BACKGROUND: The annual Georgia Immunization Study (GIS) employs a retrospective cohort research design to determine the up-to-date (UTD) immunization rate for 24-month-old children born in Georgia. We used the annual GIS data from 2014 and 2015 to quantitatively determine the reasons GA two-year-olds were not age-appropriately UTD, and to examine demographic characteristics.
METHODS: Each year the GIS utilizes a stratified random sample of children born in Georgia who become 24 months old in January. Demographic information is obtained from electronic birth records, and immunization data is obtained from the Georgia Registry of Immunization Transactions and Services. For children inadequately immunized (4:3:1:3:3:1:4 level) based on Advisory Committee on Immunization Practices recommendations, health department staff contact parents and providers to verify information and determine reasons for inadequate immunization. We compared maternal race, ethnicity, age, education level, marital status, and metro Atlanta residence variables among children who were UTD at 24 months with those of children who remained inadequately immunized six months later. Reasons for inadequate immunization were also quantified and stratified by maternal demographics. Fischer’s Exact test was used to compare proportions; p <0.05 was considered significant.
RESULTS: A total of 3500 children sampled in 2014 and 2015 were UTD by 24 months; 306 children remained inadequately immunized after follow-up. Mothers of children inadequately immunized were significantly more likely to be non-Hispanic than those who were UTD, but maternal age, race, education, marital status and metro residence were similar. Vaccine hesitancy, measured by combining religious exemption, parental refusal, and parental delay accounted for 44% of inadequate immunizations; 28% were due to missed appointments/convenience issues; 7% were for medical reasons (only 0.3% were due to medical exemption); and 21% were “other”. When stratified by maternal demographics, vaccine hesitancy was significantly more likely among two-year-old children with mothers of white race, non-Hispanic ethnicity, college-level education, age > 25 years, married status, and/or non-metro Atlanta residence. Missed appointments/lack of convenience as a reason for inadequate vaccination was significantly associated with children of mothers who were without college education, < 25 years of age, unmarried, and/or with non-metro Atlanta residence.
CONCLUSIONS: Vaccine hesitancy may account for 44% of inadequately vaccinated two-year-olds in GA. The identification of specific maternal demographics associated with vaccine hesitancy and missed appointments/convenience issues as reasons for inadequate vaccination of Georgia’s two-year-olds may be useful in targeting efforts to improve vaccination rates in this population.