The American CDC on vaccines and autism

For many years, the CDC’s vaccine-safety pages stated clearly that vaccines do not cause autism and used that phrase as a concise summary of a large evidence base. The earlier material explained that multiple large epidemiologic studies from several countries, along with reviews by the Institute of Medicine/National Academies and other expert bodies, had consistently found no association between autism spectrum disorder and MMR, thimerosal-containing vaccines, or the number and timing of routine childhood vaccines. The message to clinicians and the public was categorical: available data did not support a causal link, and vaccines were described as safe and essential for preventing serious infectious diseases. In this framing, residual scientific uncertainty was acknowledged only in a very general sense, while the bottom-line communication was that parents need not worry about autism as a vaccine risk. In the newly revised text, the CDC retains historical references to past reviews but now asserts...