"This is a challenging flu season for millions of Americans and their families, and it's not over yet," Health and Human Services Secretary Kathleen Sebelius said in a release Friday.
Sebelius urged people to obtain vaccinations during this week's National Influenza Vaccination Week, in which more than 130 events across the nation were to highlight the need for increased flu protection.
From April through mid-November, H1N1 flu infected an estimated 47 million U.S. residents and caused nearly 10,000 deaths, said Thomas Frieden, director of the Centers for Disease Control.
"We do not know how many more cases of flu there will be in the coming weeks and months, but we do know that the H1N1 vaccine is the best way to protect yourself," Frieden said in the Health and Human Services release.
CDC: Get your flu vaccine