Characteristics of hospitalized adult cases in vaccine clinical trial in period of the COVID-19 pandemic

Abstract

A retrospective analysis to describe the hospitalized characteristics was conducted on all 461 reports of hospitalized cases, unrelated to vaccine, in a COVID-19 vaccine clinical trial among adults from September 2021 to January 2023. Hospitalizations due to COVID-19 accounted for the highest proportion, with 192 cases (41.4%). Other major causes included gastrointestinal diseases (20.4%), circulatory diseases (15.9%), infections and parasitic diseases (12%), injuries/poisoning (10.4%), and respiratory diseases (10.0%). The changing hospitalizations related to COVID-19 reflect the impact of the pandemic. Most hospitalizations were due to infectious diseases with acute progression, predominantly occurring during seasonal transitions. Additionally, 15% of hospitalizations occurred at out-of-province healthcare facilities or private hospitals. The proactive surveillance system proved effective, as the majority of hospitalizations were detected by the research team (call center staff, 24/7 physicians, participant managers, and the study team during visits), with self-reported hospitalizations accounting for only 13%. Clinical trials should integrate multiple detection channels and increase the frequency of reminders.