Influenza Vaccine Effectiveness Under 50 Percent This Season: CDC Data

A syringe with an influenza vaccine sits on a table in an Oct. 14, 2020, file image. Mario Tama/Getty Images

Influenza vaccine effectiveness was under 50 percent this season, according to preliminary data from the U.S. Centers for Disease Control and Prevention (CDC), though a smaller study arrived at higher estimates.

Data from the CDC’s New Vaccine Surveillance Network showed the vaccines were 49 percent effective against hospitalization or emergency department visits.