Context: For centuries, homeopathic practitioners have claimed that serially agitated dilutions of infectious agents (called "nosodes") are effective in the prevention of infectious disease. However, no rigorous tests of this claim have been performed.
Objective: To test whether a nosode of Francisella tularensis-infected tissue could protect from subsequent challenge with this pathogen in vivo.
Design: Experimental laboratory test.
Setting: A P3 containment laboratory at an infectious disease research facility.
Participants: 142 male C3H/HeN specific, pathogen-free mice.
Intervention: Six levels of a nosode prepared from tularemia-infected tissue were produced. All exposures were below the lowest level at which a classical vaccination response was expected. The nosode and dilutent control solutions were administered orally (.03 mL, 3 times per week) for 1 month before and after challenge. Animals were challenged with a potentially lethal dose (LD50 or LD75) of F tularensis, then evaluated for time of death and total mortality.
Main outcome measures: Mortality and time to death.
Results: In a series of 15 trials (n = 142), the tularemia nosode consistently produced increased mean times to death. All but 2 of 15 trials showed reduced time to death in the nosode group and decreased mortality compared with controls. Protection rates averaged 22% over controls compared to 100% protection by standard vaccination.
Conclusions: This study found partial protection from a nosode of tularemia in dilutions below those expected to have protective effects, but not as great as those produced by standard vaccination. If homeopathic nosodes can induce protection from infectious agents for which vaccination is currently unavailable, they may provide an interim method of reducing morbidity or mortality from such agents.