Lyme disease is the most common tick-borne infection in the United States, with more than 12,000 cases reported annually (1). The disease is characterized by a rash (erythema migrans) and various systemic (nervous, cardiac and musculoskeletal) manifestations; clinical manifestations of Lyme disease were reviewed recently (2). Most cases of Lyme disease in the United Sates are reported from the northeastern, mid-Atlantic and upper north central states, and from a part of northwest California. Lyme disease is caused by the spirochete Borrelia burgdorferi, and it is transmitted by the deer tick Ixodes scapularis in the eastern and mid-western states, and Ixodes pacificus in the Pacific coast states. Transmission occurs primarily through bites acquired during the nymphal stage of the life cycle of the ticks, which feed predominantly in the late spring and early summer. Two vaccines that protect against Lyme disease have been developed; one has been licensed for use in Canada recently. Answers to common questions about the Lyme disease vaccine follow.