Changes in on-time vaccination following the introduction of an electronic immunization registry, Tanzania 2016-2018: interrupted time-series analysis

Abstract

Background: Digital health interventions (DHI) have the potential to improve the management and utilization of health information to optimize health care worker performance and provision of care. Despite the proliferation of DHI projects in low-and middle-income countries, few have been evaluated in an effort to understand their impact on health systems and health-related outcomes. Although more evidence is needed on their impact and effectiveness, the use of DHIs among immunization programs has become more widespread and shows promise for improving vaccination uptake and adherence to immunization schedules.

Methods: Our aim was to assess the impact of an electronic immunization registry (EIR) using an interrupted time-series analysis to analyze the effect on proportion of on-time vaccinations following introduction of an EIR in Tanzania. We hypothesized that the introduction of the EIR would lead to statistically significant changes in vaccination timeliness at 3, 6, and > 6 months post-introduction.

Results: For our primary analysis, we observed a decrease in the proportion of on-time vaccinations following EIR introduction. In contrast, our sensitivity analysis estimated improvements in timeliness among those children with complete vaccination records. However, we must emphasize caution interpreting these findings as they are likely affected by implementation challenges.

Conclusions: This study highlights the complexities of using digitized individual-level routine health information system data for evaluation and research purposes. EIRs have the potential to improve vaccination timeliness, but analyses using EIR data can be complicated by data quality issues and inconsistent data entry leading to difficulties interpreting findings.

Keywords: Digital health intervention; Electronic immunisation registry; Interrupted time-series analysis; Routine health information system; Vaccination timeliness.

Fig. 1

Timeline of EIR Introduction. Note: TImR: Tanzania Immunization Registry

Fig. 2

Casual linkage diagram of the relationships and assumptions between implementation of an electronic immunization registry and improved vaccination timeliness

Fig. 3

Number of children with a documented vaccination and proportion vaccinated on-time by vaccine type and region, Tanzania, November 2016-July 2018* *Red line indicates when the EIR was introduced (approximately); blue line indicates when the SMS reminders were introduced

Fig. 4

Incomplete or missing vaccination records among all children registered in the EIR* *For the selected vaccines of interest and includes doses administered after data pull and doses administered before a date-of-birth, which were removed for the analysis

Fig. 5

Regression results for primary model* *Red dotted line indicates EIR-introduction date; black dots indicate the average proportion of vaccinations per facility per month with the black lines indicating their associated 95% confidence intervals; blue lines indicate the change in slope for the proportion of children vaccinated on-time per month per facility

Fig. 6

Regression results for sensitivity analysis* *Red dotted line indicates EIR-introduction date; black dots indicate the average proportion of vaccinations per facility per month with the black lines indicating their associated 95% confidence intervals; blue lines indicate the change in slope for the proportion of children vaccinated on-time per month per facility