PEARL RIVER – Pfizer, which had considered shutting down its Pearl River facility, will be keeping it open as one of its five worldwide research and development centers, but it plans layoffs.

Rockland County Executive C. Scott Vanderhoef said Friday that Pfizer officials had warned of a possible 40 percent reduction in employees in R&D and additional job losses in its manufacturing division. The transition is scheduled to start by the end of this year and should be completed by 2011, Pfizer officials told him.

“It’s a mixed blessing,” the county executive said. “On one hand, we’re relieved to learn that the Pearl River plant will remain open and productive as an R&D center, which has been the company’s mainstay since its creation. The potential loss of jobs, however, would be burdensome for the county and Town of Orangetown during this difficult economic climate.”