Unionized workers at Merck & Co. Inc.'s Montgomery County plant, where the drug company is making its new cervical-cancer vaccine and other key products, have ratified a three-year contract containing a no-layoff clause.

In a statement yesterday, the United Steelworkers said 70 percent of the members of Local 10-86 had voted for the contract Monday. The steelworkers' union, which absorbed the former chemical workers' union at the plant, represents roughly 1,800 of the approximately 10,000 employees at Merck's huge West Point complex.

Merck did not comment on the new pact, which will replace one that expires today.

The union said Merck, under the contract, had pledged there would be "no layoffs" of union members at West Point. The company made the promise while it is slashing positions and outsourcing work worldwide, although it also has said no cuts were planned at West Point.

On one contentious issue, the union also said the company had agreed to eliminate time clocks in its West Point facilities "on a trial basis." Instead, employees will log hours themselves, it said.

The contract "will help to maintain seniority rights for our local members. It enhances our wages and other benefits. And it will go a long way toward solidifying the position of the West Point facility within Merck," Charles Fickert, the local union president, said in a statement.

The union said each of its members would receive a $4,500 "signing bonus" and a 3.5 percent raise in 2007, 2008 and 2009. It said Merck also had agreed to increase its contribution toward medical benefits for the USW members by $4.5 million immediately, and by an additional 11 percent each year of the agreement.

"The result is that it's unlikely any USW member will pay more for medical insurance for the life of the contract, a significant benefit at a time of skyrocketing health-insurance costs," the union said.

It said the new pact provided an "improved benefit and pay package" for workers opting to retire early and assured "premium pay" for any time worked over 40 hours a week. It also creates a full-time union safety representative.

The pact takes effect as Merck tries to recover from troubles stemming partly from its 2004 recall of the pain reliever Vioxx. Its cancer vaccine and new diabetes treatments helped Merck's share price rise last week to $52.63, its highest in more than three years.

It was down 1.25 percent, or 65 cents, at $50.79, in trading yesterday.