Effectiveness of email-based reminders to increase vaccine uptake: a systematic review

In times of vaccine hesitancy and decreasing immunization coverage, it is crucial to exploit the potential of digital solutions to support immunization programmes and ultimately increase vaccine uptake. Scant evidence exists on the impact of email-based immunization reminders. In particular, while email communication is exponentially increasing at the global level, its use for health communication is still sporadic and limited data exists on its application to immunization programmes. The objective of this study is to systematically retrieve and critically appraise the available literature on the effectiveness of email-based reminders to increase vaccine uptake, with the ultimate aim to inform and encourage its integration in the implementation of immunization programmes.

We conducted a systematic review of literature following the PRISMA. We included studies providing quantitative comparative data on any measure of vaccine uptake. We extracted data on study design, study population, vaccine type and details of email-based interventions; data were pooled by type of comparison (no reminders, traditional reminders, other digital reminders).

Eleven studies were included, 90% with experimental study designs. While email communication succeeds in increasing vaccine uptake when compared with no intervention, weak and heterogeneous data exist supporting the superiority of email reminders, as compared to traditional methods or other digital reminders. Encouraging evidence report the effectiveness of reminder methods combining different strategies and tailored to target populations' preferences.

Theoretically, email communication offers many advantages: it is cheaper and faster, it can be automated and linked to electronic immunization registries, and reach people on the move. As we urge the need for further research to prove email communication impact on vaccine uptake in different settings, we underline the importance of identifying how to best integrate email communication in vaccine delivery equipping immunization programmes with technical infrastructures and normative frameworks suitable to embrace innovation.