So far, mainstream researchers have not found a direct link between vaccine injury and autism. In fact, multiple studies have shown no link at all. These studies range from large scale epidemiological studies to smaller biological studies - and all seem to come up with the same answer.
Meanwhile, though, several unconventional researchers believe they've found strong links between vaccine injury and autistic symptoms. While few mainstream thinkers believe these studies hold water, many parents and some doctors support the findings wholeheartedly.
One reason for some people's certainty that vaccine injury can cause autism is the Hannah Poling case which came before the Vaccine Court in 2008. In essence, young Hannah received multiple vaccines in a single day, and later developed autistic symptoms. The Court awarded the Polings a settlement, and the case (and the Polings) became "proof" of a connection between vaccine injury and autism.
The Poling case, however, is not typical. Hannah had an underlying mitochondrial disorder, a condition which some feel made her unusually susceptible to stress from vaccines. Hannah developed worsening of her global encephalopathy, which includes autistic symptoms, at a typical age for her disease. Infections and fever are known to worsen such conditions but there is no clear evidence that vaccines cause similar worsening. It is for this reason that vaccines are particularly important for such patients to protect them from vaccine preventable disease, many of which are still quite common.
Sources:
Lerman-Sagie T, Leshinsky-Silver E, Watemberg N, Lev D. Should autistic children be evaluated for mitochondrial disorders? J Child Neurol. 2004 May;19(5):379-81.
Lombard J. Autism: a mitochondrial disorder? Med Hypotheses. 1998 Jun;50(6):497-500.
Oliveira G, Diogo L, Grazina M, Garcia P, Ataíde A, Marques C, Miguel T, Borges L, Vicente AM. Mitochondrial dysfunction in autism spectrum disorders: a population-based study.Dev Med Child Neurol. 2005 Mar;47(3):148.
Poling JS, Frye RE, Shoffner J, Zimmerman AW. Developmental regression and mitochondrial dysfunction in a child with autism.
J Child Neurol. 2006 Feb;21(2):170-2.
"Recommendations of the Advisory Committee on Immunization Practices (ACIP) and the American Academy of Family Physicians (AAFP." February, 2002.
