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The Secret Truth

Parents used to accept routine vaccinations for their children without a second thought. But as more parents weigh the benefits of vaccination against the possible risks, some are hesitating, even resisting, those shots, as doctors struggle to persuade them of their safety. At stake is the health of a nation.

Looking back, Marjorie Hansen suspected something was wrong when her toddler Jacob started repeatedly running into the street without warning. She never would have guessed that her family's world was about to change forever.

In 1999, Marjorie and her husband, Jared, lived in Utah, having married several years earlier while attending Brigham Young University. "We went to a lot of operas," recalls Marjorie about their dates. For several years after graduating, Jared worked as a research chemist - primarily on explosives - before returning to business school. A history and political science major, Marjorie stayed home to raise Jacob and his older sister, Brianne.

As an infant, Jacob had been very social, full of smiles and responsive cooing. But a few months after his first birthday, says Marjorie, he had a "Dr. Jekyll-Mr. Hyde transformation." He stopped making eye contact. He lost his ability to say several words and was eventually left with only one: "No." He would scream uncontrollably in front of cupboards while Marjorie frantically emptied them to find out what he wanted. Sometimes he didn't want anything. She couldn't console him. "We just thought we were bad parents," confesses Marjorie on a recent evening when I visited their home. Worried about her maternal skills, she even enrolled in a parenting class.

But the problems continued. In Utah, Jacob once ran out of the house, and Marjorie anxiously looked through her neighborhood, going door to door. She'd learned not to call his name, since that just made him run farther. She finally found him hiding near a neighbor's garage. The pediatricians weren't helpful, she says, since "they didn't call it anything. They always said, 'Don't worry, just wait.' " After nine months, Jacob finally received speech therapy, but without any formal diagnosis. In early 2000, Jared took a job in Framingham. Shortly after the move to Massachusetts, a new team of doctors diagnosed Jacob. Marjorie remembers: "That's the first time we heard the word 'autism.'"

By then the Hansens had a third child, William, who was developing normally. "You could read five books and he would sit and listen," says Marjorie. Then, in late 2001, William suddenly stopped making eye contact. Horrified, the Hansens watched him also lose his words and sociability. "I mean it was scary. Cognitively, he regressed to a 9-month-old," said Marjorie. Just shy of 2, William also was diagnosed with autism.

On the Internet, Jared read about a possible connection between autism and a mercury-based vaccine preservative called thimerosal. Marjorie recalls: "One day I decided to look up their vaccination records. And I found out that both of them had had routine vaccinations two weeks before [the symptoms began]. And I became convinced that the vaccination is what, you know, the final straw - the trigger in the susceptible individual." Today, she says, she is "100 percent certain" that vaccines caused the autism.

How an unlikely theory pushed the Hansens - and others - to reject many routine childhood vaccinations dramatizes the biggest dilemma in public health today. Most diseases prevented by vaccines, like polio, measles, and whooping cough, are now pretty uncommon, and many people like the Hansens believe the benefits of vaccines don't outweigh the risks. To increase public acceptance of vaccines, then, should health authorities spin the facts to make the diseases seem deadlier and the shots seem safer? The surprising thing is that they already do. And whether we like it or not, it may be better that way.

VACCINES HAVE LONG AROUSED resistance and suspicion. In 1901, an epidemic of 1,600 smallpox cases broke out in Boston, and the Board of Health required that all residents get vaccinated or face a fine or jail sentence. Almost half a million Bostonians were vaccinated, some forcibly. Protests led to a 1905 US Supreme Court case, Jacobson v. Massachusetts. The court ruled in favor of the state, establishing the precedent for 100 years of public health law.

Today, American toddlers receive roughly 15 separate shots against a dozen diseases before they are 2 years old. Because the shots aren't perfect, most require repeated doses; for example, children get four shots for tetanus and three for polio over two years. Under certain conditions, a 15-month-old can get as many as half a dozen shots at a single doctor's visit.

Perhaps because of the near-universal administration of vaccines, there have been numerous, ultimately unsubstantiated, claims linking vaccines with various diseases, including the diphtheria-tetanus-pertussis vaccine with epilepsy and Sudden Infant Death Syndrome (SIDS), the hepatitis B vaccine with SIDS and multiple sclerosis, the Lyme vaccine with arthritis, the Haemophilus influenza vaccine with diabetes, and many others. Of course, there are some proven vaccine-related injuries, mostly acute allergic reactions. In 1986, before the thimerosal-autism debate began, the National Vaccine Injury Compensation Program was created to protect vaccine makers, and thus the nation's vaccine supply, from costly litigation by people who were adversely affected by vaccinations. Since its inception, the program has paid more than $1.5 billion on about 1,900 claims.

Fundamentally, the proposed connection between autism and thimerosal arises from the frustrating lack of known causes for autism and Autism Spectrum Disorders. The theory joins others blaming various exposures for baffling diseases; consider discarded notions correlating cellphones with brain tumors, silicone breast implants with autoimmune disorders, and water fluoridation with bone cancer. But because of its history, the link between vaccination and autism has acquired unusual traction.

AUTISM FRIGHTENS PARENTS more than almost any disorder, since it implies that the child can never function independently in society and may never fully reciprocate, or ever fully appreciate, expressions of love. Classically, the condition consists of three problems: lack of social interaction skills or empathy, disordered or delayed communication (such as speech), and impaired play or imagination. Though portrayed in the public imagination by characters such as Dustin Hoffman in Rain Man, autistic people are like snowflakes: No two are alike, and the clinical spectrum ranges from severe disability to near normalcy.

The vaccine-autism saga begins with a humanitarian relief mission in Iraq. In the fall of 1971, a famine broke out in Iraq, and thousands of tons of wheat seed were distributed in rural communities. The seeds were treated with methyl mercury, a fungicide similar to the preservative thimerosal, and though farmers were supposed to plant the seed to grow crops, many mistakenly ground the wheat and baked bread. Of the estimated 50,000 people eating the treated wheat, 6,500 were hospitalized for mercury poisoning, and hundreds died. Many pregnant women who survived gave birth to children with mental retardation and other birth defects.

Hoping to learn from this horrific incident, the United States Environmental Protection Agency studied blood and hair samples from the Iraqis, and, with many assumptions, calculated a "safe" level of mercury exposure - then divided that allowable amount by an "uncertainty factor" of 10 to come up with the limits we use today. (Some toxicology data from Japan and the Faroe Islands were also used.) In 1999, Drs. Leslie and Robert Ball at the Food and Drug Administration realized while looking at vaccine safety that, under certain conditions, infants getting multiple vaccines containing mercury-based thimerosal exceeded the EPA's cumulative mercury limit, up to threefold. (Of note, the cumulative doses did not exceed the less-strict limits set by the World Health Organization or the FDA.)

This finding came at a bad time for vaccines. A year earlier - in an event unrelated to thimerosal per se -the British medical journal The Lancet published a study suggesting that the measles-mumps-rubella (MMR) vaccine may have caused bowel problems and autism in 12 children. In a press conference, the lead author, Dr. Andrew Wakefield, then warned the vaccination should be "suspended." Shortly afterward, Prime Minister Tony Blair refused to answer questions about whether his youngest child had received the vaccine, and MMR vaccination rates began falling across Britain. Last year, Wakefield's coauthors retracted the paper, since Wakefield hadn't disclosed that most of the children were involved in lawsuits against vaccine makers. And last month, investigative journalist Brian Deer alleged in The Sunday Times of London that Wakefield hoped to profit from the panic he created, having filed to patent his own "safer" vaccine product.

Multiple studies have now convincingly refuted Wakefield's suggestion that the MMR vaccine causes autism. In 1999, though, just after the Lancet article was published, the stage was set for the autism-thimerosal link. It was then that Dr. Thomas Verstraeten, a Centers for Disease Control and Prevention epidemiologist who now works for the vaccine maker Glaxo SmithKline, produced conflicting data suggesting a possible link between thimerosal and speech delay (though the final version of his paper, published in 2003, concluded that "no consistent significant associations were found" but encouraged future study; a more complete CDC study of thimerosal will finish in 2006).

Ironically, Dr. Neal Halsey - a leading vaccine specialist based at Baltimore's Johns Hopkins who pushed to eliminate thimerosal from vaccines immediately after the FDA analysis by the Balls - believed that a quick response would enhance public trust in vaccine safety. After all, federal authorities called for the removal of thimerosal from vaccines in 1999 as a precautionary measure, without conclusive proof of harm, and some states, including Massachusetts, stopped administering childhood vaccines containing the preservative as soon as alternatives became available.

Instead, the fear of thimerosal - amplified by Wakefield's unrelated, misleading work on the MMR vaccine - continued to grow. In fiscal 2003, the National Vaccine Injury Compensation Program received 2,438 claims alleging that vaccines had caused autism, up from 18 claims in 2001. After his grandson was diagnosed with autism, Rep. Dan Burton, an Indiana Republican, called congressional hearings to investigate a link. This year, New York Times contributor David Kirby published Evidence of Harm, a sympathetic portrayal of the parents who blame vaccines for their children's autism; Robert F. Kennedy Jr. wrote an article for Rolling Stone and suggesting a conspiracy to cover up a thimerosalautism connection (and later was forced to write several clarifications and corrections). Many parents continue to be concerned.

It's now hard to overstate the scientific evidence against the thimerosal-autism link. Many, many chemicals seem dangerous in test tubes or in animal studies but have no significance in the real world; thus, the most useful safety data come from large-scale "epidemiological" studies of people. In 2004, the prestigious Institute of Medicine, the federal government's adviser on public health, reviewed dozens of such studies related to vaccines and autism and concluded the "evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism." Halsey sees this as a powerful statement, since "that's about as strong as the IOM will come out." In contrast to many massive studies from major academic centers that found no link, the only epidemiological studies favoring a link were one unpublished study from Mark Blaxill, a Massachusetts-based consultant and board member of an advocacy group called SafeMinds, and five separate published studies from the home-based father-son team of Dr. Mark Geier and David Geier - and these were all dismissed by the IOM as "uninformative" or "uninterpretable" due to poor methods.

As far as mainstream scientists are concerned, the vaccine-autism question is settled.

What the movement to blame thimerosal for autism shows is a secret of the public health authorities. Stated baldly, they blatantly exaggerate some risks and minimize others, since for any individual, the consequences of most unhealthy behaviors are minimal and there is little incentive to change. (After all, for example, more than 95 percent of cigarette smokers never get lung cancer.) But what happens when two well-intentioned parties armed with scientific data - that is, advocates wanting to prevent autism and health authorities wanting to ensure widespread vaccination - collide? Who, in the end, is right?

"I WAS ALWAYS VERY PRO-VACCINE. I thought that parents who didn't vaccinate were negligent," Marjorie Hansen says. After learning about thimerosal, she and Jared changed their minds. Jared was "incensed" by the presence of thimerosal in childhood vaccines, recalling that as a student, he handled mercury with the same care reserved for radioactive materials. Convinced that public health authorities already took unacceptable risks with their children, they no longer accept their pediatrician's routine vaccine recommendations without questions. They also have filed a claim with the National Vaccine Injury Compensation Program.

In particular, Marjorie and Jared believe that vaccination during early infancy, such as for hepatitis B, presents an unacceptable risk-benefit ratio for their children. In addition to their sons' conditions, each has several relatives who have developed seizures, high fevers, or other problems following vaccination, and the Hansens worry that their family's "genes" don't tolerate vaccines well. To them, the benefits of many vaccines seem far-fetched. According to the CDC, the sources of infection for most cases of hepatitis B are intravenous drug use, sexual contact with infected persons, or being born to an infected mother. Since their children lack these risk factors, wonder the Hansens, why should they be vaccinated at birth?

The Hansens applied similar calculus to other vaccines. Inoculations that didn't make the risk-benefit cut were shots against chicken pox, flu, and a bacterial infection called pneumococcus. Those diseases, they said, were rarely deadly and the risks of vaccination were too great. They did allow their youngest girl (both daughters are developmentally normal) to be vaccinated against polio, diphtheria-pertussis-tetanus, and MMR - the last only "when her immune system was fully developed," though most authorities strongly advise against selective vaccination.

THE BREAKDOWN OF TRUST triggered by the health authorities' acceptance of thimerosal in vaccines seemed to carry into other established medical arenas. Because, in their opinion, the regular doctors offered few useful treatments for their sons, Marjorie and Jared began experimenting with therapies outside the mainstream.

Many autistic children also experience gastro-intestinal problems, so the Hansens had William tested for food allergies. These tests were positive for sensitivities to gluten (a component of wheat and other grains) and casein (a milk protein). At considerable expense and inconvenience, the Hansens eliminated wheat and dairy products from both boys' diets. They reported tremendous improvement, and each child seemed less "hyperactive." From being "skinny unhealthy," the boys seemed to bulk up. Jacob, who was already acquiring some language and social skills in his 10 hours per week of speech and behavior therapy, seemed to improve dramatically, Marjorie says, "He wouldn't be diagnosed" with autism now, she says.

The Hansens also administered large doses of vitamin B6, vitamin B12, and, after one practitioner ordered tests and concluded that one of the boys was a "zinc waster," zinc supplements. They also tried a drug called glutathione, a natural detoxifying compound normally found in the liver. But their most quantitative experiment concerned chelation.

Derived from the Greek "chele," or claw, chelation therapy uses pincerlike molecules to bind to and remove heavy metals like iron and lead from the body. Used rarely for acute lead poisoning, chelation has been adopted by numerous alternative practitioners to treat supposed lead or mercury poisoning. It has been promoted as a cure-all by books like Dr. Hal Huggins's It's All in Your Head (blaming mercury-based dental fillings for many conditions) and Dr. Morton Walker's Everything You Should Know About Chelation: Unclog Your Arteries and Rejuvenate Your Cardiovascular System Without Surgery and Other Invasive Procedures.

Suspicious of any therapy lacking a "rational basis," Jared figured chelation was worth a try, given William's exposure to thimerosal and another practitioner's assertion that his son's urine had abnormal amounts of mercury. In particular, the Hansens hoped chelation would improve William's toileting behavior (many children who are diagnosed with autism also have problems toilet training). Jared realized chelation was a long shot, saying, "What helps in one child may not help in another. It's all trial and error." (Still, no peer-reviewed study has ever shown that chelation helps anything other than acute lead poisoning, and could even be dangerous. In August, a 5-year-old autistic boy, Abubakar Nadama, died in Pennsylvania of cardiac arrest following a third round of chelation therapy from an alternative practitioner.)

After beginning chelation, Marjorie decided to keep track of William's toileting behavior and painstakingly plotted these points on lined and labeled sheets. Satisfied with the outcome, she flipped through sheet after sheet of graph paper for me and said she felt that her data showed a correlation between improved toileting over several weeks and the chelation treatments.

In this manner, the Hansens performed their own clinical trials with a study population of two, or sometimes one. They made hypotheses and drew conclusions about the role of thimerosal in causing autism, the benefits of elimination diets, mercury chelation therapy, and various vitamins. They applied the techniques of science, quantifying the results and even graphing them carefully over months. They acted on the results, rejecting some treatments as useless, like vitamin B12 therapy, and embracing others as beneficial, like chelation and eliminations diets.

On some level, the Hansens' methods are understandable, since there are no larger clinical trials involving, for example, elimination diets and vitamins. Before the 20th century, all medical research resembled the Hansens' experiments. But in spite of their intuitive appeal, personal anecdotes are also a crucible of quackery. Even hundreds of them don't add up to reliable data. The Hansens thus committed an ancient error by using their personal experience to link vaccines with their sons' autism. They transmuted a likely coincidence into truth.

LAST YEAR, MIT PROFESSOR Josh Tenenbaum told Psychology Today: "Coincidences drive so many of the inferences our minds make. Our neural circuitry is set up to notice these anomalies and use them to drive new learning. There is an old saying that neurons that fire together wire together. So you could say that coincidence operates at the level of the synapse, whenever neurons fire at the same time."

This "neural circuitry" explains why some parents believe the rise in autism over the past years has been linked to the higher number of childhood vaccines. (The same circuitry could also relate the increasing use of cellphones, popularity of reality television, or consumption of fast food to autism.) Consider that almost 90 percent of children receive vaccines at 15 months of age, the same time that many cases of autism are diagnosed. Inevitably, many autistic children will be diagnosed immediately after receiving vaccines - and, like the Hansens, parents will suspect a causal connection.

Once scientists have a suspicion about what causes a disease, they design experiments to prove or disprove their theory. Philosopher Karl Popper wrote that the defining characteristic of a scientific theory is "falsifiability." In other words, you must clearly define what could make you change your mind. This is the problem with some proponents of the vaccine-autism theory: No amount of data can falsify their belief.

Consider some letters to The New England Journal of Medicine following a 2002 study of 500,000 children debunking the MMR and autism link proposed by Wakefield. No statistically higher risk of autism was present in vaccinated children compared with unvaccinated children. Yet, some letter writers were upset the studies didn't address the possibility that, as one physician wrote, "there is a vulnerability to MMR-induced disease in 10 percent of the children with autism." In other words, the writer accepts that vaccines don't have a big impact on autism. But, he asks, couldn't there be a few kids who had an unusual sensitivity to vaccination?

The study authors answered: "We cannot rule out the possibility that at least one child would not have become autistic if he or she had not been vaccinated, and that point alone may be sufficient for stating causality. Unfortunately, we cannot subject this assumption to a critical test unless it is better specified." Thus, they may have studied half a million kids, but there are millions of others out there, and one of them might be different. No amount of data can refute that possibility.

What this means is that no clinical trial, no matter how well-funded or well-designed, can ever prove a negative - it can only show that a possible cause-effect association is very, very unlikely. That is why it will always be impossible to eliminate the perceived link between thimerosal and autism.

THE PUBLICITY SURROUNDING the vaccine-autism hypothesis almost derailed vaccination in America. It relied on the all-too-human tendency to make erroneous causal connections. And it also exposed how tenuous the acceptance of vaccination can be, once parents start balancing risk and benefit on their own.

Today, the medical culture of developed countries relies fundamentally on "informed consent," where patients review the pros and cons of all treatments and can refuse for any reason. So public health agencies try scaring parents into vaccinating, even though actual risks of any one child today getting polio or pertussis are extremely low.

On its website, the Massachusetts Department of Public Health reports, "In 1 out of 4 men, mumps causes swollen testicles." Promoting pertussis (whooping cough) vaccine, the Centers for Disease Control explains, "In infants, [pertussis] can also cause pneumonia and lead to brain damage, seizures, and mental retardation." Chicken pox, the CDC reports, "can lead to severe skin infection, scars, pneumonia, brain damage, or death."

While public health authorities hype the benefits of immunization, parents try to determine if the risks of side effects, even highly unlikely ones, are worth it. And the presence of a convincing group of people who believe that vaccines can cause autism - like the Hansens - scares parents about vaccines.

If given the choice, many parents vote with their feet. In Britain, for example, vaccination is optional, and MMR immunization rates fell to 80 percent overall after the Wakefield report, and 62 percent in parts of London. According to the journal Science, measles began to spread twice as efficiently as before. In 1987, Japan allowed parents to decide whether their children should be vaccinated against several diseases, including measles. Many opted out, and now more than 100,000 cases of measles occur each year, with an estimated 50 to 100 deaths.

The secret truth about vaccines is that they don't have much of a benefit for the individual child who receives them. They're mostly for the good of the community. My sons got multiple polio shots, for example, for little personal benefit. The same goes for flu, measles, whooping cough, chicken pox, and almost every other immunization. The reason they'd be fine without the shots is that most everybody else gets them. This concept is called "herd immunity," and it is the foundation for disease control. Essentially, it means that once a critical "tipping point" for vaccination coverage occurs - say, about 90 percent of the population - the probability of getting a disease suddenly falls, since it can't spread.

Following a 1957 influenza pandemic, the Japanese government began vaccinating all schoolchildren, since they spread flu efficiently. After mandatory vaccination ceased in 1994, a report in The New England Journal of Medicine found that the vaccination campaign had prevented as many as 49,000 deaths annually among the Japanese population. That is, one older person's life was saved for every 420 children vaccinated.

In the United States, getting your kids vaccinated is like paying your taxes: Cheating a little doesn't really hurt anyone as long as everyone else pays up. But left to their own devices, parents may balk at subjecting their children to the needle when there's no significant risk of disease. So the United States decided in the favor of greater good and not individual rights, making certain vaccinations compulsory for admission to public schools and day-care centers. As a result, despite well-publicized small outbreaks of whooping cough and even polio recently, vaccination rates in the United States are higher than ever. Today, about 90 percent of Massachusetts children and 80 percent nationwide are fully immunized - and millions of people enjoy some of the world's lowest rates of devastating but preventable infections.

THE HANSENS ARE LOVING, devoted parents. When we spoke in their dining room a few weeks ago, Jacob poured me a glass of lemonade and popped into the room repeatedly to make contact by smiling. When their daughter spilled milk in the kitchen, Marjorie patiently cleaned it up and reasoned with her about being more careful. They brought the same consideration to our conversation, knowing that I was probably skeptical of their theory.

I now better understand how the Hansens came to believe that vaccines cause autism, even though I still do not share their belief.

Like the Hansens, many of us have a hard time being truly scientific and objective when our loved ones are involved. It's terribly hard to accept that the universe operates in random ways and that innocents may be harmed. What we choose to do with that sorrow is not always rational. We seek explanations, no matter how unlikely they may be. And who knows: If my sons were autistic, perhaps I, too, would have believed that something, maybe even vaccines, could have caused it.

The Hansens, like most people, want the best health for children. "Vaccines are one of the great successes of medicine," Jared says. He doesn't want to stop vaccination, but rather allow parents to weigh the pros and cons. When I explain that leaving the choice to parents can harm herd immunity, as in Japan and Britain, he expresses genuine concern. "That's a very good point," he says.

Perhaps that is why it's better that our public health policies require childhood vaccination and discourage individuals from making the choice themselves. In the final analysis, the secret truth about vaccines may be that, sometimes, personal freedom can be a dangerous thing.

Dr. Darshak Sanghavi, an assistant professor of pediatric cardiology at the University of Massachusetts Medical School, is a Globe columnist and the author of A Map of the Child: A Pediatrician's Tour of the Body. E-mail him at 

Copyright 2005 The New York Times Company