One of the most prominent medical related conspiracy theories out there is that pharmaceutical companies are covering up an alleged connection between vaccines and autism. They claim that the reason why these pharmaceutical companies are allegedly covering up this alleged connection is because the pharmaceutical companies make to much money off of vaccine sales to take them off the market.
It's true, pharmaceutical companies do make money off of vaccines, but in terms of total profit of what these companies make off of other things, like pain medicine, or stuff to treat a cold, vaccines are only a small percentage of the total profit they make, which tends to happens when you mass produce a product that is not only cheap to produce, but also only needs to be taken two or three times in a life time.
The reason why so many people believe that vaccines cause autism is because of a highly discredited and fraudulent British medical article written by Andrew Wakefield. The medical article he published was so flawed, and so fraudulent, that Wakefield is no longer allowed to practice medicine in Great Britain, and many of his critics have even called for his arrest due to all the deaths caused by people not getting their children vaccinated because of the article he wrote. Yet still he asserts that there is a "cover up" and for some reason he claims that not as many children died of the measles as what has been reported, even though all the research on autism says vaccines are not the cause of autism.
The fact remains is that this is probably one of the most dangerous forms of medical quackery to date, and there have been thousands of children who have gotten sick, and even died from stuff that could have easily been prevented by a simple shot.
There is no proof that vaccines cause autism, in fact vaccine manufactures stopped putting mercury preservatives in their vaccines over 15 years ago, thus making them even safer. So far, all fingers point to genetics as being the cause for autism, which isn't very surprising, because certain genetics problems can also be the cause of many other neurological problems and mental handicaps, and the reason why there is an increase of children being diagnosed with is because there is an increased awareness of autism, and an increase of what is considered symptoms of autism. In fact not vaccinating your child may cause them to get a disease that may leave them with neurological problems, or leave them mental handicapped, if it doesn't out right kill them.