Two recent events -- a federal court ruling in favor of the family of a Georgia girl with an autism-like disorder, and Republican Presidential nominee John McCain’s statements relating autism to vaccines -- have stirred up the ongoing controversy regarding childhood vaccinations and autism.

Hannah Poling, 9 years old, has an unusual disorder of the mitochondria in her cells. The court determined that the 5 shots she received at the age of 19 months exacerbated the disorder, resulting in brain dysfunction with autistic spectrum features. As a consequence, her family was awarded compensation from the National Vaccine Injury Compensation Program, which is funded by a tax on vaccines. The director of the CDC responded in a telephone interview, “… the government has made absolutely no statement about indicating that vaccines are a cause of autism.”

John McCain was at a town hall meeting in Texas when the mother of a boy with autism asked his opinion about the court ruling. According to ABC News’ Bret Hovell, he replied “… there’s strong evidence that indicates that it (autism)’s got to do with a preservative in vaccines.” (McCain was referring to the mercury-based preservative thimerosal, which was removed from vaccines in 2001. Small amounts are still present in some flu shots, but for seven years thimerosal has been absent from standard childhood immunizations, and the incidence of autism continues to rise) Although McCain also stated that scientific opinion is divided, his own opinion, which goes against the dogma of the medical establishment, has been hailed as an important step towards an admission of responsibility.

Because of these events, more parents are questioning the safety of childhood vaccines. In the United States, children must be vaccinated in order to attend public (and most private) schools. For example, the state of Texas requires children in public school to receive the following immunizations: diphtheria-tetanus-acellular pertussis (DTaP), hepatitis A and B, haemophilus influenzae b (Hib), measles-mumps-rubella (MMR), pneumococcal (PCV), polio, and varicella (chicken pox). Although most states allow exemptions for religious and medical reasons, and a few for philosophical reasons, some states do not allow any exemptions. These strict requirements have contributed to the increase in the number of families who choose to home school or to send their children to religious schools that are not subject to the vaccine regulations.

The overall effect is that ever-increasing numbers of children are unimmunized. What impact might this have on public health? Since anti-vaccination movements have also arisen in other countries, it is useful to look at data from those countries’ “experiments” in reduced vaccination rates to predict possible outcomes in the U.S.

As an example, the use of pertussis (whooping cough) vaccine fell dramatically during the mid-1970’s in Sweden and the United Kingdom. The decrease in vaccination was accompanied by a significant increase in the incidence of whooping cough. Pertussis is highly contagious, with 70-100% of exposed, unimmunized individuals becoming ill. It is also potentially deadly, especially in infants. Epidemics of whooping cough occurred and many children died.

Some childhood illnesses that are now preventable by vaccine are not typically dangerous for otherwise healthy children, but can cause serious complications when adults contract them. Because immunizations wear off over time, adults over 30 today are susceptible to those illnesses they were vaccinated against in childhood, such as pertussis, polio, measles, mumps, and rubella. In adult males, mumps can attack the testicles, causing them to shrivel and blacken, producing sterility. If a pregnant woman contracts rubella during her first trimester, the risk of serious birth defects is very high. Elderly individuals, those with chronic diseases or compromised immune systems, and the many people who take immunosuppressive drugs are particularly vulnerable when exposed to childhood diseases, and many die of the disease itself or from complications.

There are some medical conditions which contraindicate vaccination, such as chronic illnesses or chemotherapy. It is also important for governments to respect the religious rights of groups that believe vaccination is immoral. However, anti-vaccinationists should be well-informed about the possible consequences – to themselves, as well as to those around them – when they choose not to have their children vaccinated.