CDC: Flu vaccine more effective this year

This season's flu vaccine has reduced the risk of influenza-associated medical visits by 61% across all age groups, according to the Centers for Disease Control and Prevention (CDC). Thus far it appears to be outperforming its predecessor from 2012 to 2013, which had an effectiveness rate of 51%.

In some years, that rate has dipped below 40%.

But of particular note, the vaccine has proven to provide substantial protection (62%) against pH1N1 influenza virus, which has been the predominant influenza virus this season. This is the virus that emerged in 2009 and caused a pandemic, and has continued to circulate in the United States. It has been included as the H1N1 component of all seasonal influenza vaccines since that time.

The effectiveness data is reported the agency's February 21 issue of Morbidity and Mortality Weekly Report (MMWR), and is based on study results of 2,319 children and adults with acute respiratory illness who were enrolled in the United States Influenza Vaccine Effectiveness Network December 2, 2013 to January 23, 2014.

Hospitalization rates for influenza-related symptoms have been the highest among children under the age of 5 years, and among those between the ages 50 to 64 years and people aged 65 years and older. Overall, people aged 18 to 64 years have accounted for about 60% of reported influenza-related hospitalizations, and 22% of cases the among women of childbearing age (aged 15 to 44 years) occurred in those who were pregnant.  

However, vaccination rates are less than optimal. To date, only about a third of adults (34%) aged 18 to 64 years have been vaccinated, and 41% of children and adolescents. The highest vaccine rates (62%) have been observed in adults aged 65 years and older.

The CDC cautions that the flu season is far from over, and influenza activity is still elevated and widespread across most of the country. These effectiveness rates are also only interim estimates, and statistics for the full influenza season will be published later this year.