In a relatively unusual event, federal health officials called a news conference this week in an attempt to affirm the safety of vaccines.
This came among the growing concern of some parents who allege that vaccines can cause autism.
A rally by autism activists is planned this week in front of the U.S. Capitol on to emphasize their belief that the government has concealed evidence linking autism to a mercury-based product once used in vaccines.
The activists will also demand more research into what they consider is the growing problem of autism.
Dr. Julie Gerberding, director of the U.S. Centers for Disease Control and Prevention (CDC) , said at the news conference, that there has been renewed interest in the issue of vaccine safety, particularly on whether the preservative thimerosal, may be linked to the occurrence of autism in children.
Unfortunately, autism is often diagnosed between the ages of about 18 months and four years, which is about the time that toddlers and young children are getting their vaccinations.
To date, no reports, and that includes a review of all the studies from the independent Institute of Medicine, have found evidence that vaccines cause autism.
Some groups of parents however allege a cover-up, and have resisted vaccinating their children.
This has led to outbreaks of diseases such as measles and whooping cough in Britain, the Netherlands and elsewhere.
These parents believe there is evidence, that at least some children, are sensitive to mercury, including the mercury in thimerosal.
In the United States Thimerosal is no longer used in childhood vaccines.
At the news conference CDC officials, as well as representatives of the National Institutes of Health, American Medical Association, American Academy of Pediatrics, and the Food and Drug Administration, made it clear they believed some of the groups were relying on incomplete information.