Between 39 million and 80 million people in the United States contracted influenza A(H1N1) between April 2009 and Dec. 12, 2009, according to data collected by the Centers for Disease Control and Prevention.
The midlevel of the estimated range is 55 million individuals. Of those infected with H1N1 influenza, an estimated 173,000-362,000 here hospitalized, and between 7,880 and 16,460 died, the CDC reported.
Adults 18-64 years of age accounted for another 32 million cases, and about 18 million children 0-17 years of age contracted the virus. There were 5 million cases among individuals 65 years of age and older.
According to two surveys (the National 2009 H1N1 Flu Survey and the Behavioral Risk Factor Surveillance System), an estimated 61 million persons (20% of the U.S. population) had received the monovalent H1N1 vaccine by Jan. 2, 2010, including 29% of children and 22% of health care personnel (MMWR 2010;59:1-5).
About 28% of people in the initial target groups and 38% of those in the limited vaccine subset received at least one dose. The initial target groups included pregnant women, persons who live with or care for infants less than 6 months of age, young adults aged 6 months to 24 years, and persons aged 25-64 years with certain medical conditions. The limited vaccine subset included pregnant women, persons who live with or care for infants less than 6 months of age, health care and emergency services personnel, children aged 6 months to 4 years, and children aged 5-18 years with certain medical conditions.
At an estimated 33%, the vaccination rate was highest among children 6 months to 4 years of age. The lowest rate, 11%, was among adults 65 years of age and older.
“Nearly 90% of adults aged [less than] 65 years with medical conditions that increase their risk for influenza-related complications remain unvaccinated,” wrote J.A. Singleton and colleagues at the CDC.
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