(a) An individual hospital or medical expense insurance policy or hospital or medical service plan contract which provides that coverage of a dependent child shall terminate upon attainment of the limiting age for dependent children specified in the policy or contract shall also provide in substance that attainment of the limiting age shall not operate to terminate the coverage of the child while the child is and continues to be both incapable of self-sustaining employment by reason of developmental disability or physical disability as determined by the Department of Behavioral Health and Developmental Disabilities and chiefly dependent upon the policyholder or subscriber for support and maintenance, provided proof of incapacity and dependency is furnished to the insurer, hospital, or medical service plan corporation by the policyholder or subscriber within 31 days of the child's attainment of the limiting age and subsequently as may be required by the insurer or corporation but not more frequently than annually after the two-year period following the child's attainment of the limiting age.

(b) A group hospital or medical expense insurance policy or hospital or medical service plan contract which provides that coverage of a dependent child of an employee or other member of the covered group shall terminate upon attainment of the limiting age for dependent children specified in the policy or contract shall also provide in substance that attainment of such limiting age shall not operate to terminate the coverage of the child while the child is and continues to be both incapable of self-sustaining employment by reason of developmental disability or physical disability as determined by the Department of Behavioral Health and Developmental Disabilities and chiefly dependent upon the employee or member for support and maintenance, provided proof of incapacity and dependency is furnished to the insurer or hospital or medical service plan corporation by the employee or member within 31 days of the child's attainment of the limiting age and subsequently as may be required by the insurer or corporation but not more frequently than annually after the two-year period following the child's attainment of the limiting age.

(c) This Code section shall apply equally to health insurance policies issued pursuant to Chapters 29 and 30 of this title, coverage by health maintenance organizations under Chapter 21 of this title, and health care plans under Chapter 20 of this title.