Thanks to Stevie T for sending this link:
Dr. Andrew Wakefield, the lead investigator, brought international attention to the paper by saying he thought the MMR vaccinations were to blame. The assertions chipped away at confidence in vaccination.
It later emerged that Wakefield had been taking money from a lawyer suing vaccine makers. The results of his study couldn't be replicated. Most of Wakefield's co-authors later retracted the paper's interpretation of the data. The Lancet backed away from the paper in 2004, but defended its publication on the grounds it helped "raise new ideas."
In the retraction today, the Lancet editors wrote that it became clear parts of the paper are "incorrect."
What was the last straw for the Lancet? An investigation by the U.K.'s General Medical Council, which regulates doctors, found that Wakefield had acted dishonestly and irresponsibly.