Some pregnant women who have been infected with the 2009 H1N1 virus have had severe illness. Overall, pregnant women have had higher rates of hospitalization than the general population. About 6% of confirmed H1N1 2009 influenza deaths in the US have been in pregnant women, while only about 1% of the general population is pregnant at any given time. One recent large case control study found that the seasonal flu shot (inactivated flu vaccine) given to pregnant women reduced flu illness in their infants under 6 months of age by 63%*. This study confirms that seasonal flu vaccination of pregnant women can benefit both mothers and infants. The Advisory Committee on Immunization Practices (ACIP) designated pregnant women as one of the initial target groups to receive the 2009 H1N1 vaccine as soon as it is available. Clinical trials evaluating the vaccine in pregnant women are underway by the National Institute of Allergy and Infectious Diseases (NIAID).