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PUBLIC HEALTH

Vaccines Are Safe and Vital

Two Recent Incidents in Vaccine Policy Underscore Need for Effective Communication

young boy receiving a vaccine from a nurse SOURCE: AP/MARCIO JOSE SANCHEZ Last week, the British Sunday Times reported that the original study which sparked a ten-year debate about vaccine safety and autism was based on faulty data. Days later, a special U.S. court ruled that there is little to no evidence linking vaccines to autism. Together, the two events may cool a simmering debate about how to protect young children’s health.

“The superior doctor prevents sickness; the mediocre doctor attends to impending sickness; the inferior doctor treats actual sickness.”
—Chinese Proverbs

Last week, the British Sunday Times reported that the original study which sparked a ten-year debate about vaccine safety and autism was based on faulty data. Days later, a special U.S. court ruled that there is little to no evidence linking vaccines to autism. Together, the two events may cool a simmering debate about how to protect young children’s health.

Amid the controversy and polarizing discussion, it’s easy to lose track of why vaccination is so important. Concerns over a link between vaccines and autism have become commonplace among some members of the public and within the media itself. Mainstream outlets typically frame the issue as a raging debate, but the truth is that the science is straightforward and overwhelmingly weighted towards the benefits of vaccination.

The furor of the argument is understandable. When pitting the emotional fears and worries of a parent against the unfeeling rationality of cold, hard science, it is hard to know if the two sides are even speaking the same language. Further, it is difficult to keep track of the criticisms and theories, and to understand the foundation of objections to vaccination protocols. This article will shed light on the discussion, beginning with an overview of how vaccines work, and then focusing on some of the popular criticisms.

How vaccines work

All vaccines do essentially the same thing; they train the immune system to recognize foreign bodies. That way, when a person’s body is exposed to the real thing, it will have specific antibodies that recognize and inactivate the germs before they can infect (this is sometimes referred to as humoral immunity), while a type of white blood cells called memory T cells eliminate any infection that occurs (a process called cellular immunity). Vaccines build specific defenses to a single disease, but sometimes multiple vaccines can be combined into a single dose, as in the case of the MMR (measles, mumps, and rubella) or the DTaP vaccines (diphtheria, tetanus, and pertussis).

There are two principal types of vaccines: killed and live attenuated. Killed vaccines are precisely what you would guess: the virus or bacteria is killed and mixed with chemicals designed to activate the immune system.  The entire germ or unique subunits can be used. Once the vaccine is administered, the immune system is able to pick up these unique identifiers of the pathogen and establish some memory of it. The second strategy is to expose the body to an attenuated infection, or to a related non-pathogenic strain. This has the added benefit of building much stronger immunity, but in some cases there is a risk of actual infection, particularly in patients with weakened immune systems.

Beyond protecting the individual, vaccines are broadly administered in order to establish what is referred to as “herd immunity.” Most infectious diseases require a ready supply of healthy hosts in order to continue spreading. So, if enough people get vaccinated, entire illnesses can go from serious public health threats to occasional isolated incidents. This way the young, the elderly, the sick, and even those who are unsuccessfully vaccinated are protected by the majority. Vaccination rates necessary to establish herd immunity vary by the pathogen, but they can be as high as 95 percent—very little room is left for those who voluntarily choose not to get vaccinated, which is why mandatory vaccinations are widely instituted.

To be clear, there is no such thing as a perfectly safe vaccine. Like any other medical treatment, there are side effects and risks involved. In rare cases, live attenuated vaccines could induce the illness they protect against, which could even be spread to those who are not vaccinated. Most of the known risks are rare and relatively minor—most people are familiar with the redness and swelling following a flu shot—and the benefits of vaccination far outweigh them. There currently exists no evidence that autism is a potential risk factor for vaccination, but a 1998 study speculated that there was a potential link, triggering a small but vocal anti-vaccine movement.

Andrew Wakefield and The Lancet Report

The origins of the controversy linking vaccination and developmental disorders dates to a clinical report published in the British medical journal The Lancet in 1998, although the first mention of the hypothesis dates back at least two years earlier. A group of British gastroenterologists led by Dr. Andrew Wakefield were interested in the association between autism spectrum disorders, or ASD, and colitis, a form of intestinal dysfunction. While this was a clinical report conducted by trained medical professionals, it is important to keep in mind that this was an observational report—no experiments were performed. The authors reported on 12 children (ages three to ten years, predominantly boys) with these symptoms. It was noted that eight of these children had received the live-attenuated MMR vaccine within two weeks of the onset of symptoms. In the discussion section of the paper the authors postulated that because viral encephalitis can give rise to autistic disorders, and that in some cases measles has been associated with some forms of colitis, it could be possible for the vaccine to lead to a full viral infection that was to blame for both the autism and the colitis. The authors emphasized that they were unable to show any causal association, but they did say that further virological studies were underway to resolve the question. No such study demonstrating a link was ever released.

Following the publication, Wakefield, the primary author of the report, held a press conference at which he deemed potential link between MMR and autism dangerous enough to suggest altering the vaccine schedule, despite not having done any research so support his claims. The controversy was widely reported by the media, leading to widespread doubts about the safety of vaccination. British vaccination rates fell from 92 to 79 percent, and in certain urban areas rates fell even lower—well below levels necessary to maintain herd immunity.

In February, 2004, a story by Brian Deer appeared in the Sunday Times which turned the public eye back towards Wakefield. It revealed that not only did Wakefield have a history of attacking the use of the MMR vaccine prior to conducting any relevant research, but he had also obtained £55,000 in research funding from a legal fund representing some of the children in the Lancet study. This funding was specifically intended to investigate the potential link between the vaccine and autism, and several of the participants of the study were actual litigants with a significant interest in revealing such a link. Although the doctors conducting the clinical exams were ignorant of the legal action, no conflicts of interest were reported to the journal. Deer quoted an editor of The Lancet as saying that had the journal known of these conflicts of interest, it would not have published the controversial study.

Six years after the original publication and less than a month following the Sunday Times piece, ten of the twelve authors on the study published a “Retraction of an Interpretation,” and reemphasized that they did not discover any causal links between autism spectrum disorders and vaccines. Wakefield responded by defending the original findings as published, rejecting any impropriety on his behalf, and argued that the vaccine should not be ruled out as a potential cause of ASD.

On February 8 of this year, almost exactly five years after his original Sunday Times story, Brian Deer wrote a follow up to the MMR-Autism study. It revealed that the published Lancet accounts for most of the original 12 children were falsified. The data in the study did not account with the hospital records. Only one of the children’s symptoms began soon after vaccination, and in most cases behavioral symptoms had manifested before the child received any vaccination.

The sum of these reports is that a gastroenterologist with a bias against vaccination recruited a series of autistic children whose parents blamed the vaccine for their condition. He was then paid to research these claims. Without any solid evidence he falsified a weak link, and began using the media to spread dire warnings based on a weakly formulated hypothesis. As a direct result of this, thousands of children have contracted preventable diseases, and a few have even died.

Thimerosal, another source of controversy

Following the Wakefield study, concerns arose that any link between autism and vaccination may be caused by the preservative thimerosal. Notably, thimerosal was not present in the British formulation of the MMR vaccine, and not relevant to the Wakefield hypothesis. Thimerosal is a mercury-containing compound that was long used a preservative for a range of vaccines. Like any preservative, thimerosal served to keep any bacteria or fungi from growing in vaccine preparations. Prior to its introduction, sepsis was a significant risk in vaccinated individuals, particularly from multi-dose vials of vaccine. In one case, prior to the widespread adoption of thimerosal, 12 of 21 children vaccinated from a staphylococci-contaminated vial died in Australia.

Concerns over the potential toxicity of thimerosal—as opposed to the toxic effects of elemental mercury—which are well established—came to the fore in 2001 following the publication of a literature review by Sallie Bernard, et al, in Medical Hypotheses, a journal known for publishing radical ideas. The article did not present any new data, but reviewed existing publications in order to build its argument. The main hypothesis again relied on parental reports of behavioral changes occurring following immunization schedules, including that of Bernard herself. It went further by detailing the similarity of neurological symptoms following mercury poisoning and ASD. Also, in order to accommodate the strong genetic linkage in autism spectrum disorders, the authors postulated that a genetic susceptibility to the effects of mercury in some people could lead to ASD.

In 1999, prior to the publication of the Bernard, et al. paper on thimerosol, the Food and Drug Administration conducted a study to determine whether the metabolites of thimerosal were safe. Allergic reactions were described—redness and swelling at the injection site. They were typically mild and only lasted a few days. In some isolated cases mercury poisoning has been demonstrated with thimerosal, but never in the context of a vaccination; in one case a child’s ears were directly irrigated with thimerosal. Toxic doses were on the order of 1,000 to 10,000 times the concentration of ethylmercury found on a routine vaccination schedule. Additional safety concerns were raised regarding the ability of infants to clear mercury compounds. Blood samples were analyzed from infants receiving routine vaccinations, and they were all found to be within reasonable safety limits

Despite the lack of evidence of toxicity at vaccination levels, as an extra precautionary measure, the FDA, the National Institutes of Health, the Centers for Disease Control, and the Health Resources and Services Administration urged vaccine manufacturers to reduce or eliminate thimerosal from their vaccine preparations. Today, the only vaccines recommended for children containing thimerosal are the inactivated flu vaccine (the shot, not the mist), and some DTaP preparations. Further, following the removal of thimerosal from the vast majority of vaccines, there has been no discernible decrease in the rate of autism—a mixed blessing for defenders of vaccination.

In 2001, the Institute of Medicine convened a board specifically to investigate the hypothesis raised by the Bernard paper. They did not find sufficient evidence to either reject or accept the hypothesis that thimerosal exposure was linked with any neurodevelopmental disorders. In 2004, the board reconvened to take into account the overwhelming new evidence, and rejected the causal relationship between thimerosal and autism. They also emphasized that vaccines were proven prophylactic agents, and that decreased vaccination rates imposed serious risks to public health.

Legal questions

Concerns over thimerosal inevitably left the realm of scientific discussion and public health policy, and entered the legal world. The United States actually has a special court to hear vaccine related injury cases. Following an earlier DPaT vaccine scare in 1988 (unrelated to autism), several lawsuits against vaccine manufacturers forced companies to cease production of DPaT out of fear of litigation. Congress responded by passing the National Childhood Vaccine Injury Act, directing the department of Health and Human Services set up the national Vaccine Injury Compensation Program, or VICP. The program provided an alternative to medical malpractice litigation, created the special vaccine court, and set a lower standard of proof for links to the injury. If a consensus of the board deemed an adverse reaction medically plausible and if it occurred soon after vaccination, then litigants were awarded compensation for medical expenses and pain and suffering. No causative link between the injury and vaccine was necessary, including arguments that directly contradicted scientific evidence. In one extreme case, a litigant successfully argued that a hepatitis B vaccine had caused multiple sclerosis, despite a preponderance of scientific evidence to the contrary

The court rewarded compensation for nearly half of all claims, sending confusing signals regarding the presumed safety of vaccines. Since 2001 more than 5,000 families have filed claims with the court claiming a link between autism and the MMR vaccine. The majority of claims regarding autism were aggregated into a set of proceedings for which hearings did not begin until 2007. One exception was the case of Hannah Poling, a girl who developed autism-like symptoms after receiving a series of vaccines. The child had a rare mitochondrial disorder which predisposed her to similar neurological conditions, but the court awarded her damages despite the lack of evidence that the vaccines in any way exacerbated her condition. Many concerned parents saw this as a confirmation that vaccines do indeed cause autism.

Just last week, the VCID made the first of several rulings for the Omnibus Autism Proceedings. It found that there was no link between vaccination and development of ASD. In a further blow to the litigants, according to one New York Times article, the court declared evidence for the link “weak, contradictory, and unpersuasive,” and that “the petitioners in this litigation have been the victims of bad science conducted to support litigation rather than advance medical and scientific understanding.” Further rulings are still pending regarding the safety of thimerosal and other related claims.

Policy considerations

The science is indisputable: There is no definitive link between autism spectrum disorders and vaccination. It now seems that legal opinion is falling in line with the science, but the greater concern is the need for broader public understanding. No matter what is published in academic journals or decided in specialized courts, in order to rectify public confidence in vaccination, there must be outreach from the scientific community. It is important to ease frustration among concerned parents, as well as to communicate the importance of herd immunity. Scary rumors and whispered implications will always trump the cold hard facts of negative data—but that is only further reason to encourage scientific mindedness. We are living in an age where entire generations of families have grown up without any exposure to many of the diseases we vaccinate against. It is easy to focus on the fear of perceived risks when the known threats of not vaccinating are unfamiliar, and mitigated by the vaccination of others. It is a standard “tragedy of the commons” scenario.

There is no doubt that there exist plausible theories that could account for links to autism, or any other unknown risk factors associated with vaccination. Those hypotheses should not be discarded, but should be researched and explored. As a scientific community, we should not become reactionary and discard viable avenues of research because of potential political fallout. But it should be emphatically and directly stated that hypotheses without firm supporting data, and hypotheses with overwhelming counterfactual data should not trump reasoned public health policy.

The long and short of it is simple. There has been no credible link formed between autism and vaccination. Hypotheses have been generated, questions have been asked, and confusion has dominated. The true risk factor is the lack of effective communication between scientists and the public.

Mike Pazos is a Ph.D. candidate in the Department of Microbiology and the Mount Sinai School of Medicine Graduate School of Biological Sciences.

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