Administration of the quadrivalent influenza vaccine in U.S. children nearly matched that of the trivalent vaccine during the 2013-2014 flu season, Loren Rodgers, Ph.D., and his coauthors from the Center for Disease Control and Prevention’s Immunization Services Division reported in a letter to the editor to Vaccine.

An analysis of 1,976,443 immunization records in patients aged 6 months to 18 years showed that 49.8% of vaccinations administered were trivalent, compared with 46.6% for the quadrivalent type. Another 3.7% of vaccines were an unknown or other type of influenza vaccine .

The report’s findings establish “a baseline for measuring uptake of quadrivalent influenza vaccines,” the authors said. “Trivalent vaccines were administered slightly more frequently, although use of quadrivalent vaccines is expected to increase.”

Read the full report here: ( Vaccine 2015 )