Only a third of all people over age 18 got a flu shot last year, for example, despite the CDC’s recommendation that everyone over 6 months of age receive it. Immunization levels were even lower for many other vaccines. All adults who are age 60 or older should get the shingles vaccine, but just 10 percent of that group had received it, according to the CDC. Likewise, only 17 percent of women ages 19 to 26 had gotten even one of the three doses of the human papillomavirus vaccine, which protects against cervical cancer.

With its emphasis on prevention, the health-care overhaul law aims to improve vaccination rates by expanding coverage requirements. “It’s a total game-changer in terms of adult coverage of immunizations,” says Sara Rosenbaum, who chairs the department of health policy at George Washington University’s School of Public Health and Health Services. The new law, however, leaves some gaping holes, experts caution.