How effective this year's flu vaccine could be

To determine the vaccine's effectiveness, researchers looked at 2,780 hospitalizations associated with severe acute respiratory infections between March 27 and July 9 in Chile, Brazil, Uruguay, Paraguay, and Argentina.

Vaccine effectiveness evaluation began two weeks after the start of each country's vaccination campaigns, and researchers looked at three specific groups — young children, older adults, and people with preexisting medical conditions.

Just over 90% of the 900 positive specimens were influenza A while just over 9% were influenza B. Roughly 99% of the influenza A specimens were subtyped as A(H1N1)pdm09.

The researchers found the vaccine had an overall effectiveness of 51.9% against flu-related hospitalization. That effectiveness rose to 55.2% when specifically looking at the predominant influenza strain, A(H1N1)pdm09.

Among children ages six and younger, the vaccine was around 70% effective. Meanwhile, among adults ages 60 and older, the vaccine was 38% effective against hospitalizations.

"These early, interim estimates, provided before the expected end of seasonal influenza virus circulation, suggest that vaccination substantially reduced the risk for severe influenza illnesses, underscoring the benefits of influenza vaccination," the researchers wrote.

"Health authorities worldwide should encourage influenza vaccination for persons at increased risk for severe disease, including young children, persons with preexisting health conditions, and older adults, as well as those at increased risk for exposure to or transmission of influenza virus, such as health care personnel," they added. (Ingram, MedPage Today, 9/8; Ducharme, TIME, 9/8)

Writing for USA Today, Michael Daignault, an ED doctor in Los Angeles, debunks three common myths many believe about the flu.