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ANN ARBOR – Inequities in vaccination are a major contributor to disparities in childhood health and survival.

Completion of childhood vaccination schedules—ensuring a child receives all recommended vaccines that prevent infectious disease—is important in reducing death rates among children.

But vaccination timeliness—ensuring the recommended vaccines are administered at the recommended time—is also of utmost importance.

This is evidenced in sub-Saharan Africa, where some of the highest global rates of childhood death coincide with very low vaccination (or immunization) schedule completion—less than one third of countries in sub-Saharan Africa report immunization schedule completion in infants.

The low rates of age-appropriate vaccination directly threaten the progress made in the control and elimination of vaccine-preventable diseases. Increasing vaccination rates would directly contribute to improving childhood survival.

As part of a research team led by Cara Bess Janusz, we recently assessed vaccination timing and series completion for more than 70,000 children aged 12–35 months living in 33 countries across sub-Saharan Africa who were included in the immunization module of the Demographic and Health Surveys (DHS) conducted between 2010 and 2019.

Among children with complete immunization records, the percent of children vaccinated with delays of one month or more was high. Late vaccination was more common for children born to mothers with lower levels of educational attainment and wealth. And perhaps most importantly, vaccination delays for any recommended dose were significantly connected with not completing the recommended immunization schedule within 12 months compared with children who received on-time vaccination.

Patterns of repeated delays for individual immunizations across the childhood schedule resulted in significantly higher chances of drop off from the recommended series than receiving on-time vaccination.

Assessment of vaccination timeliness is essential to identifying age-specific risks of vaccine-preventable diseases, which continue to contribute at high rates to under-5 deaths in sub-Saharan Africa. Although the uptake of individual vaccine doses has improved, generalized measures of vaccine coverage are an imprecise predictor of the population risk. Such measures do not account for the timing of vaccination and the resulting age-specific protection—or the lack thereof—when delays lead to additional delays or eventual dropout and undervaccination.

Our study suggests that dose-specific delays are common and that those delays lead to a significantly higher probability of dropping off the schedule, resulting in prolonged susceptibility to specific vaccine-preventable diseases beyond the first year of life and potential increases of the spread of those diseases across the community.

Timely initiation of vaccination should contribute to higher rates of immunization schedule completion, improving the reach and impact of vaccination programs on child health outcomes in sub-Saharan Africa.

About the Authors
Margaret Frye is an associate professor of Sociology in the College of Literature, Science, and the Arts. Her research investigates the complex and often misaligned relationships between culture, ideas, and demographic patterns using a diverse set of qualitative and quantitative methods. Frye’s research is located primarily in sub-Saharan Africa, including a current longitudinal data collection project in Kampala, Uganda, examining shifting understandings of social status.

Abram Wagner is a research assistant professor of Epidemiology in the School of Public Health. He studies predictors of vaccine-preventable disease incidence, with a particular focus on vaccine hesitancy. Wagner’s research is targeted toward evidence-based programs and policies that work toward the control of a broad range of vaccine-preventable diseases.

The original article was published by the Center for Global Health Equity at the University of Michigan.