Vaccine Safety

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" Before vaccines, Americans could expect that every year measles would infect four million children and kill 3,000; diphtheria would kill 15,000 people, mostly teenagers; rubella (German measles) would cause 20,000 babies to be born blind, deaf, or mentally retarded; pertussis would kill 8,000 children, most of whom were less than one year old; and polio would paralyze 15,000 children and kill 1,000. Because of vaccines all of these diseases have been completely or virtually eliminated from the United States. Smallpox -- a disease estimated to have killed 500 million people -- was eradicated from the face of the earth by vaccines. And we're not finished; vaccines stand as our only chance to prevent pandemic influenza, AIDS, and bioterror, and our best chance to prevent certain cancers. "    

Paul A. Offit

Vaccines, Science and Denial

Few other public health initiatives (such as indoor plumbing) have done more good for our population than vaccines.

The routine vaccination schedule is based on years of research across the world.  Safety is always a top priority in this research.   As a result of this research, many of yesterday’s terrible diseases have become very rare.  Immunizations have saved billions of lives around the world. Modern culture feels no need to fear the devastating effects of infections such as measles, rubella, whooping cough, Haemophilus meningitis, tetanus, or polio. Vaccines have been so successful that we have forgotten what these horrors look like. These (deadly) infections still exist.  In fact, there have been resurgences of preventable illnesses due to anti-vaccine propaganda. As an example, in 2011, the W.H.O. reported over 30,000 cases of measles in Europe, mainly stemming a dramatic decline in vaccination. Of these cases, there were 27 cases of encephalitis and 8 deaths. This trend has spread to the United States due to international travel. In 2011, the C.D.C. reported 220 cases (nearly a quadrupling of usual cases). 

As with most successful scientific endeavors, there are denialists.  We encourage criticism of ideas. That is how we sort out good science from bad science.  However, critics must understand the subject.  They must accept good evidence when it is presented.  Good scientists accept evidence if obtained properly.  Good scientists communicate their findings in peer reviewed  journals.  Good scientists modify their ideas when new evidence becomes available. Bad scientists ignore good evidence. Bad scientists cling to debunked ideas. Bad scientists ignore the peer review process and run straight to the lay media with their unjustified claims.  This is called “pseudoscience”.

 In recent years, the popular media has inundated us with the pseudoscientific claims of the anti-vaccination movement.  Their false premise is that vaccines cause more disease than they prevent.  Of course, there can be side-effects, but these are rare. Attempts to publicize the overwhelming body of evidence about the benefits/ safety of vaccines are downplayed.  They are pushed to the back section of a newspaper.  Real science does not seem to be as popular as fake science.

A lot of the anti-vaccine pseudoscience and propaganda started in England with Dr. Andrew Wakefield.  In the 1990’s, he wanted to show that the measles vaccine (MMR) caused Crohn’s disease (a chronic bowel condition). He was unable to find any link.  Then, a group of trial lawyers looking to sue pharmaceutical companies paid Dr. Wakefield handsomely to find a relationship between the MMR vaccine and Autism.  

More on Dr. Wakefield in a moment.

Autism, Correlation and Causation

Autism is a very difficult and emotionally consuming problem for many families. We wish only the best for those who are dealing with autism.  A tremendous amount of patience, understanding and determination are required for all caregivers. Many treatments have been proposed.  Some pseudo-scientific ‘treatments’ like chelation have been deadly.  So far, only education and behavior modification strategies have been consistently useful.

We now recognize Autism more readily than we used to. In the past, only the severe form was recognized. This may be referred to as “Classic Autism”. It is thought to occur in 1 out of every 500 children.  Now, we recognize a spectrum of subtle forms, such as “Asperger’s Syndrome” and “Pervasive Developmental Disorder – Not Otherwise Specified”.  Today, the word “Autism” is used interchangeably with “Autistic Spectrum Disorder” to include these other forms.  According to the Autism and Developmental Disabilities Monitoring Network (ADDM) in 2005, Autism was measured to be present in 1 out of 110 children. In March, 2013, the National Health Statistics Report published Changes in Prevalence of Parent-reported Autism Spectrum Disorder in School-aged U.S. Children: 2007 to 2011–2012. It states that..."(t)he prevalence of parent-reported ASD among children aged 6–17 was 2.00% in 2011–2012, a significant increase from 2007 (1.16%)."

The apparent increase in Autism appears to be largely due to increased awareness, a broader definition of the condition, and a disturbing trend toward over-diagnosis.  We are now calling more people ‘autistic’ than ever before because the definition has changed.  Some states have given their education systems the power to diagnose Autism.  The states with loosest diagnostic criteria have the highest Autism rates. There may be other motivations (such as qualifying for special services). An article in reported, "Increased access to special education classes and other therapies may also be inflating the numbers, as educators and parents enroll more children in hopes of optimizing their learning environment.

CNN (12/19, Falco) reports, "Not all experts are convinced that there is a surge in autism cases. Dr. Max Wiznitzer, a pediatric neurologist at Rainbow Babies & Children's Hospital in Cleveland, OH, believes that some children may be given the autism label without meeting the actual case definition for the disorder." Wiznitzer referred "to a part in the report that said 54 percent of children were confirmed as meeting the autism spectrum disorder case definition, which means almost half did not. 'This suggests that over-diagnosis is occurring in the population,'" Wiznitzer stated.

The authors of the 2013 report conclude..."much of the prevalence increase from 2007 to 2011–2012 for school-aged children was the result of diagnoses of children with previously unrecognized ASD." This indicates that the dramatic increase in estimated rates of autism is not due to new cases, but rather due to subtle cases (based on newer criteria) were not labeled as such at earlier ages.

There may not even be an epidemic.  Many who, in the past, would have been labeled ‘retarded’, are now being labeled ‘autistic’. 

A study showed that the percentage of people with Autism is roughly the same across all age ranges. Approximately 2% of children and 2% of adults fall into this category when today's criteria are applied. "...the report suggests that, despite popular perceptions, rates of autism are not increasing, with prevalence among adults in line with that among children. It also suggests that, among adults, rates of autism remain broadly constant across age groups."

Although the actual number of cases may or may not be rising based on the most inclusive criteria, it is clear that Autism was under-diagnosed in the past.

Current research is finding increasing evidence that autism is associated with genetics and possibly other factors. In May 2011, research revealed that children who meet the criteria for autism actually have more cortical brain cells than controls. This corresponds to an increase in brain size volume to an increase in cortex surface area and an overall increase in brain weight over controls (about 70% more neurons are seen in the cortex of people with autism than controls which corresponds to a 17% increase in brain weight). These changes are observed to begin just before age 12 months. It should be noted that the MMR vaccine is not given before this time. 

Autism is not typically diagnosed until after 18 months of age.  Until then, parents may not notice any obvious difference between autistic children and other children.  Usually, we expect toddlers to be interested in other kids, to smile and interact with us. Children with Autism may not develop these traits. This is when we become concerned. However, the disorder is there before this age. Experts can spot the traits on video tapes of infants that were later diagnosed with autism. The evidence points to genetic and (possibly) environmental causes that are present before birth.

The MMR vaccine is typically given between 12 and 15 months of age. It is easy to understand why many parents of autistic children blamed the MMR. After all, the MMR preceded the diagnosis. This is what sparked interest in the British trial lawyers. But, just because one thing came before another does not mean that it caused the other.  This is a very common misconception. It gives rise to myths such as rain-dancing causing rain, and wearing a lucky hat causing your favorite team to win. Such things are purely coincidental. One tends to forget the times that it doesn't rain or that your team doesn't win (the ‘misses’). But occasionally, these things do occur (the’ hits’).  ‘Hits are remembered, ‘misses’ are forgotten.  This reinforces the myth

Facts Verses Fraud

Now, back to Dr. Wakefield. 

After being paid by the trial lawyers to find an association between MMR and Autism, he filed for a patent on a new measles vaccine. He then performed a series of tests on 12 (yes… just 12) autistic children (many of which were provided by the lawyers).  He claimed to have found a relationship between the current measles vaccine and autism.   (Hmm…this would make a new measles vaccine very lucrative, wouldn’t it?)    Before publishing his findings, he went to the media. Then, his paper was published in a medical journal (Lancet).  

However, his study was highly flawed. It never proved a link. One assistant indicated that he forged his data.  Their lab never even found the measles virus in the test subjects, as claimed in the paper.  He is currently accused of making false claims about his test subjects to make it sound as if their Autism was closely related to getting the MMR.  Also, his large pay-off was exposed (ironically by the media).  A British newspaper reported the story. A summary of investigative reporter, Brian Deer's award-winning work tells the details of the story.. Later, 10 of the 13 contributors to this paper pulled their names from it. They published a retractment saying that Dr. Wakefield’s conclusions were not supported by the evidence. He is accused of endangering the lives of his young test subjects by putting them through unwarranted procedures such as colonoscopies and spinal taps. Lancet retracted the entire paper and apologized. Dr. Wakefield was later sanctioned and forced out of England. In May, 2010, the Professional Conduct Committee of Britain's General Medical Counsel concluded that his unethical behavior was grounds for removal of his name from the medical register, banning him from practicing medicine.

In January, 2011, the British Medical Journal published an editorial making it very clear that Wakefield's study was a fraud.

But it was too late. The cat was out of the bag. The media and the anti-vaccine movement got what they wanted.  The scare was on.

Dr. Wakefield’s study was repeated by other researchers.  This time it was done with proper controls and a larger population of patients. It was published in the Public Library of Science.  This study concluded that there is no association between the measles vaccine and autism.  Did you hear about this study in the media?   Bet you didn’t.

Vaccine preventable illnesses are now returning. In May, 2010, Infectious Disease specialist, Mark Crislip MD, stated on the Science Based Medicine website..."Mumps is a timely topic as, along with measles, it has returned thanks to the work of Dr. Wakefield. His fabrication of data to falsely suggest MMR causes autism has lead to a decrease in MMR use. In some areas of England 15% of the children were not vaccinated, levels that allow the virus to perpetuate in the community. The second ‘M’ in the MMR stands for mumps. While the measles outbreak has been getting all the press, England has been plagued with mumps as well, with over 3000 reported cases. Dr. Wakefield can be credited with over 5000 (mumps plus measles) sick children."

Twenty-five studies as of 2008 have been done looking for a relationship between MMR and autism. None have been found. In Japan, kids who did NOT receive MMR where followed and found to have increasing rates of autism! In Poland, kids who had the combined MMR vaccine actually had slightly less rates of autism than kids who had the single measles vaccine and unvaccinated children. (Please don't take this the wrong way. Vaccines likely don't prevent autism). 

These studies were not widely publicized. The Cochrane Library review (the highly regarded international review of the world's medical research) concluded that the MMR vaccine is safe and has no links to autism and that "the lack of confidence in MMR has caused great damage to public health".

There have been numerous, large, multinational studies done to date on vaccine safety and effectiveness.  See the CDC's website for an extensive review.  The Institute of Medicine reported on the Immunization Safety Review Committee’s analysis of the evidence in 2004.

“The committee concludes that the body of epidemiological evidence favors rejection of a causal relationship between the MMR vaccine and autism. The committee also concludes that the body of epidemiological evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism.”

A large study from the CDC published in the Journal of Pediatrics in March, 2013 looked for possible associations between the number antigens presented in the vaccine schedule to neuro-typical children and autistic patients. There was no association found.

"I would tell an expectant mom that one of the more important things you can do to protect an infant's health is get them vaccinated on time according to the recommended schedule," DeStefano (study lead author) said. He says vaccines protect against serious life-threatening diseases and delaying them can put your child unnecessarily at risk.

"The bottom line is the number of vaccines, or the number of antigens in the current schedule, given on time ... is not associated with a risk of autism."

Do the popular media outlets report statements like this as avidly as they report the rantings of bad scientists?  No.  They do not.  Fear sells.  Science does not.

Mercury Scare and Chelation Horrors

Dr. Wakefield was not the only card up the anti-vaxers’ sleeves.  Over the last decade, there has been much talk and misunderstanding about a preservative that USED to be in routine vaccines. This preservative is called thimerosal.  It is an ethyl-mercury based preservative.  This is often confused with methyl-mercury which is toxic.  Much alarm was raised over this as a potential cause of brain toxicity.  Fair enough.  Because of political pressure, the vaccine manufacturers removed thimerosal from routine children’s vaccines in the early part of the 2000 decade. Thimerosal is no longer in the vaccines routinely given to children

Looking back at the years since thimerosal was removed, we should see a real downward trend in autism if there was anything to this idea, shouldn’t we?  What was the result?    Nothing.    There was no decline in the overall rate of diagnoses of autism and autistic spectrum disorder. In fact, (the reported) autism rates have gone up ever since. We now recognize that the actual rates have not changed, only awareness of the disorder has increased. To date, many studies have been done that show that there is no link between Thimerosal and Autism.

Furthermore, comparing ethyl -mercury to methyl-mercury is like comparing apples and oranges. The preservative ethyl-mercury has never been shown to be toxic, even at fairly large doses. It is methyl-mercury (such as from industrial waste and fires) that is toxic.  But let’s put this into further perspective. 

The adult flu shot (not the baby flu shot) is the only vaccine we routinely give that is still preserved with thimerosal.  A standard adult dose contains 25 micrograms (that’s 25 millionths of a gram) of the less toxic ethyl-mercury.  A standard can of albacore tuna contains 75 micrograms of the more toxic methyl-mercury.  Even if the 2 kinds of mercury were equally toxic, it would take 3 flu shots to equal one can of albacore tuna!  And I like tuna. Swordfish is good too. It would take about 7 adult flu shots to equal one 6 oz piece of swordfish. We could go on, but you get the picture.

This is all a mute point now. Thimerosal is no longer used as a preservative in the routine infant vaccines. 

The antivaccine movement is causing a great deal of harm.  Dangerous, unethical and completely ridiculous treatments are being inflicted upon these children and sold to good, desperate parents. These "treatments" include the sometimes deadly chelation therapy and the chemical castration of young autistic boys. 

Dr. Mark Geier and his son, David, are the leading proponents of using a drug called Lupron to chemically castrate autistic boys. Lupron has been used to chemically castrate sex offenders and to treat premature puberty. They have been doing this to kids on the misguided idea that the male sex hormone makes them more susceptible to toxins. In 2009, a Chicago Tribune investigation found the Geier's to be practicing "junk science".  Fortunately, 2 states have revoked Mark Geier's liscence to practice medicine.  David Geier, has been charged in Maryland for practicing without a licence.


Other Anti-vax Gambits

The anti-vaccine movement has now moved on. They are starting to stray away from the MMR and thimerosal rhetoric. Now they are moving the goalpost

Other "toxins" in vaccines must be doing it. There has been accusations that "antifreeze" is in vaccines (antifreeze is NOT in vaccines). Aluminum is being implicated (there are no toxic levels of aluminum in vaccines, only enough to be a good adjuvant - thus allowing us to use even LESS antigens, thus increasing both effectiveness and safety). Hydrochloric Acid (Oh NO!) is in vaccines (this is put in to neutralize the pH of vaccines so that they are no more "toxic" than water). Formaldehyde is in vaccines. This is true, in minuscule amounts. The human body naturally has formaldehyde in the blood stream in greater concentrations than that found in vaccines. These arguments make no sense and are merely used as scare tactics. 

An infant's immune system quickly develops responses to antigens from thousands of bacteria from the moment of birth. Throughout infancy, an infant must respond to millions (actually trillions) of bacteria that will colonize the large intestine. A baby will develop responses to every common virus that he/she will encounter. In contrast, the number of germs that we protect children from with the current vaccine schedule is 14. Yes, 14. To do this, vaccines use only 150 antigens total to induce immunity. Clearly, children handle this well. Prolonging the schedule would only increase the risk of disease by delaying immunity. The 2013 CDC study shows (as clearly as any study so far) that there is no correlation between the amount of antigen exposure and autism or other neurodevelopmental problems.      

The anti-vaccination movement uses popular marketing techniques like the ‘appeal to authority’. They sensationalize their claims by using popular celebrities like Jenny McCarthy. Unfortunately, real vaccine scientists have no such appeal. Ms. McCarthy has made numerous appearances on popular shows such as Oprah claiming that her child not only “got autism” from a vaccine, but that she “cured” him with restrictive dietary changes.  It must be stressed that her statements makes no plausible sense.  Nobody who is unfortunate enough to have autism has ever been cured, much less with diet.  At best, some parents reported an improvement in behavior with a gluten free diet. No studies have shown any cure and restrictive diets may cause more problems than they solve.

Other countries have their own anti-vaccination movements. For instance, in Africa, rumors are spread about the polio vaccine. Many believe that the vaccine is an attempt by the “West” to sterilize the population. Scientists were beginning to hope that polio would be eradicated and we could actually stop vaccinating ourselves against it. Unfortunately, because of these false rumors, this is no longer the case.

Another gambit is the "Too many, too soon" argument. The claim is that an infant's immune system is not ready to handle the vaccine schedule as it currently is recommended. This is simply not true. A 2010 study published in Pediatrics addressed this very notion and demonstrated that there are no neurological adverse effects from the current vaccine schedule.

Enough is Enough

We have the utmost sympathy for the families of autistic children. We hope that the cause (or causes) will be found soon. We hope that better treatments will become available. This research is ongoing but is currently being distracted. Funds that could be directed at potential causes are being used to study, re-study and study again this false notion about vaccines.  Each time, no relationship has been found. The opportunity costs are significant.

So why do so many still cling to the notion that vaccines are linked to autism, despite the mountain of evidence against this position?  It likely has to do with psychological phenomena such as cognitive dissonance, the 'sunk cost fallacy', conspiracy theory and plain denialism.  Everyone can be influenced by these forces.  They force people to maintain bogus possitions even in the light of clear, disconfirming evidence.  I recommend that we learn about these so that we may recognize them at work.

In February, 2009, a special federal court concluded the same thing. The evidence (of a link) "is weak, contradictory and unpersuasive," concluded Special Master Denise Vowell. "Sadly, the petitioners in this litigation have been the victims of bad science conducted to support litigation rather than to advance medical and scientific understanding" of autism. 

We have a civic duty to each other to vaccinate our children. Refusal based on unwarranted fear is taking a toll.

"There is evidence of an increase in vaccine refusal in the United States

and of geographic clustering of refusals that results in outbreaks. Children with

exemptions from school immunization requirements (a measure of vaccine refusal)

are at increased risk for measles and pertussis and can infect others who are too

young to be vaccinated, cannot be vaccinated for medical reasons, 

or were vaccinated but did not have a sufficient immunologic response." 

      (N Engl J Med 2009; 360:1981-1988.)


It is easier to scare than to educate.



Parents are repeatedly bamboozled by myths of the anti-vaccination movement.  This is all very difficult to watch. We have read the studies. We understand the tremendous benefit of vaccines. We understand their safety. We understand the dangers of denying vaccines.  We understand the confusion that the propaganda has caused. We understand that people only want what is best for their children. We need to help people make good decisions.

Don’t get bamboozled. Get protected. Get vaccinated.



John Byrne, M.D., FAAP

Additional Resources

Here are some additional resources to help navigate the jungle of vaccine misinformation. 

Communicating Vaccine Science to the Public 

An excellent video lecture of these issues was given at the NIH by Dr. Paul Offit. Please click on the link to view.

"Communicating Vaccine Science to the Public"

(Paul A. Offit, MD, Chief, Division of Infectious Diseases and Director, Vaccine Education Center, Children's Hospital of Philadelphia and Maurice R. Hilleman Professor of Vaccinology and Professor of Pediatrics, University of Pennsylvania School of Medicine)


An excellent source for refuting myths about each of the common vaccines, please visit  AntiAntiVax - "The Truth about the Evils of Vaccination" .

In Support of Vaccine Combinations

Here is a list of studies that support the currently recommended vaccine combinations and schedule. Click here.

Refuting Anti-vaccine Memes

References and Links

Omer, Saad B et al. "Vaccine refusal, mandatory immunization, and the risks of vaccine-preventable diseases." New England Journal of Medicine 360.19 (2009): 1981-1988.

"Measles — United States, 2011." 2012. <>

"CDC - Facts, Autism Spectrum Disorders - NCBDDD." 2009. <>

"MMR vaccine does not cause autism. - Immunization Action Coalition." 2004. <>

DeStefano F, et al "Increasing exposure to antibody-stimulating proteins and polysaccharides in vaccines is not associated with risk of autism" J Pediatr 2013; DOI: 10.1016/j.jpeds.2013.02.001.

Schechter, Robert, and Judith K Grether. "Continuing increases in autism reported to California's developmental services system: mercury in retrograde." Archives of General Psychiatry 65.1 (2008): 19.

Stehr-Green, Paul et al. "Autism and thimerosal-containing vaccines: lack of consistent evidence for an association." American journal of preventive medicine 25.2 (2003): 101

"Vaccine Safety & Availability > Thimerosal in Vaccines." 2009. <>

"Methylmercury > Mercury Levels in Commercial Fish and Shellfish." 2010. <>

Hviid, Anders et al. "Association between thimerosal-containing vaccine and autism." JAMA: the journal of the American Medical Association 290.13 (2003): 1763-1766.

Heron, Jon, and Jean Golding. "Thimerosal exposure in infants and developmental disorders: a prospective cohort study in the United Kingdom does not support a causal association." Pediatrics 114.3 (2004): 577-583.

Schechter, Robert, and Judith K Grether. "Continuing increases in autism reported to California's developmental services system: mercury in retrograde." Archives of General Psychiatry 65.1 (2008): 19.

Shattuck, Paul T. "The contribution of diagnostic substitution to the growing administrative prevalence of autism in US special education." Pediatrics 117.4 (2006): 1028-1037.

"Changes in Prevalence of Parent-reported Autism Spectrum." 2013. 23 Mar. 2013 <>

Offit, Paul A. "Thimerosal and vaccines—a cautionary tale." New England Journal of Medicine 357.13 (2007): 1278-1279.

Smith, Michael J, and Charles R Woods. "On-time vaccine receipt in the first year does not adversely affect neuropsychological outcomes." Pediatrics 125.6 (2010): 1134-1141.

Bucan, Maja et al. "Genome-wide analyses of exonic copy number variants in a family-based study point to novel autism susceptibility genes." PLoS genetics 5.6 (2009): e1000536.

"Jenny McCarthy Body Count." 2009. <>

"What's The Harm?." 2008. <>

"Autism's False Prophets." 2008. <>

"Welcome to the Vaccine Education Center | The Children's Hospital ..." 2009. <>

"One in a hundred adults have an autism spectrum disorder, says ..." 2009. <>

"Educational Assessments" Skew Autism Prevalence ... - Autism Watch." 2004. <>

"Vaccine studies: Examine the evidence - American Academy of ..." 2012. <>

"Dr Andrew Wakefield: Determination on Serious Professional ..." 2010. <>

Deer, Brian. "How the case against the MMR vaccine was fixed." BMJ 342 (2011).

"Andrew Wakefield - the fraud investigation - Brian Deer." 2004.<>

John Thomas, JD. "“Paranoia Strikes Deep”: MMR Vaccine and Autism - Psychiatric Times." 2010. <>

"Controverisal autism doctor suspended in Washington -" 2011. <>

Courchesne, Eric et al. "Neuron number and size in prefrontal cortex of children with autism." JAMA: The Journal of the American Medical Association 306.18 (2011): 2001-2010.

Hazlett, Heather Cody et al. "Early brain overgrowth in autism associated with an increase in cortical surface area before age 2 years." Archives of general psychiatry 68.5 (2011): 467.

Omer, Saad B et al. "Vaccine refusal, mandatory immunization, and the risks of vaccine-preventable diseases." New England Journal of Medicine 360.19 (2009): 1981-1988.

"Autism Decisions and Background Information | US Court of Federal ..." 2009. <>

"NIH VideoCasting - Communicating Vaccine Science to the Public." 2012. <>