A method is provided for treating human patients who have Lymes disease by using a psoralen compound, preferably administered in a dosage of 0.3 to 0.7 mg/kg, and activating same either in vitro or in vivo using electromagnetic radiation of a prescribed activating wavelength. The activation of the psoralen compound in the presence of a blood fraction from a patient suffering from Lymes disease produces a composition which will stimulate an effective immune response to the Lymes disease on the part of the patient.
