(368) Vaccine Cohort Event Monitoring: Enhancement of Safety Data Collection

Background: Cohort event monitoring (CEM) is one study design that can be considered to assess vaccine post-authorisation safety. CEM typically makes use of an app to collect adverse events (AEs) from subjects during the prospective follow-up period. This design, used to assess the safety of Covid-19 vaccines in Western countries during the pandemic, may present limitations when applied to other indication and population settings.

Objectives: To review approaches to address CEM limitations and improve safety data collection.

Methods: We reviewed the 3 CEM studies that we worked on over the past 2 years and summarized solutions to enhance safety data collection.

Results: Compliance is key to the subject-centric safety data collection methodology especially in the case of long follow-up periods and a non-pandemic context. Several solutions can be implemented to promote subject compliance, included but not limited to: pre-defined schedules for data collection; regular reminders/notifications sent to subjects; multiple contact options (e.g. app plus telephone reminders), possibility of the subject to report AEs in real-time; escalation process with contacts to physician or next of kin to minimise loss to follow-ups.
In a pure app-based CEM, AE collection relies entirely on subject self-reporting. Although acceptable in a pandemic situation with vaccines for which mostly mild AEs were anticipated, further validation of reported AEs may be warranted in a non-pandemic context and in the case of other vaccines with potentially serious AE following immunization. Taking the example of dengue vaccines, the need to identify severe dengue episodes requires a clinical confirmation. In light of this, we planned for additional processes involving medical confirmation of the subject-reported AEs. This required notifying the recruiting/treating physician of the reported AE and requesting they confirm the AE and collect relevant medical information in a safety event form.
The use of an app implies that subjects have access to a smartphone, tablet or computer and to a reliable internet connection. This may be a limitation in some low- and middle-income countries, or in some socio-economic groups in high-income countries. Where relevant, optimising participation by offering other data collection options such as Computer Assisted Telephone Interviews enabled us to limit selection bias and promote diversity, and to use these study designs in a larger range of geographies.

Conclusions: In the wake of Covid-19 vaccine safety studies, new use cases have emerged to apply modified CEM designs in various vaccine types and geographies, by introducing methods enhancing the approach for a better validation of safety data and a wider applicability.