Prophylaxis is the regular infusion of clotting factor concentrates in order to prevent bleeding.

The idea of prophylaxis came from the observation that people with moderate or mild hemophilia (who have clotting factor levels of 1% or more) rarely experience spontaneous bleeding. They also have less joint damage than people who have severe hemophilia.

Did you know?
Prophylaxis will not help repair joints that are already damaged.

However, it will decrease the frequency of bleeding,may slow progression of joint disease, and may improve quality of life.
Doctors believed that if they could keep minimum factor levels around 1% with regular infusions of clotting factor concentrates, they may reduce the risk of bleeding and prevent joint damage.

Since then, important studies have shown that children who receive prophylaxis do have fewer bleeds and healthier joints.

Prophylaxis is now the goal of treatment for people with severe hemophilia, allowing them to remain active and participate more fully in daily life.

Resource: https://www.wfh.org/en/abd/prophylaxis/what-is-prophylaxis