So far, the 2013-2014 influenza season has been hardest on young and middle-age adults, with 61% of flu hospitalizations occurring in the 18- to 64-year-old age group, the Centers for Disease Control and Prevention reported in this week’s Morbidity and Mortality Weekly Report. This is a drastic jump from the previous season, when this age group accounted for only 35% of hospitalizations.
The report also found that the young adult population has accounted for an increased number of influenza-related deaths than in previous years, with adults aged 25-64 years of age accounting for 60% of flu deaths this season, compared with just 18%, 30%, and 47% for the previous three seasons, respectively (MMWR 2014; 63;137-42).
"Influenza can make anyone really sick, really fast, and it can kill," Dr. Thomas R. Frieden, director of the Centers for Disease Control and Prevention, said in a teleconference. "Vaccination is the single most important thing you can do to protect yourself."
The CDC conducted an interim analysis of flu vaccine effectiveness in 2,319 children and adults enrolled in the U.S. Influenza Vaccine Effectiveness (Flu VE) Network from Dec. 2, 2013 to Jan. 23, 2014. Early estimates from the report found that vaccination reduced the risk of illness by about 60% across all age groups.
Younger and middle-age adults are the least likely to be vaccinated, according to the report. Early estimates indicate that as of mid-November, just 34% of 18-64 year-olds had received this season’s influenza vaccine, compared with 41% of children aged 6 months to 17 years and 62% of adults aged 65 years or older.
Though vaccination should be the first line of defense, Dr. Frieden emphasized the importance of treating patients who present with flulike symptoms with antiviral medication immediately, rather than waiting on test results. This is especially important in patients with underlying medical conditions such as lung disease, asthma, diabetes, or obesity that increase their risk for complications, he said.
The most prevalent flu strain in the 2013-2014 season has been H1N1, which emerged as a pandemic in the United States in 2009. H1N1 has continued to circulate since the 2009-2010 season, but this is the first time it has returned as the dominant strain.
Because the predominant influenza strain can vary from season to season, CDC recommends annual flu shots for everyone aged 6 months or older, said Dr. Anne Schuchat, assistant surgeon general for the United States Public Health Service and director of the National Center for Immunization and Respiratory Diseases.
Dr. Schuchat said she hoped the greater access of the vaccine outside of medical offices would encourage more young adults to get the vaccine.
"Vaccinations are not just a doctor thing," she said. "They’re now available at workplaces, pharmacies, and grocery stores, which make it easier to get vaccinated."
She also added that the current flu season has not yet ended and could extend as far as May. "The season is not over," she said. "If you haven’t been vaccinated yet, it’s not too late to benefit."
Final results for flu vaccine effectiveness are expected to be released later this year.