Jefferson (main picture) will work with clients including Joint Investment Forum, BNY Mellon, Schroders, Henderson Global Investors and M&G Investments. She previously worked for the Royal Institute of British Architects and the Lawn Tennis Association.
"I was so impressed by their professionalism, passion and enthusiasm that I have been waiting for the right opportunity to join the team permanently ever since," she said.
Vanderbeck will work across the agency's portfolio of corporate clients. She spent five years with Prime, a full-service events agency in Vancouver and has also freelanced for Powwow.
"I moved to London to expand my career within the events industry and I feel very fortunate to now be part of a team as fun, creative, innovative and exciting as Powwow," she said.