MILLIONS of women and children coming off welfare aren't supposed to lose their health insurance, at least not right away. By law, they retain their Medicaid eligibility for a while, the children until they reach age 19 so long as they remain poor. But the system turns out not to be as seamless as it sounds. A lot of welfare leavers are vanishing from the Medicaid rolls as well; they become uninsured.

Data are now available on families that left welfare in the period 1995-97. By the time the families had been off the rolls a year, between a fourth and a third of the children and nearly half their mothers were without insurance, a new study has found. The data for the last two years are not as good, but the problem is known to persist. If the percentages in 1998-99 were about the same as earlier, more than a million children and about as many parents can be said to have lost health insurance.

The welfare debate has shifted. In every state, the caseload is sharply down. Many former recipients are working, mostly at low wages. The work is an obvious plus, but the families continue to need help. Some may actually need more help to stay off the rolls than they did when they were on. Part of the help has to be health insurance, otherwise unaffordable. Critics--we are among them--believe that welfare reform has produced a weakening of the safety net. Defenders, including the governors who operate Medicaid, would seem to us to have a vested interest in proving that's not significantly so. At a minimum, that means finding and restoring the health insurance of the eligible children that have been let go.