A new study in the medical journal The Lancet reports that more than 100 United States government health datasets were altered this spring without any public notice. The authors warn that hidden edits of this kind can ripple through public health research and erode confidence in federal data. These government datasets form the backbone of countless psychology, sociology, and public health projects. Public health officials may then allocate resources on a faulty premise, and medical guidelines that depend on demographic baselines can drift off target. Independent groups already mirror many federal datasets on private servers, and individual investigators can save local copies of files they intend to analyze.