Prior studies have found that up to 14 percent of children as of 2000 were underinsured, and based on that number, Lee's group estimates that up to 1.2 million may not be receiving all of the recommended vaccines.
Lee says boosting coverage would likely require persuading private health insurance plans to pay for preventive care as well as beefing up the public safety net.
Most of the new vaccines are for disease such as rotavirus that are hobbling but not major killers in the U.S. Still, people may increasingly come to expect them in much the way they came to expect the measles vaccine in the 1970s and 1980s, Orenstein says. Put it this way, he notes: "I would want my children vaccinated against them."