Earlier this week the world's population pass the six billion mark. What -- so staggering about that number is that most of the growth -- happened during this century. There were only about one point... See More
Earlier this week the world's population pass the six billion mark. What -- so staggering about that number is that most of the growth -- happened during this century. There were only about one point six billion people as the twentieth century dawned. And when you consider -- ruthlessly efficient we've been -- killing one another. An hour in China Stalin in the Soviet Union -- throughout Europe poll -- in Cambodia. Well you have to ask yourself how in heaven's name we end this century with so many more people than we had at the beginning. More and better food. That certainly want to answer she usually improved medical care has to be another. Some of the diseases that used to wipe out thousands of people here in the United States alone measles smallpox diphtheria polio whooping cough. Have been effectively eliminated as threats to us and our children. And a major reason for that is the children today they receive as many as nineteen shots. For at least ten different diseases by the time the six years old. It is these vaccines as much as anything else that have lengthened our lifespan by an estimated average of nearly thirty years since 19100. Still even those precious life saving the life extending vaccines. Are believed by some to -- some serious risks and as Nightline correspondent John Donvan reports. It is those risks which you've been getting the headlines. These last few months. It's. Over the past year just what message have we open receiving about the safety of childhood vaccinations. In the winter we heard on ABC running -- doctor thinks the vaccination could have triggered his illness in this summer on NBC these cases -- Are extraordinarily rare. On an oftentimes. It's impossible to clearly identify that the vaccine. Is the culprit. This fall CBS. Mary Elizabeth Hagerty suffered a 45 minute long seizure shortly after receiving a DT. And also this fall CNN we can. Can't let down our guard. Is far is. Making sure that all our children are vaccinated. In short it is a conflicting message vaccines say the experts are -- diseases like polio smallpox and diphtheria. No longer scare Americans there is no evidence has the medical establishment. They're causing any harm. But Welling up from the public from parents spreading by word of mouth and passed along of course on the Internet are those frightening anecdotes of vaccinations that -- Do harm He was growing up -- in the world can He thought that shark does this incredible sense of frustration in the family. And autism face as -- 24 hours a day there's three of us. Walking distance with constituents and it scares me. Right now word of mouth says one vaccination may actually be causing autism. The suspect is MMR vaccination against measles mumps and about. The fear just will not done. Even though the one study that looked into it published in the respected journal the lancet last June. Says there is no evidence that autism rates are increasing because of MMR. But it's as though nobody read the report -- six weeks after the lancet study congress held hearings into the safety of MMR. And the news media kept raising the question of whether -- easily. We've seen this happen before the refusal by non experts parents or patients. To trust the word of people who are supposed to be the expert. Gulf war syndrome silicon breast implants these were cases where the doctors and researchers tried and failed to establish cause and effect. And when that happened the public suspected the experts just hadn't tried hard enough. It is the power of the anecdote the old cliche when you see the faces of the kids who have become sick after -- vaccination. That a picture is worth a thousand words. But do not dismiss what an anecdote may be trying to kill you says Barbara Fisher. Who believes her son suffered brain damage from a vaccination in 1982. You know the cornerstone of medicine has always again. Anecdotal evidence that is the first warning sign that something that there may be a cause and effect relationship between something that a physician does. And something adverse that happens. Information from. Fisher heads a Virginia based movement that has challenged the safety of vaccines and publishes a consumer's guide for parents. The operation has a bit of a David and Goliath complex Fisher feels that her work has been distorted. Ridiculed and demonized by certain members of the medical establishment who she says tried to dismiss her as an over emotional mom. But Fisher is not above a little demonizing either she believes there are people with bad intentions. Because I think those who have a vested interest -- in maintaining the status quo who would -- who would want to maintain the status quo of kids are at risk. I think that certainly the vaccine manufacturers who are in the business of making and selling vaccines. And -- obligation to their stockholders frankly is the bottom line all that aside fisheries organization. Is an example of -- people who have made themselves expert on complicated medical issues. They have also prove their point and a significant way thanks in part to their well informed lobbying congress in 1986. Passed a law providing compensation for kids harmed by vaccines. The fact that in recent years the DTP vaccine for diphtheria tetanus and pertussis was changed because there were concerns it could lead to brain damage. The fact that the CDC has suspended this year. The rotavirus vaccine which appeared to cause severe intestinal problems in infants. -- -- -- These changes suggest that parents and doctors who question the safety of -- -- are not just being paranoid. But the greater fear of most doctors. Is that parents will panic and stop giving their children vaccinated and that they say it could be a nightmarish step backwards. You don't -- whooping cough. Pertussis very much anymore it used to kill 9000 a year -- with the vaccine. And polio. It's been all but eradicated from our hemisphere since 1991. Because. Of a vaccine. There -- hospitals full of children and adults on -- -- which was the only -- these children and adults could -- because of polio when you see the real disease and this in front of you. That's when it becomes real we have done such a good job of vaccines. And eliminating diseases. That people forget what happens when you stop facts of. Let me be clear but one thing you're coming nowhere near calling for a banning vaccine for a boycott of -- now by parents absolutely -- act. We're simply saying you've got to take a look at -- You've got to achieve the balance. And you've got to make the policies more humane and you've got to always try to make the vaccine is -- for. Which any doctor will tell -- is their concern to. Safety is extremely important to I have three children immunized them. I wanted to show -- -- But the truth is even living as we do in the most medically advance society in history. A 100% safety and anything's still eludes -- -- -- -- -- all the time to achieve that mark. But when medicine fails when science cannot explain everything that's when we start listening to tragic anecdotes. Especially if you're the mother or the father of the child anecdote is about. I'm John Donvan for Nightline in Washington.
This transcript has been automatically generated and may not be 100% accurate.
'We're the Millers': Trailer
'We're the Millers': Trailer
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