| Summary: | We extend recent conversation about the ethics of human challenge trials to tuberculosis (TB).
TB challenge studies could accelerate vaccine development, but ethical concerns regarding risks
to trial participants and third parties have been a limiting factor. We analyze the expected social
value and risks of different challenge models, concluding that if a TB challenge trial has between
a 10% and a 50% chance of leading to the authorization and near-universal delivery of a more
effective vaccine three to five years earlier, then the trial would save between 26,400 and
1,100,000 lives over the next ten years. We also identify five important ethical considerations
that differentiate TB from recent human challenge trials: an exceptionally high disease burden
with no highly effective vaccine; heightened third party risk following the trial, and, partly for
that reason, uniquely stringent biosafety requirements for the trial; risks associated with best
available TB treatments; and difficulties with TB disease detection. We argue that there is good
reason to consider conducting challenge trials with attenuated strains like BCG or attenuated
M.tb.
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