There's a continuing news story that I hear quite a lot about, and that would be the continuing claim that contaminants in vaccines, such as the preservative chemicals, are the cause of an ever-increasing stream of autistic children. Or even the very vaccines themselves. I'll try to cover this as neutrally as possible.
Autism is a developmental disorder in which a person does not develop socially, communicates poorly, values their own inner experience far over social consensus (and possibly even over the external world entirely), and has only a few interests that they follow obsessively. Having autistic children is quite distressing to the parents, since their child doesn't respond to social signals like hugging, and often ignore the parents entirely in favor of manipulating objects. Autism is a spectrum disorder, meaning that there are varying amounts of it, a person could be only a little autistic, very autistic, somewhere between those two, or not at all.
Autism is first noticeable in early childhood. At an age where children first start talking, the child does not talk. The child moves strangely, and insists on playing in a few ways over and over again. Upon being directed to another game, the child will return to their own preferred method instead.
The disorder has been known for long enough to watch people grow into adulthood with it. Adults with more minor autism often intellectually learn the social skills needed to succeed. They have been known to have trouble with relationships, as they had a late start with social skills, and to often be strangely good at art, animal management, or some extreme talent based on their interests. They are often described as reclusive, eccentric, odd, and obsessive.
Parents of autistic children have been frantically searching for a cause that they can blame it on, since when this disorder was first discovered, it was blamed on the child's mother being cold and unemotional. Some parents fear that this is still how it would be understood. Vaccines have often been blamed, since the first major vaccine cluster is usually issued around the same time that the disorder becomes apparent. Since one of the common preservatives used during the time when autism was first discovered included Mercury, a substance known to cause brain damage, the Parents blamed the vaccine for the condition of their child.
The preservative, thimerosal, was quickly removed from vaccines, but no change was observed in the rate of birth of autistic children, which only increased. The increase was particularly noted in silicon valley, in which many geeky people had settled and begun to raise their family with other geeky people. Nerdiness may be a very slight form of autism.
Autism very likely has some genetic component, since geeky people are more likely to product autistic children. Food may also cause or aggravate the symptoms, as Autistic people have been noted to also have any number of gastrointestinal disorders co-morbidly (that is, together with the autism in a way that suggests a link), and opioids (like poppy and sesame seeds) have been noted to worsen symptoms in one group studied, which seems to suggest that a digestive or metabolic defect may be at hand.
Although many parents continue to claim that vaccines are causing their children's problems and are doing their best to discourage vaccines, this is a bad idea. Vaccines are reducing the rate of disease propagation in general. If everyone ceased vaccination, disease would spread very easily. This problem suffers from the "free rider" problem in that the activist parents who refuse to vaccinate their children do not experience the negative effect of infect-able children because most people do vaccinate their children, which stops diseases before it reaches the infect-able.
While Autism has no cure, cognitive therapy has granted many people who have it a normal healthy life. And some people who have it are very strange indeed, but they seem happy enough.