CDC - Influenza (Flu) | Flu Vaccine Effectiveness: Q & A for Health Professionals
How is influenza vaccine effectiveness measured?
Vaccine efficacy and effectiveness studies use various endpoints or outcomes, which influence how we interpret the results. These endpoints may include the prevention of medically attended acute respiratory illness (MAARI), prevention of laboratory-confirmed influenza virus illness or hospitalization, prevention of influenza-like illness (ILI, such as illness with fever and cough or sore throat), or influenza-associated hospitalizations or deaths. Studies that use outcomes such as an influenza laboratory-confirmed outcome provide the most specific estimates of the impact of the vaccine in preventing influenza. The more non-specific the outcome being measured (e.g., all pneumonia hospitalizations or influenza-like illness that include many illnesses not caused by the influenza virus), the lower the estimates of vaccine effectiveness. For example, a study by Bridges et al. (JAMA 2000) among healthy adults found that the inactivated influenza was 86% effective against laboratory-confirmed influenza, but only 10% effectiveness against all respiratory illnesses in the same population and year.
Posted by gruwell at January 24, 2007 4:02 PM | TrackBack