ATLANTA — THE alarming number of measles cases — a record 644 last year, and 102 last month, the most since the disease was declared eliminated in the United States in 2000 — has focused scrutiny on parents who refuse vaccinations for their children. There are some who want state and local governments to sue, or even criminally charge, such parents. A bill in California would end all nonmedical exemptions to immunization requirements.

For epidemiologists like me, eliminating exemptions may seem satisfying, but it is not the wisest policy for protecting kids. Instead, we should borrow a concept from behavioral economics, and use administrative rules and procedures to “nudge” parents to immunize their kids, rather than trying to castigate or penalize these parents.

Currently, all states allow medical exemptions, since some children — for example, those getting chemotherapy or who have certain types of immune disorders — cannot safely receive vaccines. All but two states (Mississippi and West Virginia) allow exemptions for religious reasons. Nineteen states allow exemptions based on personal (or “philosophical”) beliefs. Such beliefs are increasingly cited by parents whose misplaced skepticism is not really principled but premised, rather, on false notions like that of a link between autism and the measles vaccine.

So shouldn’t all states follow the example of Mississippi and West Virginia, and ban all nonmedical exemptions? The courts have generally upheld such bans, but the political backlash is great, as history shows. After the smallpox vaccine was made compulsory in England and Wales in 1853, there were years of protests, until a commission exempted those with conscientious objections.