by Vivian Chou
figures by Daniel Utter

If you have been following the 2016 US presidential elections, you are, in all likelihood, aware of the controversy surrounding mandatory childhood vaccination. Vaccines have risen to the limelight in recent years, but their history is much longer than that. Ever since the first vaccination was scientifically documented in 1798 [1], they have reshaped the landscape of human health and medicine. The impacts of vaccines have ranged from the 1979 eradication of polio in the US [2] and the 1980 eradication of smallpox worldwide [3], to prevention of cancer of the liver [4] and the cervix [5]. In fact, vaccines have been so influential that some scientists consider them among the greatest successes in public health [6].

But not everyone shares this optimistic view of vaccines. Today, anti-vaccinationists (sometimes known as “anti-vaxxers”), who include parents, politicians, religious leaders, and more, strongly oppose vaccination, particularly childhood vaccination. At its core, the anti-vaccination movement argues that vaccines are unnecessary, ineffective, or dangerous. But is this truly the case? A closer look at the evidence surrounding vaccinationists suggests that while the anti-vaccinationist ideals are compelling, a more accurate picture of vaccination may be found elsewhere.

What vaccines do: the science at the heart of a controversy.

When a pathogen [7], such as harmful bacterium or virus, infects the body for the first time, the immune system [8] will quickly recognize it as an “invader” based on molecular features specific to the pathogen (known as antigens) (Figure 1A). In response to these antigens, the body produces molecules called antibodies [9] that enable our immune system to track down and kill the pathogen.

The first time the body encounters a pathogen, it takes days to assemble enough antibodies to defeat the infection. In that time, the pathogen has the opportunity to attack the body, causing us to experience symptoms of illness. After this first encounters, the body will memorize what the antigens look like, so that if the same pathogen strikes again, we will be able to launch a stronger, faster defense against future invasions.

Vaccines teach the body to recognize a pathogen. Specifically, vaccines contain the same antigens as pathogens (Figure 1B), but in a weakened or dead form, so that the body can learn what the pathogen looks like and produce antibodies (Figure 1C) in a safe and comparatively controlled manner. Thus, when the body encounters the real pathogen, it is already trained and ready to eliminate the pathogen before it can do any damage (Figure 1D).

Importantly, a vaccine protects not only the individual to whom it is administered, but also the entire population. When the number of immunized individuals within a population reaches a critical threshold, herd immunity [10] is conferred (Figure 2). Herd immunity protects the entire population, even those who are not vaccinated are protected from disease. The percentage of the population that must be immunized to achieve herd immunity varies for individual diseases, with thresholds for common diseases ranging from 75-94% [11]. Herd immunity is crucial to protecting those who are not eligible for vaccines, such as infants, pregnant women, and immunocompromised adults. This means that while vaccines may seem like a personal choice, vaccination protects the entire population—and accordingly, failure to vaccinate could have negative population-level consequences.

Figure 1: Building immunity through vaccination. (A) Pathogens such as bacteria and viruses have molecular signatures called antigens (green triangles) that can be recognized by the body’s immune system. (B) Vaccines contain these antigens (or parts of them), without the dangerous parts of the pathogen that cause disease. (C) Upon injection of the antigens into the body, our immune systems generate antibodies (Y-shapes) which recognize the antigen. (D) If an infection by the same pathogen occurs in the future, the immune system already has antibodies at the ready. The body can rapidly recognize the pathogen based on its antigen and launch a fast, effective defense.

Are vaccines truly that effective?

Though no vaccine is 100% effective, many come quite close. For instance, two doses of the chickenpox vaccine are 98% effective against any form of chickenpox [12]. In fact, many vaccines against deadly diseases – such as smallpox [13], yellow fever [14], measles [15]- are over 95% effective, as long as they are administered on schedule. History has also attested to the effectiveness of vaccines. Immediately following the licensing of the measles vaccine in 1962, the number of measles cases in the US dropped dramatically [16] (Figure 3).

Figure 2.: Herd immunity. (A) When no one in a population is vaccinated, infections can spread rapidly and become an outbreak. (B) When some individuals are vaccinated, they are individually protected from an infection. However, if the number of people vaccinated is below the critical threshold for herd immunity, the infection can still spread. (C) When a large enough proportion of the population is vaccinated, herd immunity is conferred. Outbreaks are prevented from spreading, and individuals who are unvaccinated are still protected.

Some anti-vaccinationists have claimed that the decrease in measles shortly after the vaccine was introduced is purely coincidental, and that other measures, such as improved hygiene and sanitation, are mainly responsible for the decline in measles and other than diseases. If this were true, we would expect all diseases to have begun their most drastic declines around the same time. However, the sharpest drop in polio cases occurred shortly after the licensing of the polio vaccine in 1955 [17], in the late 50’s — years before the measles decline occurred (Figure 2). Similarly, cases of rubella declined sharply after 1969 [18], when the vaccine was first licensed (Figure 3).

The observation that a decline in the number of disease cases occurs right after the introduction of the vaccine for that disease argues very strongly that it is, indeed, the vaccine which is responsible for the reduction in disease. While improvements in sanitation and healthcare were doubtless beneficial, the availability of vaccines was still the major determinant of the spread of a disease.

Figure 3: Cases in the US over time of measles (top), rubella (middle), and polio (bottom). Dashed lines represent the years in which the vaccine for a given disease was first licensed by the US Food and Drug Administration (measles – 1963, rubella – 1969, polio – 1955).

A tale of autism and vaccines

Among the most popular arguments within the anti-vaccination movement is that vaccines can do more harm than good – for instance, by causing autism [19], a developmental brain disorder known to impair social interaction and communication.

This argument was popularized by British surgeon Andrew Wakefield [20], “the father of the anti-vaccine movement” in his 1998 article in The Lancet [21] that claimed a link between autism and the measles, mumps and rubella (MMR) vaccine. The article describes a study of twelve children who had begun exhibiting symptoms of autism, as well as gastrointestinal issues, shortly after receiving the MMR vaccine [22]. The paper, and Wakefield’s bold assertions to the media of an MMR-autism link, sparked immediate controversy and quickly became a rallying point for parents opposed to the MMR vaccine, or vaccinations in general.

Within months of the Wakefield study, other scientists conducted independent investigations, which failed to corroborate Wakefield’s findings [23]. Additional studies from the UK in 1999 [24], Finland [25] and Denmark in 2002 [26], and Japan in 2005 [27] similarly failed to confirm the Lancet article. In 2014, Australian scientists analyzed the combined results of ten prior studies — collectively involving over 1.2 million children — and similarly found no relationship between vaccines and autism [28]. Most recently, a US study published in April 2015 has once again shown that the MMR vaccine does not increase the risk of developing autism, even for those who are genetically predisposed to the disorder [29].

In 2004, British investigative journalist Brian Deer presented evidence that Wakefield may have falsified data in his publication [30]. Questions against Wakefield’s findings continued to mount, until January 2010, when the General Medical Council ruled that Wakefield guilty of serious misconduct [31], and the Lancet retracted the original 1998 article [22]. A few months later, Wakefield was removed from the UK medical register and barred from practicing medicine in the UK [32].

The enduring popularity of the autism-vaccine story may be fueled by stories within the anti-vaccination movement itself. Parents have shared stories of children who began developing signs of autism shortly after receiving vaccines, and conclude that vaccines are in fact the cause of autism. However, the onset of autism typically occurs at 2-3 years of age [19], which is around the same age that children receive most of their vaccines.

Additionally, anti-vaccinationists supporting Wakefield’s views often point to the rise of autism diagnoses in the US [33] – more than ten-fold what it was in the 1970s and 1980s – as evidence of an autism-vaccine link. In actuality, the causes of the increase in autism diagnoses are far more complex.

The rise in autism diagnoses is due, in part, to changes in the definition of autism. In general, the definition of autism has become increasingly detailed and inclusive, and thus, more children today are diagnosed with the disorder [34]. In fact, the same symptoms that would be considered “autistic” today may have led to a different diagnosis, such as mental retardation, several decades ago.

Interestingly, the city of Yokohama, Japan has not administered the MMR vaccine to any children born since 1993. Yet, autism rates have increased even among these unvaccinated children [27]. Thus, even as scientists continue to untangle the exact causes of autism, one thing remains unchanged: no one has yet found a scientifically sound and robust link between vaccines and autism.

Are there dangers of vaccines beyond autism?

Besides autism, anti-vaccinationists are often wary of other potential ill effects of vaccines. In some cases, these concerns are reasonable. Many vaccines are not recommended for individuals who have serious allergies to the ingredients, and for those with a weakened immune system due to diseases such as HIV/AIDS or cancer [35]. Additionally, the seasonal flu vaccine can cause life-threatening symptoms in people with Guillain-Barré syndrome [36]. In rare cases, shoulder injury related to vaccine administration (SIRVA) [37], causing prolonged pain and stiffness, can result when vaccines are injected too high up on the arm. However, while there are certainly situations where vaccines can cause severe side effects, they are quite rare.

The most common side effects of vaccines, such as discomfort at injection site, fatigue, and fever, are minor and temporary [38]. Fevers can very occasionally worsen into seizures after vaccination [39]. While many parents worry that fever or febrile seizure are dangerous, neither is life-threatening nor permanently damaging. Febrile seizures are not rare: up to 5% of children experience them within their lifetime when they experience fevers from a variety of causes, such as the flu and cold — not just from vaccines [40]. In fact, vaccines may even prevent febrile seizures, as they protect against many diseases associated with febrile seizures, such as measles and chickenpox, among others.


For many, the question of whether or not to vaccinate is a daunting one. The vaccination debate is plagued with a myriad of contradictions and conflicts, and it can be difficult to navigate these turbulent waters. However, with careful investigation and analysis of the available evidence, an accurate picture may begin to take shape.

Vaccines, like any other medical technology, have advantages and pitfalls alike. History and science have repeatedly shown that the advantages of vaccination far outweigh the pitfalls, and that many of the negatives can be avoided with proper judgment. Yet mistrust of vaccines has persisted, despite ample evidence that they are safe, potent, and effective, and further evidence that soundly counters claims such as causing autism. And despite all the vocal opposition to vaccines, none of the attempts to prove the ineffectiveness or dangers of vaccines have stood up over time and rigorous testing.

Many questions in science and medicine are confusing and frustrating, but fortunately, the question of vaccination need not be one of them. Because for vaccines, the verdict is already in: guilty of being safe, effective, powerful, and highly recommended.

Vivian Chou is a Ph.D. student in the Biological and Biomedical Sciences Program at Harvard Medical School.

Selected references for further reading

”Pathogen.” Science Daily. Accessed December 2015.
Zimmermann, KA. “Immune System: Diseases, Disorders, and Functions.” Livescience. October 2014. Accessed December 2015.
Willingham, E & Helft L. “What is herd immunity?” September 2014. Accessed December 2015..
”Vaccines are effective.” Accessed December 2015.
”What is autism?” Accessed December 2015.
Deer, B. “Andrew Wakefield and MMR: the investigation.” The Sunday Times. February 2004. Accessed December 2015.
Willingham, E. “Increase in autism diagnoses not an increase in autism. Forbes. July 2015. Accessed December 2015.
”Childhood vaccines and febrile seizures.” CDC. Accessed December 2015.

Full list of references

[1]Riedel, S. “Edward Jenner’s historical invention of the smallpox vaccine.” Proc Bayl Univ Med Cent. 2005.
[2]”Keeping the US polio free.” CDC. Accessed December 2015.
[3]”Smallpox.” WHO. Accessed December 2015. .
[4]”Hepatits B.” WHO. Accessed December 2015.
[5]”HPV vaccine information for young women.” CDC. Accessed December 2015.
[6]Schlenoff, DC. “What are the 10 greatest inventions of our time?” Scientific American. November 2013. Accessed December 2015.
[7]”Pathogen.” Science Daily. Accessed December 2015.
[8]Zimmermann, KA. “Immune System: Diseases, Disorders, and Functions.” Livescience. October 2014. Accessed December 2015.
[9]Mandal, A. “What is an antibody?” News Medical. Accessed December 2015.
[10]”Community immunity (“herd” immunity).” NIH. Accessed December 2015.
[11]Willingham, E & Helft L. “What is herd immunity?” PBS NOVA. September 2014. Accessed December 2015..
[12]”Varicella vaccine effectiveness and duration of protection.” CDC. Accessed December 2015.
[13]”Smallpox fact sheet: vaccine overview.” CDC. Accessed December 2015.
[14]”Yellow fever.” WHO. Accessed December 2015.
[15]”Measles vaccine.” CDC. Accessed December 2015.
[16] ”Vaccines are effective.” Accessed December 2015.
[17] ”Poliomyelitis.” CDC. Accessed December 2015.
[18] ”Rubella.” CDC. Accessed December 2015
[19] ”What is autism?” Autism Speaks organization. Accessed December 2015.
[20] Ziv, S. “Andrew Wakefield, father of the anti-vaccination movement, responds to the current measles outbreak for the first time.” Newsweek. February 2015. Accessed December 2015.
[21] in The Lancet journal.
[22] Wakefield, A, et al. “RETRACTED: Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children.” Lancet. 1998.
[23] Peltola, H, et al. “No evidence for measles, mumps, and rubella vaccine-associated inflammatory bowel disease or autism in a 14-year prospective study.” Lancet. 1998.
[24] Taylor, B, et al. “Autism and measles, mumps, and rubella vaccine: no epidemiological evidence for a causal association.” Lancet. 1999.
[25] Mäkelä, A, et al. “Neurologic disorders after measles-mumps-rubella vaccination.” Pediatrics. 2002.
[26] Madsen, KM, et al. Population-based study of measles, mumps, and rubella vaccination and autism. N Engl J Med. 2002.
[27] Honda, H, et al. “No effect of MMR withdrawal on the incidence of autism: a total population study.” J Child Psychol Psychiatry. 2005.
[28] Taylor, AL, et al. “Vaccines are not associated with autism: an evidence based meta-analysis of case-control and cohort studies.” Vaccine. 2014.
[29] Jain, A, et al. “Autism occurrence by MMR vaccine status among children with older siblings with and without autism.” JAMA. 2015.
[30] Deer, B. “Andrew Wakefield and MMR: the investigation.” The Sunday Times. February 2004. Accessed December 2015.
[31] Triggle, N. “MMR scare doctor ‘acted unethically,’ panel finds.” BBC. January 2010. Accessed December 2015.
[32] Meikle, J and Boseley, S. “MMR row doctor Andrew Wakefield struck off register.” Guardian. May 2010. Accessed December 2015.
[33] Dohemy, K. “Autism cases on the rise; reason for increase a mystery.” WebMD. March 2008. Accessed December 2015.

[34] Willingham, E. “Increase in autism diagnoses not an increase in autism. Forbes. July 2015. Accessed December 2015.
[35] ”Who should NOT get vaccinated with these vaccines?” CDC. July 2011. Accessed December 2015.
[36] ”Guillain-Barré syndrome.” MayoClinic. Accessed December 2015.
[37] Zhang, S. “Why are cases of shoulder injuries from vaccines increasing?” Wired. September 2015. Accessed December 2015.
[38] ”Side Effects from Vaccines.” Immunize for good. Accessed December 2015. .
[39] ”Febrile seizures following childhood vaccinations, including influenza vaccination.” CDC. Accessed December 2015. .
[40] ”Childhood vaccines and febrile seizures.” CDC. Accessed December 2015.

44 thoughts on “To vaccinate or not to vaccinate? Searching for a verdict in the vaccination debate

  1. Oh my doctor, please burn your degree. You should never practice medicine and treat any autistic person. And the verdict is never in with science Doctor. It’s an emerging field with constant analysis and discoveries made each day, each year. How utterly arrogant and idiotic of you to assume it’s over.

    1. Following this logic, let us all negate the THEORY of gravity and for the time being (because who knows what the future holds for gravity and science) we shall all assume another more possible explanation: the earth sucks!!!!! Perfectly logical and fits the evidence for me…

  2. Interesting article. I definitely believe in vaccinations. Mainly because of the “herd”. I am immunosuppressed with no immunity against Pneumonia, pertussis and I’m told it likel y is hereditary and while I’ve had immunizations, titers show they have not been effective at all. Thus, I depend on the public being immunized to help protect me.

  3. Vaccination is fake science and more and more people are waking up about it. Stop the lies, stop the half truths and bring out the real science behind vaccines. Somewhere in some book it says, “the love of money is the root of all kinds of evil. ” If vaccines were so safe why did congress have to pass a law to protect the highly profitable money sucking drug companies owned by the elite multi billionaires from liability and create a taxpayer fund to pay for injuries caused by vaccines? The National Childhood Vaccine Injury Act of 1986, acknowledged that vaccine injuries and deaths are real and that the vaccine injured and their families should be financially supported and that vaccine safety protections were needed in the mass vaccination system. God’s Word says, No one will be able to buy or sale unless he or she has the mark of the beast system. The beast is the one world government. In the book of Revelation it says in the last days evil people will not turn from their wicked ways. Judgment Day is coming!

  4. Sudden infant death is directly related to vaccinations. Quit the BS. .Selfish. Myopic willfuly ignorant fools! Until vaccines are made without toxins they will continue to intermittently injure and kill innocent babies. Nobody can predict which baby will have a life threatening reaction to a particular vaccine (s). And we know some vials are “overfilled”….and others are related after they expired….

  5. Evil. Liars! You know darn well vaccines have killed babies, and yet you continue to deceive the public. May you die of brain cancer. Pigs.

    1. Wow, Paul. Check numbers of deaths from diseases prior to vaccines and the numbers of deaths after vaccines. Name calling and high emotions don’t change the fact that vaccines do more good than harm.

  6. It is understandable that some people support and some people don’t support vaccines. But this is a matter of public health and safety. The majority should decide what to do. If more people believe that it is right to have vaccines then the matter should go to them. I also think it is better to be on the safe side than in danger of dangerous viruses and diseases being infected into millions of people.

  7. I read this article with interest, and was disappointed because it provided a one sided view that children should be vaccinated. I am not anti vax, but rather pro children. I think some vaccines may be good and each parent should have the right to decide if a particular vaccine is right for their child. I think more information needs to be researched. As the article states, there were cases of autism that were blamed on the vaccines. There were payouts and I don’t think that it ever went to trial. Since then the amount of mercury in these vaccines has been reduced. So the vaccine investigations in the paper you site do not test the same vaccines that were given to the children who may have become autistic from them. It may have been coincidence that those kids became autistic and it may be do to something else, perhaps the the vaccines. Because of the law suits that happened with these autism cases, pharmaceutical companies were afraid to research new vaccines and thus were given immunity by Congress. What happened was an explosion of vaccines. These vaccines were not thoroughly tested since the drug companies didn’t have to worry about lawsuits. Vaccines were increasingly made for as many things that these companies could think of. They seem to be rushed through the FDA/CDC. The 2017 schedule gives 28 doses of 10 different vaccines (3 doses of HepB, 3 doses of rotavirus, 4 doses of DTap, 4 does of Hib, 4 doses of polio, 4 doses of pneumococcal, 2 doses of influenza, MMR, Varicella, and 2 doses of Hep A) more than twice the number of vaccines even in 1997 (3 doses HepB, 3 doses DPT, 3 doses of Hib, 2 doses of MMR, and 2 doses of polio which is a total of 13 doses of 5 different vaccines. At this point I question something from the article which said vaccines were working. If vaccines are working, why has the dose for certain vaccines increased in the first 18 months of life. The doses of polio went from 2 to 4, 3 doses of DPT to 4 doses of DTap, 3 to 4 doses of Hib. If a vaccines works with two doses why the need to increase it to 3. Another question I have is why do different countries have different schedules. Why does Israel give the varicella (chicken pox) at age 5 and we give it at 12-15 months? If vaccines are supposed to keep our children healthy, then why are our children less healthy than ever. In 2013 the Institute of Medicine of the National Academies said that there needs to be more study of the immunization schedule: “the number, frequency, timing, order, and age at the time of administration of vaccines has not been systematically examined in research studies.” The federal government disagrees.
    Not too long ago, the cigarette companies paid scientists to promote cigarette smoking saying that it was safe to smoke. How do we know that is not happening now with the scientists that the pharmaceutical companies employ. When Congress took away the American people’s right to sue a vaccine maker for damages, it took away a type of oversight that is needed. There can’t be individual or class action cases that would seek to discover the truth. For the most part we only have the word of the scientists who are being paid by the drug companies.
    There was a recent Dutch study of children in Africa who were given the DPT as babies and those who were given the vaccine were 10% more likely to die within the next two months than those that did not receive the vaccine. This was a study that Robert F. Kennedy, Jr. mentioned in an interview I saw on Fox News. He did not say which dose or how old the children were.He just referred to them as babies. He also said during the interview that he is not anti- vaccine, his own children were vaccinated (with a schedule that has less vaccines and less doses), but anti the current schedule because he does not feel it has been tested enough. At the end of the interview, he thanked the interviewer for inviting him on and mentioned it was the first invitation he has had to a major news show. He has tried to get interviews on all the major news stations. He said that the news shows get a lot of money from pharmaceutical advertising which is a way of keeping the discussion out of the news.
    For any one who wants more information on vaccines I would suggest “Vaxxed” and “The Truth about Vaccines.”

    1. Susan, well said. I agree with the statement that I am not necessarily anti-vax, but pro-child health. Vaccines do NOT make your child any healthier. The only thing they claim to do is reduce incidence of certain diseases.

      But the real question is, at what cost? I used to be pro-vaccine, until I began looking objectively at the issue, at the research, at the various studies, at how other countries vaccinate, etc. And I’ve come to the conclusion that for most of the diseases, the risks of vaccines outweigh the benefits.

      For example, here is the conclusion of the abstract of the study that someone posted below. “In conclusion, vaccinated homeschool children were found to have
      a higher rate of allergies and NDD ( neurodevelopmental disorders) than unvaccinated homeschool children. While vaccination remained significantly associated with NDD after controlling for
      other factors, preterm birth coupled with vaccination was associated with an apparent synergistic increase in the odds of NDD. Further research involving larger,
      independent samples and stronger research designs is needed to verify and understand these unexpected findings in order to optimize the impact of vaccines on
      children’s health.”

      It’s really significant that this article has concluded what anti-vaxers have been saying all along. That there is a statistically significant increase in side effects (primarily NDD and allergies) in children from vaccines, and that those side effects are much more likely to occur in pre-term children. The article calls for more study in larger sized trials. And they ever so delicately dance around the issue that indeed vaccines are not the panacea that people think they are. It’s not surprising, since if they were to actually recommend no vaccines, they’d be lynched by the currently medical and pharmaceutical establishment.

  8. One question, if vaccines are soooo safe, what’s the reason that pharmaceutical companies are not liable for them unlike other drugs?
    Ah, one more thing, according to the vaccines insert, many risks are listed, including dealth, but I am guessing this is not worth to mention in your “scientific article”, it only happens if the person is unlucky .

    1. I believe that the reason that liability for vaccines works differently than for other drugs is due to the fact that anti-vaccine thinking resulted in an increase in lawsuits against pharmaceutical companies that blamed them for medical issues that were unlikely to be caused by vaccines. Congress/the supreme court decided that because this large number of lawsuits was not based in science and could greatly harm reduce the availability of vaccines, it was in the interest of public health to prevent such lawsuits. I don’t know if that’s the best solution to this problem, but it is a problem when children whose parents want them to get vaccines to prevent deadly illnesses can’t get them.

      And many drugs have very serious warnings that include death listed as possible side effects. For vaccines, the point remains that there is no causal relationship between vaccines and any of the serious negative side effects that people often associate with vaccines (e.g. autism, death).

  9. Hey. Thanks for the article and citations/sources. This was easy to read, covered major points of interest (based on conversations I’ve had in the past regarding this topic), and something I can pass on to others interested in the topic.

    Just to point out a few non-factual errors in the article:
    1. “Figure 2.: Herd immunity. (A) When no one in a population is vaccinated, infections can spread rapidly and become an outbreak that.” Might want to fix “that.”
    2. A couple copy references to Figure 2 that more likely were meant to say Figure 3; both are under the sub header “Are vaccines truly that effective?”

  10. My gosh how fraught is this issue with controversy!
    (1) Neither side is 100% true or false – both sides are a mix of true and false;
    (2) I’ve have had the flu twice in my adult life; both times it almost killed me. For several years in between those two times I stopped getting vaccinated due to the bad PR that was emerging; however, after that last case in 2006, I realized I had to minimize my chances of getting the flu again. So I have been getting vaccinated every year since that time. This year, I also got a pneumonia vaccination. And of course I had the myriad of childhood vaccines, and I still get a tetanus shot every five years. I take care of an elderly person, so that is all the more reason to get vaccinated — to minimize the chances of conveying flu virus to her.
    (3) One thing surprised me in Chou’s article: she uses correlation to support her argument that vaccinations reduce disease incidence. This is the same “logic” that anti-vaxxers use to “prove” their contentions that vaccinations cause autism. Scientists are forever reminding us that correlation is NOT causation. So the fact that a Harvard Med School PhD student fell into this same pitfall really surprised me. I thought she was “above” that.

    1. Thanks for your comment. It is always good to remember that correlation does not prove causation. However, there is sometimes no other way to do an experiment except using correlation (it would be unethical to just vaccinate some populations of people but not others and see how many die in each group). In these kinds of cases, it is important to consider other factors that might cause the effect you are looking for, which as the author mentions, scientists have done here. It’s not invalid to use correlation in science–it is just important to remember what you can actually conclude and what you can’t and how likely what you observe is to be caused by what you think it is caused by.

      This would be true for vaccines and autism, too–if there were a strong correlation, we should be worried, However, the is not. As you can read here, the only evidence that there ever was that vaccines cause autism (which is, indeed a correlation), doesn’t hold up–the correlation doesn’t even exist if scientists look at more people. So while we haven’t done an empirical test to show that vaccines don’t cause autism; she’s saying that there is no evidence that currently exists, correlative or otherwise, that points to vaccines causing autism: “no one has yet found a scientifically sound and robust link between vaccines and autism.”

          1. OK, here is your statement: “The observation that a decline in the number of disease cases occurs right after the introduction of the vaccine for that disease argues very strongly that it is, indeed, the vaccine which is responsible for the reduction in disease.” THAT is a perfect example of trying to make the case that correlation is causation.

          2. That’s not my statement–that’s a quote from the article (I am not the author). Which is, actually, what I was referring to in the first paragraph of my comment (sorry if that was unclear). While correlation can’t PROVE causation, it’s not always invalid to use correlation as evidence as long as you consider the pitfalls of using correlation as evidence. In the paragraph previous to the one you quote, the author explains why this decrease in disease incidence is unlikely to be due to some other factors. Does this mean that there is not some unknown factor that could cause the decrease in incidence? No–that’s why correlation correlation can’t prove causation. However, given that there are both empirical studies showing that giving someone a vaccine makes them less likely to get the disease (studies/figures on that cited in the first paragraph of that section) and the lack of other reasonable factors that could have reduced the incidence of these diseases, the correlative evidence is strengthened in this case. Notice that the author says “argues very strongly” not “proves” — I think that’s actually a perfect example of drawing a measured conclusion from correlative evidence after considering several angles NOT saying correlation = causation.

            BTW- for the sake of transparency, my first comment stated a fact from the article incorrectly because of the omission of a “n’t”

          3. I understand your point, and I am playing devil’s advocate here because I see the anti-vaxxers often using correlation to bolster their arguments too, which is then cited by other scientists as “only correlation, not scientific evidence”. I wish that both sides could consider each other’s arguments more fully and objectively, because honestly, I don’t think either side is 100% correct or 100% wrong.

            Thank you for responding.

          4. If you don’t mind sharing, what do you find un-convincing about this article? How do you think her argument is wrong? I agree that it’s important to listen to all sides–especially on issues that are important to public health. So in that spirit, what do you think the scientists are missing in their conversation with anti-vaxxers?

          5. I do not believe they are directly addressing all the evidence that the anti-vaxxers are citing. I will reread the article more critically in hopes of answering your question. Surely you must be familiar with some of their points. Maybe for starters you could look over some of this material and give me your honest opinion. I did post them elsewhere in the comments, but here they are again:



          6. Sorry–I haven’t had a chance to look at these in detail yet, but it is true that live viruses can (albeit rarely) lead to someone who has been recently vaccinated giving someone else the disease. However, I don’t see this as a reason not to vaccinate, as epidemiological studies suggest that these vaccines lower disease incidence overall. Also, the virus in live virus vaccines is weakened, meaning that even if it spreads to another person, it’s much less likely to spread widely than the actual virus (which would spread if people weren’t vaccinated).

          7. Typo — second paragraph — “argues asserts”.

            “Within months of the Wakefield study, other scientists conducted independent investigations, which failed to corroborate Wakefield’s findings [23]. Additional studies from the UK in 1999 [24], Finland [25] and Denmark in 2002 [26], and Japan in 2005 [27] similarly failed to confirm the Lancet article. In 2014, Australian scientists analyzed the combined results of ten prior studies — collectively involving over 1.2 million children — and similarly found no relationship between vaccines and autism [28]. Most recently, a US study published in April 2015 has once again shown that the MMR vaccine does not increase the risk of developing autism, even for those who are genetically predisposed to the disorder [29].” ———— Do you know, by any chance, who funded these studies in the other countries? Some anti-vaxxers claim that Big Pharma is behind all the research which has concluded that vaccinations are safe.

            Also, have you watched the documentary called “Vaxxed”? It would be great if you or other professionals at Harvard Medical School would address each case they raise, and publish it on this and other websites, to help the general population understand was is true and what is not. That would be most helpful to folks like me who try to keep an open mind.

          8. Thanks! I will fix the typo. Studies usually say who they were funded by (although I realize that that information may be hard to find if it’s behind a paywall), and always have to say if their funding could be considered a conflict of interest (which a vaccine study funded by pharma would definitely fall under). People might argue that these studies would just lie and say they weren’t funded by pharma, but actually two of these studies cited here (#23 and #25) does say that it received partial funding from Merk). #24 was funded by the Medicines Control Agency (part of the UK government), #26 was funded by the Danish National Research Foundation; the National Vaccine Program Office and National Immunization Program, Centers for Disease Control and Prevention; and the National Alliance for Autism Research, and #27 and #28 don’t mention where their funding is from or cite conflicts of interest, #29 is funded by the National Institute of Mental Health, National Institutes of Health, and the US Department of Health and Human Services.

            So it’s true that some of this research discounting the Wakefield paper is partially funded by Merk, but it was done at independent university labs, and it would be highly unethical for them to do studies differently because of their funding source. Either way, there are at least five studies funded by government agencies that support these studies, so it’s not true that Big Pharma is behind all of the pro-vaccine studies.

            I have not watched “Vaxxed,” but I will see if someone is interested in writing such an article for our website.

          9. Vivian, Please let me know if you can get some professionals from Harvard Med School to watch and respond to “Vaxxed.” I think it’s very important to get that professional, informed response out into the general public. Also, would you please tell me your credentials so that I may properly reference your statements? Thank you!

          10. Hi, I’m not Vivian. I’m the editor in chief of this blog. I am a PhD student in biomedical science.

          11. All this time I thought I was communicating with Vivian. Do you know what her credentials are? And your name please? Thanks, –Dave

          12. I have ongoing discussions with anti-vaxxers, and if I could passing along the credentials of the people I am quoting it would lend more weight to my perspective. That is why I am particularly interested in whatever the professionals at Harvard Medical School have to say on this subject.

          13. Another comment Vivian. To your point: “So it’s true that some of this research discounting the Wakefield paper is partially funded by Merk, but it was done at independent university labs, and it would be highly unethical for them to do studies differently because of their funding source. Either way, there are at least five studies funded by government agencies that support these studies, so it’s not true that Big Pharma is behind all of the pro-vaccine studies.”
            It might be highly unethical, but the fact is people do bow to pressure, or to the lure of money. Unfortunately, that is not at all uncommon in the world, especially in the US where money rules over all else.

          14. And that’s the reason they have to declare where the money came from. However, I’d be more wary of a study done by a pharmaceutical company than a study done by an academic lab funded by a pharmaceutical company.

  11. Obviously this a very biased article. Any of these so called articles or “research” you read or see you have to 1st find out who funded them and who gets what money.
    I know of 3 people (close friends) whom died exactly after 6 months in exactly the same agony and pain right after receiving a Flu Shot (2012)! One of these friends lived in England, 2 in USA.

    I have seen perfectly healthy and happy children becoming a vegetable right after getting their so called vaccines!!
    I also believe Autism, Alzheimer and many of these newly invented diseases are direct result of the vaccines.
    Why don’t people ask questions like why should we inject an Unknown substance directly into our bloodstream? Is there an Epidemic going on?
    Why don’t these brainwashed doctors send these vaccines into a lab to be tested first before injuring or killing someone’s baby?
    There was a time when they exposed a horse to snake poison or a disease to get the antibodies to be used as “vaccine” a long time ago but these vaccines today are Not anything like that.
    Do more research from sources which do not deal with money nor fear.
    Thank you!

    1. Hello, if you have specific concerns about specific references, then feel free to state them. Our authors are careful to cite articles written by credible authors from diverse backgrounds, such as government research agencies, academia, and non-profits. We take the time to provide evidence for our claims–please do the same if you would like to assert that autism and Alzheimer’s disease are “invented” diseases that are caused by vaccines.

      There are many, many well-respected and unbiased studies that have deemed vaccines to be safe. Feel free to check out the 5 papers suggested here by the CDC ( The Institute of Medicine has reviewed over 1,000 research articles and has come to similar conclusions ( And safety tests are in fact performed on vaccines. Just like all drugs, vaccines must be tested in human clinical trials before they can be approved for sale on the market and widespread use. More information about that extensive and rigorous process can be found here:

Leave a Reply

Your email address will not be published. Required fields are marked *