Facing enormous financial strain because of the shutdown of the theater industry, the health insurance fund that covers thousands of stage actors is making it more difficult for them to qualify for coverage.

Currently, professional actors and stage managers have to work 11 weeks to qualify for six months of coverage. But starting Jan. 1, they will have to work 16 weeks to qualify for a similar level of coverage.

Nonprofit and commercial theater producers contribute to the health fund when they employ unionized actors and stage managers, but because theaters have been closed since March, those contributions — which make up 88 percent of the fund’s revenue — have largely ceased.

“The fact that we have no contributed income is something no one could have foreseen,” said Christopher Brockmeyer, a Broadway League executive who co-chairs the fund’s board of trustees, which is evenly divided between representatives of the Actors’