The Centers for Disease Control and Prevention highly recommends the flu vaccine for certain high-risk groups including people with chronic illnesses, children between the ages of six and 23 months, and people aged 65 and over. A national poll conducted by the Harvard School of Public Health Project on the Public and Biological Security found in December 2003 that nearly half (47%) of people with chronic illnesses had not had a flu vaccination in the past three months. In addition, more than three-fourths (78%) of parents reported that their children ages six to 23 months had not received a flu vaccine. This was the case even though the vaccine recommendation for these young children was widely known by Americans (74%). One in 10 Americans (10%) reported that they had not gotten a flu vaccine due at least in part to shortages. About one-third of these people (3% of the public) still planned to get vaccinated in the next three months, but two-thirds (7%) do not. The study was designed and analyzed by researchers at the Harvard School of Public Health.