A Danish-led trial that would withhold the hepatitis B birth-dose vaccine from half of 14,000 newborns in Guinea-Bissau (a small, poor West African country with one of the world's highest hepatitis B rates) for their first six weeks has won approval from a University of Southern Denmark ethics committee and from Guinea-Bissau officials. Four committee members resigned in protest, and critics say the design deliberately exposes infants to a preventable disease that can cause lifelong liver damage, while the US health secretary, Robert F Kennedy Jr, has praised the research and the US CDC reportedly set aside $1.6m for it. The case matters because it tests international research ethics standards and reflects the Trump administration's push to question routine vaccine recommendations, even as the WHO advises giving the vaccine at birth.