Socioeconomic Disparities Persisted Alongside Improving Vaccination Rates In US Over 11-Year Period


Findings indicating that socioeconomic disparities widened gaps in vaccination timeliness signal the need for increased efforts to promote timely vaccination among children from families with lower income and those without private insurance.

Although the number of children aged 0 to 19 months in the US receiving on-time vaccinations increased between 2011 and 2021, disparities in vaccination timeliness by socioeconomic factors became exacerbated within the same period, according to new research published in JAMA Network Open.1

Infant receiving vaccination / Marina Demidiuk -

Infant receiving vaccination / Marina Demidiuk -

While the US Advisory Committee on Immunization Practices has established an immunization schedule detailing which vaccinations should be provided at what age to children, the timeliness of vaccine receipt has not been surveilled. This data is crucial for several reasons: delays in receiving vaccinations can raise the risk of vaccine-preventable diseases like measles and whooping cough, and children who do not keep pace with the vaccination schedule are less likely to receive vaccinations that require multiple doses. What’s more, tracking the timely receipt of preventive care is essential for assessing progress toward eliminating disparities in children’s health.

Key Takeaways

  • Despite an overall increase in on-time vaccinations among children aged 0 to 19 months in the US between 2011 and 2021, the socioeconomic gap in timely vaccinations widened.
  • Children from wealthier families and those with private insurance increased on-time vaccinations by a larger margin than children from families with lower income or with Medicaid coverage.
  • Based on current study findings, investigators called for novel approaches to ensure timely vaccinations for children from families with lower income.

To provide insight into this area, investigators in the current study used data from the annual National Immunization Survey-Child (NIS-Child) between 2011 and 2021 to measure vaccination timeliness of the combined 7-vaccine series for US children aged 0 to 19 months. To account for disparities, they took note of whether temporal changes in on-time vaccination varied across socioeconomic indicators such as poverty and health insurance status.

Along with the combined 7-vaccine series, which assessed the timeliness of the diphtheria-tetanus acellular pertussis (4 doses), inactivated poliovirus (3 doses), measles-mumps-rubella (1 dose), hepatitis B (HepB; 3 doses), Haemophilus influenzae type b (Hib; 3 or 4 doses, depending on brand), varicella (1 dose), and pneumococcal conjugate (4 doses) vaccinations, investigators assessed the timeliness of the rotavirus and hepatitis A vaccinations. Influenza vaccinations were not assessed, as they are not tied to specific age intervals.

Days undervaccinated described the number of days a child was without recommended vaccination. The metric was measured through age 581 days—equivalent to 19 months—the age at which all combined 7-vaccine series are recommended to be received.

READ MORE: Examining Pharmacists Role in the Current Vaccine Landscape

The study population included 179,154 children with clinician-verified vaccination records in the 2011 to 2021 NIS-Child surveys. Within this population, 74,749 children lived above the poverty level with more than $75,000 in family income; 58,961 children lived above the poverty level with $75,000 or less in family income; and 39,564 children lived below the poverty level. Moreover, 96,284 children had private health insurance only; 61,461 children were covered by Medicaid; 9073 children had another form of health insurance; and 8229 children were uninsured. Any children unaccounted for were either missing poverty status or insurance data.

In general, more children received all combined 7-vaccine series by age 19 months in 2021 (59.4% [95% CI, 57.9%-60.9%]) than they did in 2011 (52.2% [95% CI, 50.8%-53.5%]), representing an improvement. A similar improvement was observed among children who received all vaccinations on time (ie, 0 days undervaccinated), as well; this number increased from 22.5% (95% CI, 21.4%-23.6%) in 2011 to 35.6% (95% CI, 34.2%-37.0%) in 2021 (P < .001).

Strikingly, plots comparing on-time vaccination rates for the combined 7-vaccine series revealed that children from wealthier families improved their vaccination rates faster over time compared to children from families with lower income. Children living above poverty with more than $75,000 in annual family income had a 4.6% (95% CI, 4.0%-5.2%) mean annual increase in on-time vaccination, whereas children from families with lower income had a 2.8% increase (95% CI, 2.0%-3.6%) and children below poverty had a 2.0% increase (95% CI, 1.0%-3.0%).

A similar effect translated to differences in insurance, namely between children with private insurance and children with Medicaid. Children with private health insurance had a 4.6% mean annual increase in on-time vaccination (95% CI, 4.0%-5.1%), whereas children with Medicaid coverage had a 1.6% adjusted mean annual increase in on-time vaccination (95% CI, 0.7%-2.4%).

Investigators noted that their findings indicate that disparities in vaccination timeliness by socioeconomic factors widened over the 11-year period. In light of this, investigators called for better access to and quality of vaccination services for families with lower incomes and those without private insurance.

“Most health system-level and clinic-level initiatives to improve access to immunization services have focused on proximate facilitators, such as contacting parents to let them know their child is coming due for vaccinations, making appointments easy to schedule, and offering walk-in immunization services,” wrote investigators. “Our findings of widening socioeconomic disparities in timely vaccination suggest that such strategies may not have equitable reach across communities and that novel strategies may be needed to facilitate timely immunization services for lower-income children.”

READ MORE: Immunization Resource Center

1. Newcomer SR, Michels SY, Albers AN, et al. Vaccination timeliness among US children aged 0-19 months, National Immunization Survey-Child 2011-2021. JAMA Netw Open. 2024;7(4):e246440. doi:10.1001/jamanetworkopen.2024.6440
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