We think flu shots work great globally, but that's an illusion—almost all the data comes from wealthy countries.
Standard estimates suggest the flu shot is about 46% effective, but this study reveals those numbers come from regions like North America and Europe. When the model accounts for the missing data from low-income countries, the estimated effectiveness varies wildly from 61% down to just 13%, suggesting the vaccine may be performing far worse in the developing world than we realized.
Imbalanced Evidence Shapes Global Estimates of Influenza Vaccine Effectiveness
SSRN · 6426381
Background: Estimates of influenza vaccine effectiveness (VE) are widely used to inform vaccination policy. However, the evidence underlying these estimates is imbalanced across countries. Most VE studies are conducted in high-income settings, whereas many low- and middle-income countries lack surveillance systems capable of generating VE estimates. We examined how geographic imbalance in the global evidence base may influence assessments of influenza vaccine effectiveness.<br><br>Methods: We co