The agency has recruited Jennifer Quinn, from her post as correspondent at Associated Press. She also worked at the Toronto Star in Canada.
Clew has also employed Lou Garrett, a writer with Vielife, a company which develops health promotion material for the NHS. She previously worked at News of the World.
The third recruit is under wraps, but it is understood the trio will work on selling stories into the media.
Two senior health journalists have joined agencies this year: former Daily Mail science correspondent Julie Wheldon went to Manning, Selvage & Lee, while Daily Telegraph medical editor Celia Hall joined Sante Communications.
Cew chairman Chris Mihill was previously medical correspondent at The Guardian.