Flu shot less effective this season for some kids, CDC report suggests

This season's influenza vaccines may have been less effective against emergency room visits for some kids compared to last year, a new study by the Centers for Disease Control and Prevention suggests, though effectiveness was still high against hospitalization. 

So far this season, the vaccine's protection against flu hospitalization was at least 63% for children and at least 41% for adults. These estimates of effectiveness against hospitalization, released Thursday in the CDC's Morbidity and Mortality Weekly Report, are considered high for flu vaccines.

But another metric of the shot's effectiveness, looking at protection against infections that result in outpatient visits to places like urgent care clinics or emergency rooms, was worse. Effectiveness was 32% for children and adolescents, from the CDC's U.S. Flu VE network of health care systems. That's down from 67% in last year's estimates.