It’s quite unusual for me to write follow-up columns, but I had such an overwhelming response to my recent column regarding the disputed link between childhood vaccines and autism (search) that I felt this was one of those rare occasions that merits immediate further comment.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
Roughly 95 percent of my reader responses came from parents of autistic children angered by my column because they feel passionately that thimerosal (search)—a mercury-based preservative used in vaccines for over 60 years—causes autism. The other five percent came mostly from medical professionals who applauded the column because, like me, they advocate the mainstream medical opinion that thimerosal-containing vaccines aren’t related to autism.
Although this debate has raged for years, and will likely rage for many more, a decisive turn for many in the medical community came with the 2004 release of a definitive report from the National Academy of Sciences’ Institute of Medicine (search) which reviewed several decades worth of studies concerning a possible link between thimerosal and autism.
In addition to stating that it saw no convincing evidence of such a link, the IOM panel went one step further and recommended that no further research funding be directed toward trying to find one. That unusual recommendation carried a lot of weight since IOM review panels are thought of by medical professionals as the “gold standard” of scientific peer review.
Naturally, I sympathize a great deal with the plight of those parents who wrote to me since autism remains one of the most mysterious and devastating conditions known to medicine—both for the children who suffer from it and for their caregivers.
I certainly respect their search for answers. Yet at the same time I want to express in the strongest possible terms how important it is that parents not allow this controversy to frighten them away from getting routine vaccinations for their children.
A survey published in the November 2000 issue of the medical journal Pediatrics reported that 25 percent of all parents have serious concerns about some or all of the vaccines required in the standard immunization schedule.
Bowing to that fear, states such as <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Colorado and Oregon even offer parents the opportunity to refuse to have their children participate in the routine vaccination schedule. As one might expect, in communities like Boulder, Colo., where some parents have opted out of vaccinating their children, diseases like whooping cough are making an alarming comeback.
It’s well-known that the failure to get children vaccinated can lead to disfiguring, disabling and even fatal diseases. But what parents may be less aware of is that opting out of the standard immunization schedule isn’t simply a matter of individual choice—it also has profound implications for public health around the world.
Epidemiologists refer to “herd immunity” (search) as a population’s overall resistance to epidemics once that population achieves a 90 percent vaccination rate. Among a “herd” of 90 percent immune individuals, a non-immunized person enjoys a fairly low risk of contracting whatever deadly communicable diseases to which the “herd” is immune.
As the herd’s immunity falls below 90 percent, however, not only do the non-immunized individuals face a greater danger of becoming ill, but the greater availability of more non-immune persons provides the diseases with an “opportunity,” if you will, to replicate throughout the population in the form of various epidemics.
Each epidemic, in turn, strikes hardest at those individuals least capable of defending themselves — the elderly, the newborn, the immuno-comprised, and, of course, pregnant women and their developing fetuses.
So the occurrence and recurrence of preventable diseases does not simply create a toll of individual suffering; there is also an incalculable toll on our public health system in the form of missed opportunities for disease eradication. Awful diseases like smallpox, polio, measles, and diphtheria have been eradicated or at least made exceedingly rare in the U.S. thanks to the public's cooperation with the standardized vaccination schedule.
Parents who are unconvinced by the reassurances of the medical community and remain concerned about getting their children vaccinated should note that thimerosal-reduced and thimerosal-free vaccines (search) began coming on the market in 1999 -- again, not because thimerosal is a proven risk, but to allay concerns over vaccine safety.
Many critics have argued, however, that traces of thimerosal (and/or mercury, one of its components) can still be found in many vaccines, so parents wishing to avoid such substances altogether should ask to see package inserts and discuss the issue with their health care provider.
But parents shouldn’t be discouraged from getting their children vaccinated. Vaccines can sometimes have side effects, some of them serious—although mainstream medical opinion holds that autism is not one of them—yet these side effects pale in comparison to a scenario of large-scale declining immunity and increasing epidemics in our society-at-large.