The US government issued a formal apology for a 1940s study on the efficacy of penicillin in which as many as 695 Guatemalan prisoners, insane asylum inmates, and soldiers were infected with syphilis.

Study subjects were encouraged to pass the infection to others, and about a third never got fully treated, MSNBC reports.

John Cutler, one of the researchers involved in that study went on to help conduct the infamous Tuskegee syphilis experiment, a long-term study of syphilis progression in African American sharecroppers in Alabama in which researchers deliberately did not treat subjects even after penicillin became available. Both studies received funding from the Public Health Service (now the Department of Health and Human Services).

The Guatemalan study was unearthed by Susan Reverby, a professor of women’s and gender studies at Wellesley College in Wellesley, Massachusetts.

Her paper on the subject is due to be published in the January issue of the Journal of Policy History. She also took the unusual step of alerting the US government to her findings before publishing them, Reuters reports.

A statement issued by Health and Human Services Secretary Kathleen Sebelius and Secretary of State Hilary Clinton promised “a thorough investigation into the specifics of this case from 1946.”

The statement goes on to say: “The sexually transmitted disease inoculation study conducted from 1946-1948 in Guatemala was clearly unethical. Although these events occurred more than 64 years ago, we are outraged that such reprehensible research could have occurred under the guise of public health. We deeply regret that it happened, and we apologize to all the individuals who were affected by such abhorrent research practices. The conduct exhibited during the study does not represent the values of the United States, or our commitment to human dignity and great respect for the people of Guatemala. The study is a sad reminder that adequate human subject safeguards did not exist a half-century ago.”

Image: Wellesley College