One of the Oxford rowers was carried out of the boat after he collapsed at the end of the race.
Medic Alexander Woods, 27, was lifted from the bow.
Because of this, there was no presentation to the winning team.
British Olympic Association chairman Lord Moynihan has said that security chiefs "can never completely remove" the threat of disruption.
The 158th University Boat race had to be halted after a protester swam towards the boats.