Blue Shield of California is shutting down for the four days after Labor Day to reduce its payroll-related liabilities, citing losses in California’s Covered California Obamacare exchange and other commercial and individual lines of business.

The move will affect most of its 6,000 employees in California, except about 1,000 who work for Care1st, which it acquired last fall for $1.2 billion, and some staffers in customer service and related areas who will remain on the job. The exact number of workers involved hasn’t yet been tabulated, according to the San Francisco-based insurer.

. . .