On March 24, 1900, Clara Maass signed a consent document and volunteered to be bitten by yellow-fever-infected mosquitoes for Walter Reed's research, for $100 in gold.
On March 24, 1900, Clara Maass signed one of the earliest known informed-consent documents in American medical history and volunteered to participate in Walter Reed's U.S. Army Yellow Fever Commission experiments in Havana, Cuba.
The experiments sought to prove Cuban physician Carlos Finlay's theory that yellow fever was transmitted by the Aedes aegypti mosquito rather than through direct contact or contaminated materials, as had long been believed. Volunteers, including American soldiers, Spanish immigrants, and eventually Maass, agreed to be bitten by mosquitoes previously fed on yellow fever patients, in exchange for payment — in Maass's case, $100 in gold, along with the promise of immunity from further risk of the disease.
Her participation was extraordinary: as a nurse who had cared for yellow fever patients during the Spanish-American War, she understood viscerally the disease's lethality, yet she volunteered anyway, motivated by both financial need and a conviction that the research could save countless lives, including those of fellow nurses and soldiers stationed in tropical postings.
This consent document, though rudimentary by modern standards, represents an important, early milestone in the history of medical ethics and human-subject research, predating later formalized codes such as the Nuremberg Code by decades. Maass's willingness to subject herself repeatedly to infection over the following months would ultimately cost her life, cementing her as one of the defining figures in the ethical history of medical experimentation.