Nancy A. Melville

June 04, 2012

June 4, 2012 (Thessaloniki, Greece) — The unsettling reemergence of diseases previously eradicated by vaccines in some countries underscores the challenges clinicians face in driving home the importance of vaccines in a manner that resonates with parents, said Gary S. Marshall, MD, here at the European Society for Paediatric Infectious Diseases 30th Annual Meeting.

Outbreaks have been well documented, ranging from pertussis and measles in California to major measles epidemics in the United Kingdom and Europe. The cause of these outbreaks is no mystery.

"These are places where measles was eliminated in the 1990s; there's only one reason why it has returned — parents are afraid of vaccinating their kids," said Dr. Marshall, who is a pediatric infectious disease specialist at the University of Louisville in Kentucky.

"The shift in the paradigm in the past few decades has been from fearing the diseases to fearing the vaccines that prevent the diseases in an environment where the diseases aren't occurring anymore."

Clinicians are under pressure to better inform patients. To address the hesitancy related to vaccination, it is important to understand the underlying cultural and even evolutionary factors that explain it, Dr. Marshall explained.

Although fear of vaccines dates back practically to their origin, much of the blame for modern-day fears lies in discredited research linking the measles, mumps, and rubella (MMR) vaccine to autism.

That research was deemed by the medical community to be an elaborate fraud. Its author, Andrew Wakefield, was barred from practicing medicine in the United Kingdom, but not before the seeds of distrust in vaccines were firmly planted into the public consciousness.

Antivaccine celebrities and activists took to the airwaves and the Internet with harrowing anecdotes of febrile seizures and autism disorders allegedly linked to the vaccine; the dry evidence-based science was drowned out by the noise.

The medium "has not been the only message," however. According to Dr. Marshall, parents' seemingly irrational beliefs that they are protecting their children by not having them vaccinated can be a more deep-seated survival instinct.

He described the evolutionary safety net of the false positive — "a caveman on a picnic hears a rustle in the grass; he fears it is a predator, packs his things, and goes home. In fact, it's just the wind — but there are no consequences. The caveman survives."

The caveman who commits a false negative, however — thinking it is just the wind when in fact it is a tiger — faces nothing less than elimination from the gene pool.

"Over time, we have evolved to become creatures that commit type 1 (false-positive) errors," Dr. Marshall said. "We reject the null hypothesis that vaccines don't cause autism, when in fact the null hypothesis is true."

Reaching Parents Requires Dropping the Scientific Jargon

In addition, there is the more recent cultural conditioning — particularly in the United States; many people are simply not taught to evaluate information scientifically, resulting in an easy misinterpretation of statistics, patterns, and risk.

Clinicians need to clarify a message that parents can accept and comprehend, Dr. Marshall said.

"We have difficulty...breaking down the barrier between scientific communication and talking to parents," he explained.

"We need to think about the language we use to communicate just how well the system works in picking up even rare adverse events and protecting children from them."

He emphasized the need to encourage parents to perceive information with deductive reasoning, to consider risks along with benefits, and to "change anecdotal thinking into scientific thinking."

However, considering the tone of the antivaccine messages, it might not hurt for clinicians to resort to a few heavy-handed anecdotes of their own, Dr. Marshall said.

"In some ways, we physicians are socialized to be so professional; we stick to the data and we don't fight fire with fire," he said.

"With some parents, it may just be a matter of counterbalancing the anecdote of the allegedly vaccine-injured child with the anecdote of the child who spent his life in an iron lung, or the one who died from measles because he wasn't vaccinated."

Evidence of Widespread Disease: The Antidote to Anecdote

The incidence rates of measles in the United States in the prevaccination era speak for themselves, providing a powerful illustration of widespread disease that is far from anecdotal, according to James D. Cherry, MD, MSc, professor of pediatrics at the David Geffen School of Medicine at the University of California at Los Angeles and Mattel Children's Hospital.

"In the last epidemic in the United States, from 1989 to 1991, before we had the vaccine in this country, there were 55,000 cases of measles and 123 deaths, including 17,000 cases in California and 70 deaths," said Dr. Cherry.

He noted that for parents who believe that the risk related to the measles vaccine is greater than the risk associated with the disease itself, some statistics can be useful.

"For every measles-related death, there are 4 children who will get some degree of brain damage from encephalitis," he said. "In the prevaccine era (1950s), there were as many as 500 deaths and 1000 cases of encephalitis each year in the United States, and many of the encephalitis cases had residual brain damage."

Dr. Marshall and Dr. Cherry have disclosed no relevant financial relationships.

European Society for Paediatric Infectious Diseases (ESPID) 30th Annual Meeting. Presented May 10, 2012.

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