Those who question immunization have two main concerns. First, do the weakened viruses contained in the measles-mumps-rubella (MMR) vaccine increase the risk of autism? Second, are preservatives in the vaccine linked to the disorder? Passionate debate regarding these questions has moved from the world of science into popular media. Even celebrities are campaigning for and against immunization.
Parents want clear and accurate information. With apparent disagreements between the medical community and groups who have raised concerns about vaccination, what should parents believe? To make the best decisions about children, we must understand how this controversy developed.
Early warning signs of autism often appear between the ages of 12 to 18 months. They may include:
Such signs may appear around the time that children are receiving vaccinations, particularly the MMR, which is given at 12 and 18 months in Canada. However, many studies have shown that children who are not vaccinated are just as likely to develop autism.
The link between autism and the MMR vaccine was first reported in 1998, in a paper Dr. Andrew Wakefield and his colleagues wrote for the British medical journal The Lancet. It described 12 children who had gastrointestinal complaints such as diarrhea and abdominal pain. The children seemed to develop normally, but then lost skills.
Wakefield specialized in treating diseases of the digestive system. He thought a possible connection between autism and the MMR vaccination might exist. If inflammation in the gut led to toxins being absorbed through the digestive system, brain development might be affected. This could increase the risk of autism. Media coverage on his article was followed by lowered immunization rates in the United Kingdom.
However, before the children took part in Wakefield’s study, some of their parents had filed a lawsuit against vaccine manufacturers. Wakefield had received funds to assist them in their case. On learning this, The Lancet and 10 of the 12 co-authors of the paper withdrew their support, saying no link had been found.
Since that time, several other studies have been published. None have found that the MMR vaccine places children at higher risk of autism. Unvaccinated children are as likely to develop autism as vaccinated children. The timing of early signs of autism is the same in both groups.
Thimerosal is a preservative with a mercury base. It has been used to stabilize multi-dose vaccines. In 2001, Dr. Sallie Bernard suggested that exposure to thimerosal in vaccines may be a risk factor for autism. Other researchers have argued that there is very little overlap between clinical signs of mercury exposure and those of autism. Concerns were raised (but not proven) about mercury exposure possibly adding up in vaccines, foods and other sources. As a result, thimerosal has been withdrawn from childhood vaccines.
In Canada, most standard childhood vaccines (including MMR) have been free of thimerosal since 1992. The only exception is the infant Hepatitis B vaccine. Some versions still contain small amounts of thimerosal.
However, no research has directly linked thimerosal to increased risk of autism. In fact, several studies worldwide (including in Canada) have shown that rates of autism continue to rise even as thimerosal is removed from childhood vaccines.
In Canada, measles, mumps and rubella are currently rare since most children are immunized against them. If parents choose not to immunize their children, the rates of serious but preventable infections will rise. Throughout the world, measles kills 250,000 children per year. It leaves many millions more with serious disability, including blindness. In England, where Andrew Wakefield first did his controversial research, one in four children are not fully vaccinated with the MMR. This has led to increasing rates of serious measles infections.
Even with Canada’s high immunization rates, outbreaks of preventable infections still occur. The mumps virus causes fever, facial swelling, and in rare cases, infertility and serious brain injury. In November of 2007, an outbreak of mumps appeared among young adults in Alberta. Thirty-three cases in Calgary and 27 cases in Lethbridge were reported. This was a significant increase, compared to just six confirmed cases in Calgary for all of 2006. Vaccination plays an essential role in protecting the health of Canadian children.
As a parent, you want your child to be safe and healthy. You may be faced with contradicting messages about immunization and the risk of autism. It is important that you feel comfortable in talking to your health care provider about it. Your questions deserve respect. As a parent, you are responsible for making medical decisions on behalf of your child. Parents should be able to expect their health care providers to take their concerns seriously, and provide accurate information that parents can use to help make informed decisions.
Remember, overwhelming evidence exists that vaccines do not cause autism. You will also want to discuss the serious risk of preventable infections that could happen if your children are not immunized.