WASHINGTON — In the space of a week, Chris Vaccaro was furloughed from his government post, called back and then furloughed again in head-spinning events that left him feeling like a human yo-yo.

“It’s been odd having to switch your mindset off and on,” said Vaccaro, communications director at the National Oceanic and Atmospheric Administration.

Vaccaro is among thousands of federal employees whose status changed from nonessential to essential at some point over the course of the partial government shutdown, now in its third week. Agencies from the Federal Aviation Administration to the Centers for Disease Control and Prevention have recalled some of their workers to deal with issues.

For Vaccaro, it happened Oct. 3, as government agencies were preparing for the threat posed by Tropical Storm Karen along the Gulf Coast. But once the storm dissipated two days later, he was back on his couch at home. About 200 furloughed Federal Emergency Management Agency workers were similarly called back to deal with the storm, but at least half were furloughed again.

The number of federal workers who have been recalled wasn’t specified. When the shutdown began, about 800,000 of 2.1 million workers were furloughed.