Lessons Learned on Observed-to-Expected Analysis Using Spontaneous Reports During Mass Vaccination

Area of Science:

• Pharmacovigilance
• Vaccine Safety
• Regulatory Science

Background:

• The COVID-19 vaccination campaign necessitated robust real-time safety monitoring.
• Spontaneous reporting systems are crucial for detecting potential vaccine safety concerns.

Purpose of the Study:

• To evaluate the utility of observed-to-expected (O/E) analysis for COVID-19 vaccine safety surveillance.
• To identify key considerations for the design and interpretation of O/E analyses in pharmacovigilance.

Main Methods:

• Observed-to-expected (O/E) analysis was employed, comparing reported adverse events post-vaccination to expected event rates in unvaccinated populations.
• Methodology relies on established regulatory guidelines and scientific literature.

Main Results:

• O/E analysis provided valuable real-time evidence on emerging safety concerns for COVID-19 vaccines.
• The study highlighted critical factors influencing the reliability of O/E analyses.

Conclusions:

• Harmonized and stratified data collection for vaccine exposure and spontaneous reports is essential.
• Accurate background incidence rates for adverse events of special interest are crucial for interpretable O/E analyses.
• Lessons learned from COVID-19 vaccine safety monitoring are generalizable to future pharmacovigilance efforts.