Another major health insurer has signed on to the effort to protect graduating college students from a possible gap in access to health coverage.

CIGNA Corp., Philadelphia (NYSE:CI), has agreed to make sure that the children of group insurance plan enrollees can stay on their parents’ coverage up until age 26 starting June 1.

Employers that provide self-funded plans administered by CIGNA also can offer early-access to young adult coverage continuation, the company says.

Most other national health carriers also have announced plans to offer early access to young adult coverage continuation.

Those carriers include Aetna Inc., Hartford (NYSE:AET); WellPoint, Indianapolis (NYSE:WLP) and other members of the Blue Cross and Blue Shield Association, Chicago; Humana Inc., Louisville, Ky. (NYSE:HUM); Kaiser Permanente, Oakland, Calif.; and UnitedHealth Group Inc., Minnetonka, Minn. (NYSE:UNH)

The new Patient Protection and Affordable Care Act will require plans to let young adults stay on parents’ coverage up until age 26, but that provision will not take effect until Sept. 23.

U.S. Health and Human Services Secretary Kathleen Sebelius wrote to carriers last week to ask them eliminate the access gap.

Some carriers said they already had been letting holders of individual policies keep adult children on their coverage up until age 26. At those carriers, the recently announced changes mainly affect the adult children of partipants in insured group plans