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

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.

Estimating Vaccine Hesitancy in Colorado by Using Immunization Information System Data

OBJECTIVES

Vaccine hesitancy is a complex issue that threatens global health. We used data from the Colorado Immunization Information System (CIIS) to quantify vaccine hesitancy.

METHODS

We examined immunization records from CIIS for patients age 2 up to 9 months to estimate vaccine hesitancy by tabulating the number of doses received per visit and comparing it with the number of expected doses based on recommendations of the Advisory Committee on Immunization Practices. We calculated the percentage of patients in each vaccine hesitancy group who were up to date on the 7-antigen series by age 35 months. We examined the distribution of vaccine-hesitant populations among vaccination providers who report to CIIS to estimate the difference in vaccine-hesitant patient populations among vaccination providers in Colorado.

RESULTS

Of 201 450 patients, 5147 (2.6%) consistently limited the number of shots received at each visit as compared with recommendations from the Advisory Committee on Immunization Practices; 166 927 (82.9%) patients did not limit the number of shots received; 5693 (2.8%) limited the number of shots received at >1 visit but not all visits; and 23 683 (11.8%) limited the number of shots received at only 1 visit. We found differences in vaccine hesitancy distributions among certain Colorado vaccination providers.

CONCLUSIONS

Immunization information system data, although sometimes incomplete, offer an opportunity to investigate state-level vaccine hesitancy. Areas of future research include performing similar analyses over time and determining geographic and socioeconomic factors that contribute to vaccine hesitancy.

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.