Neutralising antibodies (factor IX inhibition)* Hypersensitivity/ allergic reactions; such reactions may include anaphylaxis*, bronchospasm/ respiratory distress, hypotension, angioedema, tachycardia, chest tightness, generalised urticarial, hives, rash, burning sensation in jaw and skull, chills (rigors), tingling, flushing, lethargy, restlessness, dry cough/ sneezing