Tjugum joins next month from an associate director position at Ogilvy.
John Lotspiech has also left Ogilvy, where he was a senior account manager, to join WS as an account director.
Other hires unveiled by WS this week include Helen Laurence, who has joined as an account manager. She was previously a senior account executive at Virgo Health PR.
Katy Davidson, a former account manager at Shire Health London, has joined WS as an account manager. Meanwhile, Tom Mardling, a former senior account executive at Ozone, joined last week in the same role.
The WS London healthcare team now numbers 31.