( CNN ) -- The flu is hitting younger people harder this season than in years past , the Centers for Disease Control and Prevention reported Thursday . People between the ages of 18 and 64 represent 61 % of all influenza-related hospitalizations recorded during the current flu season -- a significant increase compared with previous years when this age group represented about 35 % of cases . More flu deaths than usual have also occurred in people under 65 . Adults between 25 and 64 account for more than half of flu deaths this season , according to the CDC , compared with less than a quarter last year . `` Influenza can make anyone very sick , very fast and it can kill , '' said the CDC 's director , Dr. Tom Frieden . `` Vaccination every season is the single most important thing you can do to protect yourself . '' CDC experts estimate only a third of people 18 to 64 had been vaccinated by November . About 40 % to 45 % of Americans get vaccinated each year , Frieden said . Health officials continue to encourage vaccinations for everyone who is at least 6 months old . The CDC 's Morbidity and Mortality Weekly Report noted this year 's flu vaccine reduces the chance of having to go to the doctor for treatment by about 60 % across all age groups . In past years , the vaccine 's effectiveness has ranged from 30 % to 65 % . The CDC has known for weeks that the dominant flu strain this season is the H1N1 virus , which first emerged in April 2009 and caused a pandemic . It 's included in all flu shots and nasal vaccines this year , according to the MMWR . `` We are committed to the development of better flu vaccines , but existing flu vaccines are the best preventive tool available now , '' Frieden said . Pregnant women are at particularly high risk of developing serious complications from the flu , such as pneumonia . Leslie Creekmore of Arkansas was 20 weeks ' pregnant when she contracted the flu this month . Five days after checking into a hospital , she miscarried . Three weeks later , Creekmore died . She did not get the flu vaccine . Fifty pediatric flu-related deaths have been reported during the current flu season , according to the MMWR . Adult flu deaths are not reported on a national basis , but the CDC estimates that between 3,000 and 49,000 people die each year because of the flu and flu-related illness . When H1N1 first surfaced , California health officials decided to make reporting fatal influenza cases in all individuals under 65 mandatory . As of February 14 , local health officials had reported 243 deaths . `` The 405 reports of severe cases ( i.e. , fatal and ICU cases combined ) were more than in any season since the 2009 pandemic , '' officials wrote in the MMWR . Influenza activity in the United States remained elevated through February 8 , according to the CDC . Twenty-four states reported widespread flu activity that week . `` Widespread '' means that more than 50 % of geographic regions in a state -- counties , for example -- are reporting flu activity . The designation addresses the spread of the flu , not its severity . Experts expect elevated flu activity in parts of the United States for several more weeks , especially in states where flu activity started later . `` I want to remind you that the season is not over , '' said Dr. Anne Schuchat , director of the National Center for Immunization and Respiratory Diseases . `` There is still a lot of influenza circulating . If you have n't been vaccinated yet , it 's not too late for you to benefit . '' In addition to getting the vaccine , washing your hands frequently and staying home when you 're sick can help you and others get through the flu season . Doctors recommend using antivirals within the first two days of experiencing any flu-like symptoms . CNN 's Jacque Wilson , Miriam Falco and Ashley Hayes contributed to this report .
People year represent 60 % of all flu-related hospitalizations , influenza says . Health officials continue to recommend flu vaccines , including for pregnant women . This between 18 and 64 's flu vaccine reduces chances of having to see a doctor by 61 % , report says .