Huge swaths of the United States, especially rural and inner-city areas, have no primary-care physicians. The Department of Health and Human Services estimates that the shortage is at least 16,000 doctors.Missouri has passed a new law to deal with the problem, but it is exceedingly controversial.The law will allow medical school graduates to work as “assistant physicians” treating patients in under-served rural areas, even without being trained in a residency program. In the U.S., at least one year of residency after medical school is usually required to practice medicine independently. Most medical school graduates spend at least three years in residency before starting to practice on their own.Under Missouri’s new law, an assistant physician must have passed the first two sections of the national licensing exam for doctors but not the final one. If they want to become full-fledged physicians, they will still have to pass the last test and do a one-year residency.Assistant physicians — not to be confused with physicians’ assistants, who are not medical school graduates — must work in person with a collaborating physician for 30 days and could prescribe most medications. They then may treat patients on their own if they practice within 50 miles of that supervising doctor. They also must be approved by the state Board of Healing Arts, which issues medical licenses.The Missouri State Medical Association, which represents the state’s 6,500 physicians, helped draft the legislation in response to a severe shortage of healthcare professionals. At least one-fifth of Missouri’s population lacks adequate access to a doctor.Critics, including many national medical groups oppose the idea, argue that letting someone practice without a residency dangerously weakens professional competency.Who will these new doctors be? Some will be graduates of medical schools who failed to get into a residency program — a growing problem as more medical schools open but more residencies do not. Even some highly competitive students do not get a residency in their chosen specialty. This year, among students who are more than one year out of medical school, and thus probably in their second try at getting a residency, only 48 percent succeeded.A few medical school grads will choose to be an assistant physician rather than enter residency. Still, assistant physicians are not likely to be the cream of the U.S. medical school crop. But that crop is not yielding many primary-care providers, and new residency slots are not going to open any time soon.Can someone who successfully got through four years of medical school, including a lot of clinical time, who is supervised by another doctor for a month and certified by the state board, deliver high-quality primary care to people who currently have nothing?I think it is very likely that most can. Fairly good primary care is a lot better than no care at all. Arthur L. Caplan is the director of medical ethics at NYU Langone Medical Center in New York.