The U.S. Department of Health and Human Services confirmed a planned randomized study in Guinea‑Bissau that will investigate health effects of neonatal hepatitis B vaccination, despite ethical concerns raised by scientists and international bodies. The five‑year trial would randomize newborns to receive the vaccine at birth or according to local standard practice, with HHS asserting the study addresses evidence gaps and will meet scientific and ethical standards. Critics pointed to design elements and comparisons with historical unethical trials; HHS maintained the protocol aligns with local policy and noted the trial is intended to inform global vaccine guidance. The confirmation rekindles debate over trial design, informed consent, and research governance in low‑resource settings.