The 'test-negative' design is a key methodology for estimating how well influenza and COVID-19 vaccines work. It compares vaccinated individuals who test positive for the virus to those who test negative.
This approach has been utilized in various studies, including those led by the CDC, to provide insights into vaccine performance during outbreaks.
While the 'test-negative' design offers valuable data, it is important to recognize its limitations and the need for careful interpretation of results.