Introduction
Anaphylaxis is defined as a potentially fatal, severe and systemic allergic reaction that occurs suddenly after contact with an allergy-causing substance 1. Although rare, deaths caused by food-induced anaphylaxis are continuing to occur at an estimated rate of 5 to 200 cases per year in the United States2. Anaphylaxis registries and prospective studies from the West have reported an increasing trend of anaphylaxis incidence over time 3-5. In contrast, the burden of anaphylaxis was thought to be lower in Asia and different from the West in terms of varying age distribution, anaphylaxis triggers and low usage of adrenaline auto-injectors (AAI) as first-line treatment6,7. However, a more recent study suggested that children of Asian ethnicity born in Australia may conversely be at higher risk of anaphylaxis compared to other ethnicities8. This discrepancy highlights the need for more accurate estimates of the true anaphylaxis burden in Asian countries. Time-trend analyses of anaphylaxis incidence across longer time periods, using a unifying methodology on a territory-wide population, have never previously been reported.
In this study, we took an advantage of a comprehensive electronic records system to determine the incidence rates of anaphylaxis between 2009 and 2019 in Hong Kong and investigated the longitudinal trends of AAI prescriptions.