Doxycycline for Prevention of Spirochetal Infections: Status Report.

Important human infections caused by spirochetal microorganisms include Lyme disease, syphilis, leptospirosis, and tick-borne relapsing fever. Doxycycline prophylactic regimens have been shown to significantly reduce the risk for developing all of these infections in potentially exposed individuals, which is highly clinically relevant as no vaccines to prevent these infections in humans are currently available. Additional data, however, are needed to define more precisely the level of efficacy of the doxycycline prophylactic regimens, especially for Lyme disease and syphilis, infections that can be potentially prevented by a single 200-mg dose of doxycycline given within 72 hours postexposure.