Identification of Spatial Clusters of Undervaccination Patterns Among Children Aged <24 Months Using Immunization Information System Data, Montana, 2015-2019.

OBJECTIVE: Spatial clustering of undervaccination leads to increased risk of vaccine-preventable diseases. We identified spatial clustering of undervaccination patterns among children aged <24 months in Montana. METHODS: We used Montana's immunization information system data to analyze deidentified vaccination records of children aged <24 months born from January 2015 through November 2017. We measured 3 outcomes that were not mutually exclusive: not completing the combined 7-vaccine series by age 24 months, having an undervaccination pattern indicative of parental hesitancy, and having an undervaccination pattern indicative of structural barriers to timely vaccination. Using geomasked residential addresses, we conducted separate Bernoulli spatial scans with a randomization P < .01 to identify spatial clusters consisting of ≥100 children for each outcome and calculated the relative risk of having the undervaccination pattern inside versus outside the cluster. RESULTS: Of 31 201 children aged <24 months included in our study, 11 712 (37.5%) had not completed the combined 7-vaccine series by age 24 months, and we identified 5 spatial clusters of this outcome across Montana. We identified 4 clusters of undervaccination patterns indicative of parental vaccine hesitancy, all in western Montana. The cluster with the largest relative risk (2.3) had a radius of 23.7 kilometers (n = 762 children, P < .001). We also identified 4 clusters of undervaccination patterns indicative of structural barriers, with 3 of the largest clusters in eastern Montana. CONCLUSION: In Montana, different strategies to increase routine and timely childhood vaccination are needed in distinct areas of this large and predominantly rural state. Immunization information system data can pinpoint areas where interventions to increase vaccination uptake are needed.

Geographic proximity to immunization providers and vaccine series completion among children ages 0-24 months.

OBJECTIVES: In the U.S., vaccination coverage is lower in rural versus urban areas. Spatial accessibility to immunization services has been a suspected risk factor for undervaccination in rural children. Our objective was to identify whether geographic factors, including driving distance to immunization providers, were associated with completion of recommended childhood vaccinations. METHODS: We analyzed records from Montana's immunization information system for children born 2015-2017. Using geolocated address data, we calculated distance in road miles from children's residences to the nearest immunization provider. A multivariable log-linked binomial mixed model was used to identify factors associated with completion of the combined 7-vaccine series by age 24 months. RESULTS: Among 26,085 children, 16,503 (63.3%) completed the combined 7-vaccine series by age 24 months. Distance to the nearest immunization provider ranged from 0 to 81.0 miles (median = 1.7; IQR = 3.2), with the majority (92.1%) of children living within 10 miles of a provider. Long distances (>10 miles) to providers had modest associations with not completing the combined 7-vaccine series (adjusted prevalence ratio [aPR]: 0.97, 95% confidence interval [CI]: 0.96-0.99). After adjustment for other factors, children living in rural areas (measured by rural-urban commuting area) were significantly less likely to have completed the combined 7-vaccine series than children in metropolitan areas (aPR: 0.88, 95% CI: 0.85-0.92). CONCLUSIONS: Long travel distances do not appear to be a major barrier to childhood vaccination in Montana. Other challenges, including limited resources for clinic-based strategies to promote timely vaccination and parental vaccine hesitancy, may have greater influence on rural childhood vaccination.

Evaluating vaccination coverage and timeliness in American Indian/Alaska Native and non-Hispanic White children using state immunization information system data, 2015-2017.

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.

Missed opportunities for human papillomavirus vaccine series initiation in a large, rural U.S. state.

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.

Timeliness of Early Childhood Vaccinations and Undervaccination Patterns in Montana.

INTRODUCTION: Early childhood vaccination rates are lower in rural areas than those in urban areas of the U.S. This study's objective is to quantify vaccine timeliness and the prevalence of undervaccination patterns in Montana and to measure the associations between timeliness and series completion by age 24 months. METHODS: Using records from January 2015 to November 2019 in Montana's centralized immunization information system, days undervaccinated were calculated for the combined 7-vaccine series. Undervaccination patterns indicative of certain barriers to vaccination, including parental vaccine hesitancy, were identified. Using multivariable log-linked binomial regression, the association between timing of vaccine delay and not completing the combined 7-vaccine series by age 24 months was assessed. Analyses were conducted in March 2020-August 2020. RESULTS: Among 31,422 children, 38.0% received all vaccine doses on time; 24.3% received all doses, but some were received late; and 37.7% had not completed the combined 7-vaccine series. Approximately 18.7% had an undervaccination pattern suggestive of parental vaccine hesitancy, and 19.7% started all series but were missing doses needed for multidose series completion. Although falling behind on vaccinations at any age was associated with failing to complete the combined 7-vaccine series, being late at age 12-15 months had the strongest association (adjusted prevalence ratio=3.73, 95% CI=3.56, 3.91) compared with being on time at age 12-15 months. CONCLUSIONS: Fewer than 2 in 5 Montana children were fully vaccinated on time for the combined 7-vaccine series. To increase vaccination rates, initiatives to increase vaccine confidence and remind parents to complete vaccine series are needed.