RESUMEN
Comprehensive estimates of vaccination coverage and timeliness of vaccine receipt among American Indian/Alaska Native (AI/AN) children in the United States are lacking. This study's objectives were to quantify vaccination coverage and timeliness, as well as the proportion of children with specific undervaccination patterns, among AI/AN and non-Hispanic White (NHW) children ages 0-24 months in Montana, a large and primarily rural U.S. state. Data from Montana's immunization information system (IIS) for children born 2015-2017 were used to calculate days undervaccinated for all doses of seven recommended vaccine series. After stratifying by race/ethnicity, up-to-date coverage at key milestone ages and the proportion of children demonstrating specific patterns of undervaccination were reported. Among n = 3,630 AI/AN children, only 23.1% received all recommended vaccine doses on-time (i.e., zero days undervaccinated), compared to 40.4% of n = 18,022 NHW children (chi-square p < 0.001). A greater proportion of AI/AN children were delayed at each milestone age, resulting in lower overall combined 7-vaccine series completion, by age 24 months (AI/AN: 56.6%, NHW: 64.3%, chi-square p < 0.001). As compared with NHW children, a higher proportion of AI/AN children had undervaccination patterns suggestive of structural barriers to accessing immunization services and delayed starts to vaccination. More than three out of four AI/AN children experienced delays in vaccination or were missing doses needed to complete recommended vaccine series. Interventions to ensure on-time initiation of vaccine series at age 2 months, as well initiatives to encourage completion of multi-dose vaccine series, are needed to reduce immunization disparities and increase vaccination coverage among AI/AN children in Montana.
RESUMEN
Human papillomavirus (HPV) vaccination rates are lower in rural versus urban areas of the United States. Our objective was to identify the types of vaccination clinic settings where missed opportunities for HPV vaccine series initiation most frequently occurred in Montana, a large, primary rural U.S. state. We analyzed a limited dataset from Montana's immunization information system for adolescents who turned 11 years old in 2014-2017. Vaccination visits where the HPV vaccine was due but not administered were missed opportunities. We compared missed opportunities across six types of clinic settings, and calculated adjusted relative risks (RR) using a generalized estimating equation model. Among n = 47,622 adolescents, 53.9% of 71,447 vaccination visits were missed opportunities. After adjusting for sex, age, and rurality of clinic location, receiving vaccines in public health departments was significantly associated with higher risk of missed opportunities (aRR = 1.25, 95% confidence interval = 1.22-1.27, vs. private clinics). Receipt of vaccines in Indian Health Services and Tribal clinics was associated with fewer missed opportunities (aRR = 0.72, 95% CI: 0.69-0.75, vs. private clinics). Our results indicate the need for interventions to promote HPV vaccine uptake in public health departments, which are a critical source of immunization services in rural and medically underserved areas of the U.S.