Explainer: Vaccines are not linked to autism | Science News for Students

Explainer: Vaccines are not linked to autism

Ignore a long-debunked study and internet scare-mongers. Science still confirms no causal tie
Apr 4, 2019 — 6:35 am EST
an autistic girl sitting on a kitchen counter and blowing bubbles

A now-discredited study once linked vaccines and autism. But many studies have since shown that vaccinations don’t lead to the brain disorder.

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Study after study confirms that vaccines are safe and save lives. So, most parents say yes to vaccines. They want to protect their children from diseases that can cause permanent harm or even death. Yet some parents say no. Many of these people base that refusal on a 1998 study that claimed to find a link between autism and vaccines.

Autism is a disorder that affects how the brain develops. Its symptoms can range from mild to severe. These symptoms can start to appear around the same time that kids get many of their vaccinations. So the 1998 study worried parents. Many feared their kids might develop autism after getting the MMR vaccine. That vaccine gets its name from the fact that it protects against three major childhood diseases: measles, mumps and rubella.

In fact, the 1998 study’s claims were false. Scientists debunked the report long ago. Still, some people haven’t learned about that or refuse to believe data that find no signs of an autism link. None. The most recent of these follow-up studies — and the largest — came out March 5, 2019 in the Annals of Internal Medicine. Like the others, it found no link between autism and vaccines.

In this new study, Anders Hviid of the Statens Serum Institut in Copenhagen, Denmark and his colleagues collected data on more than 657,000 Danish children between 1999 and 2013. They followed the children from age 1. Denmark provides free vaccines for children. As a result, most families chose to have their kids receive the MMR vaccine. But not all.

Over the study period, 6,517 children were diagnosed with autism. But the team found that children who got the MMR vaccine were no more likely to be diagnosed with autism than were those who didn’t get it. Groups that might be more susceptible to autism also did not have an increased risk from being vaccinated.

About that 1998 study

The initial claim of a possible autism link appeared in The Lancet. A small study, it had focused on just 11 boys and one girl with autism. Led by a surgeon in England, Andrew Wakefield, this study linked autism in these kids to their having gotten the MMR vaccine.

That 1998 study had not been performed well. Later research would show this. That didn’t stop parents around the world from panicking over its claims, however.

Many scientists also were concerned about the claims by Wakefield’s group. Some of them tried to repeat the study. But they didn’t get the same result. Much larger studies investigated further. They, too, failed to find support for the claim made by Wakefield’s team. More than that, research turned up evidence that Wakefield committed fraud. A series of articles published in BMJ, a British medical journal, outlined much of the evidence for that in 2011.

Despite all of this, the 1998 study’s claims have mushroomed online. One 2016 study in the Journal of Communication in Healthcare found nearly 500 anti-vaccine websites. The study’s authors looked at tactics used by different websites. Fear of autism is a big theme, thanks to the now-discredited study, it found. Some websites even cast Wakefield as a victim. Those websites dismissed or excused the big problems with his report.

Other websites included vague appeals to readers’ values or emotions. Some sites argued for individual freedom of choice. Those arguments don’t mention that public health and safety laws protect everyone. Other websites fostered distrust of doctors and companies that make vaccines. They did not point out that parents will need both doctors and vaccines if children get sick. Still other sites suggested that vaccines were somehow toxic or not “natural.” They ignored the fact that preventable diseases are “natural” — yet can still be deadly.

“Unfortunately,” says Peter Hotez, “anti-vaccine misinformation media dominates the internet.” Hotez is a pediatrician and vaccine scientist in Houston. He works at Baylor College of Medicine and at Texas Children’s Hospital.

Bogus findings

Sometimes when scientists can’t replicate, or reproduce, another study’s findings, it’s because someone made a mistake. But Wakefield’s group didn’t just make mistakes, scientists would find. And the 1998 study wasn’t just false. It was “fraudulent,” editors of BMJ would later report.

In January 2010, a government panel in the United Kingdom announced that it had found many problems with the 1998 study. Wakefield, for example, had gotten money from lawyers involved in lawsuits against the companies that make vaccines. That’s considered a “conflict of interest.” Wakefield also was charged with picking and choosing data to show what he wanted. That reflected poor study design. Evidence also showed that the team had fudged data — changed them to make them say what Wakefield wanted. Beyond that, there were ethical problems with how Wakefield’s team had gotten data on the children.

Wakefield lost his medical license. And The Lancet retracted his group’s paper in February 2010. Scientific journals have since become more attentive to signs of potential fraud.

Yet the damage from Wakefield’s work continues. Many parents still refuse to vaccinate their children because of his team’s initial claims.

“I see your pain [and] your desire for answers to your children’s health problems,” said Washington State Secretary of Health John Wiesman. He made this comment as an aside to parents of children with autism during a March 5 congressional hearing in Washington, D.C. But the answer is not to refuse vaccines, Wiesman stressed.

In the end, says Hotez, there is no link between vaccines and autism. That complex brain condition starts during pregnancy — long before anyone gets vaccines, he notes.

Hotez wrote about many more studies confirming the lack of any vaccine link to autism in a 2018 book. It’s about own adult daughter, Rachel, who has autism. And the title sums up what all the studies show: Vaccines Did Not Cause Rachel’s Autism.

Power Words

(more about Power Words)

autism     (also known as autism spectrum disorders ) A set of developmental disorders that interfere with how certain parts of the brain develop. Affected regions of the brain control how people behave, interact and communicate with others and the world around them. Autism disorders can range from very mild to very severe. And even a fairly mild form can limit an individual’s ability to interact socially or communicate effectively.

colleague     Someone who works with another; a co-worker or team member.

conflict of interest     A situation where someone may have something to gain from (such as money, power or a job) by not making a fair or objective assessment of something. Journals, for instance, often ask the authors of journal papers to report any potential conflicts of interest that might affect their judgment of research data or conclusions as to their value.

data     Facts and/or statistics collected together for analysis but not necessarily organized in a way that gives them meaning.

develop     To emerge or come into being, either naturally or through human intervention, such as by manufacturing. (in biology) To grow as an organism from conception through adulthood, often undergoing changes in chemistry, size and sometimes even shape.

disorder     (in medicine) A condition where the body does not work appropriately, leading to what might be viewed as an illness. This term can sometimes be used interchangeably with disease.

ethics     (adj. ethical) A code of conduct for how people interact with others and their environment. To be ethical, people should treat others fairly, avoid cheating or dishonesty in any form and avoid taking or using more than their fair share of resources (which means, to avoid greed). Ethical behavior also would not put others at risk without alerting people to the dangers beforehand and having them choose to accept the potential risks. Experts who work in this field are known as ethicists.

fraud     To cheat; or the resulting effects of something done by cheating. Or to make a mistake and intentionally cover up the error.

internal medicine     A branch of medicine where doctors diagnose and treat adults for conditions that don’t need surgery. Doctors who work in this field are known as internists.

internet     An electronic communications network. It allows computers anywhere in the world to link into other networks to find information, download files and share data (including pictures).

journal     (in science) A publication in which scientists share their research findings with experts (and sometimes even the public). Some journals publish papers from all fields of science, technology, engineering and math, while others are specific to a single subject. The best journals are peer-reviewed: They send all submitted articles to outside experts to be read and critiqued. The goal, here, is to prevent the publication of mistakes, fraud or sloppy work.

link     A connection between two or more people or things.

measles     A highly contagious disease, typically striking children. Symptoms include a characteristic rash across the body, headaches, runny nose, and coughing. Some people also develop pinkeye, a swelling of the brain (which can cause brain damage) and pneumonia. Both of the latter two complications can lead to death. Fortunately, since the middle 1960s there has been a vaccine to dramatically cut the risk of infection.

media     (in the social sciences) A term for the ways information is delivered and shared within a society. It encompasses not only the traditional media — newspapers, magazines, radio and television — but also Internet- and smartphone-based outlets, such as blogs, Twitter, Facebook and more. The newer, digital media are sometimes referred to as social media. The singular form of this term is medium.

mumps     A highly contagious childhood viral disease characterized visually by swollen cheeks and a puffy jaw due a swelling of the salivary glands. It causes flu-like symptoms, including fever, muscle aches, headaches and being very tired. It’s spread as influenza is, by sneezing, coughing or touching something contaminated with the virus, such as a patient’s hands, drinking glass or spoon. In rare cases, the disease can inflame the brain, spinal cord or other tissues or cause deafness.

online     (n.) On the internet. (adj.) A term for what can be found or accessed on the internet.

pediatrician     A doctor who works in the field of medicine that has to do with children and especially child health. 

range     The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists.

replicate     (in biology) To copy something. When viruses make new copies of themselves — essentially reproducing — this process is called replication. (in experimentation) To copy an earlier test or experiment — often an earlier test performed by someone else — and get the same general result. Replication depends upon repeating every step of a test, one by one. If a repeated experiment generates the same result as in earlier trials, scientists view this as verifying that the initial result is reliable. If results differ, the initial findings may fall into doubt. Generally, a scientific finding is not fully accepted as being real or true without replication.

risk     The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)

rubella     A formerly common childhood infection sometimes called the “German” measles or three-day measles. The short-lived infection tends to cause a slight fever and rash that spreads from the face to the rest of the body. Almost half of infected people show no symptoms. The big risk is to the baby of women who get the disease during pregnancy. The child may develop deafness, vision problems, heart defects, mental retardation and liver or spleen damage.

symptom     A physical or mental indicator generally regarded to be characteristic of a disease. Sometimes a single symptom — especially a general one, such as fever or pain — can be a sign of any of many different types of injury or disease.

toxic     Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.

United Kingdom     Land encompassing the four “countries” of England, Scotland, Wales and Northern Ireland. More than 80 percent of the United Kingdom’s inhabitants live in England. Many people — including U.K. residents — argue whether the United Kingdom is a country or instead a confederation of four separate countries. The United Nations and most foreign governments treat the United Kingdom as a single nation.

vaccine     (v. vaccinate) A biological mixture that resembles a disease-causing agent. It is given to help the body create immunity to a particular disease. The injections used to administer most vaccines are known as vaccinations.


Journal: A. Hviid et al. Measles, mumps, rubella vaccination and autism: A nationwide cohort study. Annals of Internal Medicine. Vol. 170, March 5, 2019. doi: 10.7326/M18-2101.

Journal: S. Omer and I. Yildirim. Further evidence of MMR vaccine safety: Scientific and communications considerations. Annals of Internal Medicine. Vol. 170, March 5, 2019. doi: 10.7326/M19-0596.

Journal: The MMR vaccine is not associated with risk for autism. Annals of Internal Medicine. Vol. 170, March 5, 2019.

Hearing: United States Senate. Committee on Health, Education, Labor and Pensions. “Vaccines Save Lives: What Is Driving Preventable Disease Outbreaks?” Washington, D.C. March 5, 2019.

Book: P. Hotez. Vaccines Did Not Cause Rachel’s Autism. Johns Hopkins University Press. October 30, 2018. ISBN: 9781421426600.

Journal: M. Moran, et al. What makes anti-vaccine websites persuasive? A content analysis of techniques used by antivaccine websites to engender anti-vaccine sentimentJournal of Communication in Healthcare. Vol. 9, December 7, 2016, p. 151. doi: 10.1080/17538068.2016.1235531.

Journal: T.S. Rao and C. Andrade. The MMR vaccine and autism: Sensation, refutation, retraction, and fraudIndian Journal of Psychiatry. Vol. 53, April – June 2011, p. 95. doi: 10.4103/0019-5545.82529.

Journal: F. Godlee et al. Wakefield’s article linking MMR vaccine and autism was fraudulentBMJ. Vol. 342, Jan. 6, 2011, p. c7452. doi: 10.1136/bmj.c7452.

News article: B. Deer. How the case against the MMR vaccine was fixed. BMJ. Vol. 342, Jan. 6, 2011, p. c5347. doi: 10.1136/bmj.c5347.  https://www.bmj.com/content/342/bmj.c5347.