Generating Background Rates of Adverse Events for Vaccine Safety Evaluation

Background rates refer to how often a health condition or medical event occurs naturally in a population over time, before any new intervention like a vaccine is introduced.

In vaccine safety research, an Adverse Event is any unwanted health outcome after vaccination. This can range from mild symptoms (such as a sore arm or mild fever) to more serious conditions (like allergic reactions or heart issues). An Adverse Event of Special Interest (AESI) is a specific health outcome monitored closely because it could be linked to a vaccine or has been associated with vaccines in the past. Importantly, just because an adverse event happens after vaccination does not mean the vaccine caused it.

Background rates for Adverse Events of Special Interest (AESI) provide a baseline: they show how often these events happen before a vaccine is introduced. Comparing these rates to what happens after vaccination helps experts spot changes that may need further investigation to determine if there’s a causal link or another explanation. Background rates are essential for interpreting vaccine safety.

Clinical trials may not capture rare or long-term adverse events, so ongoing monitoring after vaccines are introduced (known as post-licensure surveillance) is crucial. Without background rates, it’s difficult to know if health events seen after vaccination are simply coincidental or possibly related to the vaccine. BRAVE provides these real-world benchmarks.

BRAVE generates this real-world evidence - background rates of Adverse Events of Special Interest - by collecting data from national health systems, hospital databases and community population surveys across five African countries.