Harrison's right knee was hurt in the Heineken Cup match against Toulouse at Hughenden on January 7 and he has now had an operation to repair ligament and cartilage damage.
He is looking to return to fitness in time for the Celtic League match against Cardiff Blues at Hughenden on Easter weekend at the end of March or the Stradey Park game against Llanelli Scarlets two weeks later.
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland