Subjects vaccinated with three doses of LYMErix or placebo at months 0, 1 and 12 were observed for 20 months after the first injection (January 1995 through November 1996). The primary endpoint of the trial was the incidence of definite Lyme disease after two doses of vaccine. Each subject was actively followed for symptomatic disease during the entire observation period and was assessed for possible asymptomatic infection (as evidenced by IgG Western blot seroconversion) at months 12 and 20.

Definite Lyme disease

In the pivotal efficacy trial, definite Lyme disease was defined as clinical manifestations (erythema migrans, neurologic, musculoskeletal or cardiovascular involvement) with laboratory confirmation (positive culture for B. burgdorferi from skin biopsy; positive polymerase chain reaction [PCR] result for B. burgdorferi from skin biopsy, synovial fluid, or CSF; or IgM or IgG Western blot seroconversion) as defined by CDC/ASTPHLD criteria.¹¹

Post-second dose efficacy was measured beginning at 4 weeks following the second dose through to month 12. Post-third dose efficacy was measured from the third dose through to month 20.

Prevention of Definite Lyme Disease: Vaccine efficacy against definite Lyme disease was 78% (95% CI: 59% to 88%) after three doses of vaccine administered according to protocol (13 cases among 4,765 subjects in the vaccine group; 58 cases among 4,784 subjects in the placebo group). Vaccine efficacy against definite Lyme disease was 50% (95% CI: 14% to 71%) after two doses of vaccine administered according to protocol (20 cases among 5,148 subjects in the vaccine group; 40 cases among 5,166 subjects in the placebo group).

Asymptomatic B. burgdorferi infection

In the pivotal efficacy trial, subjects were defined as having asymptomatic infection when, in the absence of recognizable clinical symptoms, IgG Western blot seroconversion occurred either between months 2 and 12 of the first year, or between months 12 and 20 of the second year.

Prevention of Asymptomatic Infection: Vaccine efficacy against asymptomatic B. burgdorferi infection was 100% (95% CI: 30% to 100%) after three doses of vaccine administered according to protocol (0 cases among 4,765 subjects in the vaccine group; 13 cases among 4,784 subjects in the placebo group). Vaccine efficacy against asymptomatic B. burgdorferi infection was 83% (95% CI: 25% to 96%) after two doses of vaccine administered according to protocol (2 cases among 5,148 subjects in the vaccine group; 12 cases among 5,166 subjects in the placebo group).

Possible Lyme disease

In the pivotal efficacy trial, possible Lyme disease was defined as a flu-like illness (fever, chills, fatigue, headache, joint or muscle aches) with IgM or IgG Western blot seroconversion, or physician-diagnosed erythema migrans with negative laboratory results.

Prevention of Possible Lyme Disease: Following the threedose course of vaccine administered according to protocol, efficacy was 48% (95% CI: 1% to 73% ) against possible Lyme disease. Fourteen of the subjects in the vaccine group developed a possible case of Lyme disease, compared to 27 placebo recipients. Following two doses of vaccine administered according to protocol, the vaccine efficacy against possible Lyme disease was 21% (95% CI: -45% to 56%). Nineteen subjects who received two doses of vaccine developed possible Lyme disease, compared to 24 placebo recipients.

The data regarding flu-like illnesses due to possible Lyme disease may be confounded by possible cross-reactivity and/or co-infection with Ehrlichia, which may cause a flu-like illness and false-positive IgM Western blot for B. burgdorferi.¹⁷

Lyme Disease Manifestations and Laboratory Diagnosis in the Efficacy Trial: The clinical presentation of the 131 cases of definite Lyme disease was as follows: erythema migrans, 128 (32 vaccine, 96 placebo); arthritis, 1 (vaccine); trigeminal neuralgia, 1 (placebo); and facial palsy, 1 (placebo). Of the 128 cases with erythema migrans, additional presenting clinical manifestations included: facial palsy, 3 (1 vaccine, 2 placebo) and trigeminal neuralgia, 1 (placebo). The duration of erythema migrans was similar for both vaccinees and placebo recipients.

Bookmark this page: