Janzen, the 1993 and 1998 U.S. Open winner, has a virus. He has played in every British Open since 1991, but has never finished better than a tie for 24th. Last year, he missed the cut at the Old Course in St. Andrews, Scotland.
Last month, Janzen missed the cut at the U.S. Open after being penalized for using a towel to absorb moisture from the ninth fairway before replacing his ball that was in play.
No reason was given for Triplett's decision to skip the tournament. He finished in a tie for 60th last year in just his second trip to the British Open.
Notah Begay III, the Native American who played in the British Open for the first time at St. Andrews last year, withdrew last week due to a bad back.