The most common side effect seen with biologics is pain and rash at the injection site. This occurs in less than 30% of patients. Since biologics given by infusion (in the vein) have the potential to cause an allergic infusion reaction. Symptoms of infusion reactions include flu-like illness, fever, chills, nausea, and headache.
As with any drugs that suppress the immune system, biologic therapy poses some increased risk to infections and other diseases. People taking biologics should seek immediate medical attention if they develop persistent fever or unexplained symptoms. Vaccinations that prevent infections should be considered prior to taking biologics. While taking biologic medications people should not receive live vaccines.
Biologics may also cause some chronic diseases that are dormant (such as tuberculosis) to flare, and they are not recommended for people with multiple sclerosis and other conditions such as severe congestive heart failure. All patients should be skin tested for tuberculosis prior to starting biologics, and many are also tested for chronic hepatitis.