This season's flu vaccine has reduced the risk for influenza-associated medical visits by 61% across all age groups, and it's not too late to get a flu shot for protection the rest of the season, the federal Centers for Disease Control and Prevention announced Thursday.
Because flu viruses change from season to season, the CDC conducts studies each year to determine how well the vaccine works against specific viruses that are circulating.
Last season, the flu vaccine was minimally effective for the elderly. But this season's vaccine is effective for the elderly and all other age groups, including young and middle-aged adults, who have been hit hardest, the CDC reported.
Adults and children ages 6 months and older who have not yet received the 2013-'14 influenza vaccine should still be vaccinated, according to the CDC, as elevated influenza activity likely will continue for several more weeks. The CDC recommends yearly flu vaccinations.
The mid-season report presented data on 2,319 children and adults enrolled in the U.S. Flu Vaccine Effectiveness Network from Dec. 2 through Jan. 23, including more than 900 who sought medical treatment at the Marshfield Clinic — one of five CDC-funded sites that are part of the data collection network.
Of the patients who came to the Marshfield Clinic with a cough and agreed to be swabbed for influenza, 314 (36%) tested positive. Researchers then compared those who got flu shots against those who had the flu and those who didn't have it, said Edward Belongia, an epidemiologist at the Marshfield Clinic Research Foundation.
The national study found the vaccination offered substantial protection against the predominant flu virus circulating this season, pH1N1 — the same virus that emerged in 2009 and spread in a worldwide pandemic.
Influenza deaths this season are following a pattern similar to the 2009 pandemic. People ages 25 to 64 have accounted for about 60% of flu deaths, compared with 18%, 30%, and 47% for the three previous seasons, respectively, according to the CDC.
During the 2009-'10 pandemic, those ages 25 to 64 accounted for an estimated 63% of flu deaths, and those ages 18 to 64 accounted for about 56% of hospitalizations.
Nearly the same percentage of flu hospitalizations so far this season — approximately 61% — occurred among people ages 18 to 64 years, the CDC reported.
Last season, when influenza A (H3N2) viruses were the predominant circulating viruses, those ages 18 to 64 accounted for only 35% of hospitalizations.
Surveillance data provide a reminder that while some age groups are at increased risk of influenza complications every year, influenza can cause severe illness in people of any age, even in adults 18 to 64 years.
When people do get the flu, antiviral treatment can reduce severe outcomes, especially when administered early.