- Tick-borne relapsing fever (TBRF) is endemic to Israel. Since 2004, the Israel Defence Forces (IDF) has mandated the prophylaxis of tick-bitten subjects with a five-day doxycycline course. We examined the safety and effectiveness of this policy in preventing TBRF. We analyzed the records from January 2004 to January 2007, and identified all reported events of tick bites or TBRF cases. Data were available on 27 events in which 816 soldiers have undergone physical examination following exposure, and seven TBRF cases were recorded in this group-an attack rate of 0.86% compared with the expected rate of 5.34% from previous army data (relative risk [RR] = 0.16). Of those screened, 128 (15.7%) had tick-bite and were intended for prophylaxis, of which four TBRF cases occurred-3.13% attack rate compared with an expected rate of 38.4% in these bitten individuals without prophylaxis (RR = 0.08, number needed to treat = 3). In all cases in which screening and prophylaxis were provided within 48 h of tick bite, complete prevention of TBRF was achieved. No cases of Jarisch-Herxheimer reaction (JHR) was recorded. Tick-bite screening and prophylactic treatment with doxycycline in endemic areas is a practical, safe, and highly effective policy for preventing TBRF.