Workers at Kaiser Permanente have voted to remain members of the Service Employees International Union rather than switch to the upstart National Union of Healthcare Workers.

SEIU-United Healthcare Workers West received 58.4 percent of the votes, compared to 40.6 percent for the NUHW, while 1 percent voted to have no union in a mail-in election conducted April 5-29.

The ballots were counted on Thursday by the National Labor Relations Board. With 45,000 votes cast, it was the largest private sector union election in the United States since 1941 at Ford Motor Co.

Kaiser Permanente is a major employer in the San Fernando Valley with large hospitals in Woodland Hills and Panorama City.

If workers had chosen a new union, it would have ended the current union contract with Kaiser, which went into effect in October.

“The vast majority of us love our union and our contract, and that’s why the vote was so lopsided,” said Lucy Rojas, a receptionist at Kaiser Woodland Hills, in a statement released by SEIU. “Now that the election is over, it’s time for all of us – no matter which side we supported – to put aside our differences.”

NUHW was founded by former SEIU officials and is affiliated with the California Nurses Association.