Besides the author himself, there is an independent non-profit organization speaking in support of him. Do you think the researches conducted have excluded the possibility that there is a correlation between vaccines and autism or not? My answer to it is no, so the question is still there.
I'm not a conspiracist, but did you see the news at
http://www.theaustralian.com.au/news/drug-company-drew-up-doctor-hit-list/story-0-1225693586492? That may tell you that the trial is not that simple. And there are other two authors who did not renounce the paper. So keeping an eye open on the things behind the stage is not meaningless in this case.