Influenza vaccines this winter providing moderate levels of protection, CDC data show

Interim estimates from CDC suggest that this year's influenza vaccine is providing about 47% protection against all influenza infections.

Interim estimates from CDC suggest that this year's influenza vaccine is providing about 47% protection against all influenza infections. The protection rate against H1N1 viruses—which are causing most of this year's illnesses around the United States—is 46%, while the protection rate against H3N2 viruses—which are the main viruses in the southeastern part of the country—is 44%. The signs of effectiveness so far this influenza season are "encouraging," according to Alicia Fry, MD, head of epidemiology and prevention in CDC's Influenza Branch. She noted the level of protection provided by the influenza vaccine is within the range of what one would expect during a season in which H1N1 viruses predominate, and it is an improvement over last year, when the mid-season estimate indicated that about 75% of people who had obtained an influenza vaccine were not protected against H3N2 viruses, which were dominant last year. For children aged 17 years and younger, protection against H1N1 was about 62%. For older adults, however, the effectiveness was only about 24% overall and 8% against H1N1 viruses in individuals aged 50 years and older. Fry noted, however, that researchers saw so few infections among older adults that it is too early to determine how well the vaccine was working among these individuals. "We had so few [cases] in the 65 and older [age group] that we couldn't even come up with an estimate," Fry said. New CDC data also indicate that an estimated 9,600–15,900 people died from influenza-associated causes between October 1 and February 2. Up to 15 million people may have been infected and more than 7 million may have sought medical care for influenza, CDC estimates.