g., access to care, economic conditions, and demographic characteristics) have not been reported previously.

1995-2008.

The National Immunization Survey (NIS) is an ongoing, random-digit-dialed telephone survey that gathers vaccination coverage data from households with children aged 19-35 months in 50 states and selected urban areas and territories.

During 1995-2008, 185,336 children aged 19-35 months sampled by NIS had adequate provider data and lived in one of the 257 counties where the combined sample size for at least one of the seven biennial periods during 1995-2008 was ≥35. Statistically significant increases in estimated vaccination coverage occurred in 27 of 233 counties (12%) with ≥4 doses of diphtheria and tetanus toxoids and acellular pertussis (DTaP); for 38 of 233 counties (16%) with ≥3 doses of polio vaccine; eight of 233 counties (3%) with ≥1 dose of measles, mumps, and rubella (MMR); nine of 233 counties (4%) with ≥3 doses of Haemophilus influenzae type B (Hib) vaccine; 193 of 233 counties (83%) with ≥3 doses of hepatitis B vaccine; 228 of 232 counties (98%) with ≥1 dose of varicella vaccine; and 187 of 192 counties (97%) with ≥4 doses of 7-valent pneumococcal conjugate vaccine (PCV7). Six of 233 (2%) counties had significant decreases in vaccination coverage for Hib. During the 2007-2008 biennial period, the percentage of 193 counties with estimated vaccine coverage that achieved the Healthy People 2010 objective of 90% vaccination coverage was 8% for DTaP/DTP vaccines, 93% for polio vaccine, 86% for MMR vaccine, 71% Hib vaccine, 94% for hepatitis B vaccine, 50% for varicella vaccine, and <1% for PCV7. Among 104 counties, the estimated percentage of children aged 6-23 months who were administered ≥1 dose of the seasonal influenza vaccine during the 2007-2008 influenza vaccination season was 39.0% (range: 22.2%-68.8%). For most vaccines and vaccine series, higher levels of county-level vaccination coverage correlated with a higher number of pediatricians per capita, a higher number of people living in group quarters (e.g., college residence halls, residential treatment centers, skilled nursing facilities, group homes, military barracks, correctional facilities, workers' dormitories, and facilities for persons experiencing homelessness) per capita, higher per capita income, a higher number of Hispanics per capita, and having a service-dependent economy. Lower levels of county-level vaccination coverage correlated with higher number of persons in poverty per capita, a higher percentage of black children among children aged <5 years, higher levels of housing stress (i.e., ≥30% income for rent or mortgage and certain inadequate housing characteristics), a higher number of pediatric intensive care beds per capita, and designation as a nonmetropolitan county with an economy dependent on recreation activities.

During 1995-2008, significant increases in vaccination coverage for individual vaccines occurred in many counties for the newly recommended vaccines, varicella and PCV7.

In counties that did not meet the Healthy People 2010 vaccination coverage objectives, states should evaluate strategies to achieve these objectives. The Guide to Community Preventive Services provides a summary of interventions that increase community vaccination coverage, including provider reminder-recall systems that remind parents to return to clinics to administer missed doses to children and assessment and feedback on the performance of vaccination providers. In counties where significant decreases in Hib vaccination coverage occurred, additional research is warranted to determine whether the recent shortage in the Hib vaccine was the sole cause of these decreases. In counties with a high proportion of children living in poverty, interventions to increase vaccination coverage among these children are needed. Additional research is required to understand potential barriers to increased coverage with these vaccines, the role of vaccination providers and their resource constraints, and factors associated with access to health care among children.