From To Save America (rev. ed., 2011, pp. 142-143):
But perhaps no anti-scientific argument is more dangerous today than the claim put forward by radical environmentalists, most notably Robert F. Kennedy Jr., that childhood vaccinations can cause autism. Numerous peer-reviewed studies have disproved this connection. Moreover, the Lancet, a prominent British journal that published a 1998 study confirming a vaccination-autism connection, recently retracted the study, whose findings had already been repudiated by ten of its thirteen co-authors.
Yet some parents, worried by these rumors, have stopped vaccinating their children, endangering public health.
Note, however, that some on the right have also embraced the vaccine theory. Most notable is Gingrich's former colleague, Rep. Dan Burton (R-IN).