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A major new study offers yet more proof that MMR vaccine does not cause autism

The current study is now the largest one to have investigated the safety of the MMR vaccine, which makes its findings all the more powerful.

MMR vaccine
In the study, the vaccinated children had a slightly decreased risk of developing autism.
REUTERS/Rebecca Naden

A major, large study from Denmark has reconfirmed that children who receive the MMR vaccine, which protects against measles, mumps and rubella, are not at increased risk of autism.

Parents who refuse to have their children inoculated against those and other infectious diseases often do so out of a mistaken fear that vaccines cause autism.

That fear took off 20 years ago when a British doctor, Andrew Wakefield, published a paper in the medical journal Lancet that suggested a link between the MMR vaccine and autism. The paper has since been shown to be fraudulent, and Wakefield has been stripped of his medical license.

Yet, tragically, the paper has left its mark. The hesitancy or outright refusal of parents to have their children vaccinated has enabled vaccine-preventable diseases to make a comeback. The global incidence of measles, for example, jumped 30 percent in 2017, according to a report issued earlier this year by the World Health Organization (WHO).

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The situation is so serious that WHO has declared “vaccine hesitancy” one of the world’s top 10 health threats.

Here in the United States, where an effective vaccination campaign caused health officials to announce the elimination of measles in 2000, new outbreaks are once again occurring with disturbing regularity.

Last Friday, the Centers for Disease Control and Prevention (CDC) reported 47 more cases of measles in the U.S., increasing the total this year to 206. That compares to 372 cases in 2018, the highest number since 2014.

Study details

For the current study, which was published in the Annals of Internal Medicine, researchers looked at the health records of all 647,461 children born in Denmark between 1999 and 2010. The children were followed until they were an average of 8.6 years old.

Most of the children received the MMR vaccine, but 31,619 — about 5 percent — didn’t. The children’s health records also showed that 6,517 of the children (about 1 in 100) were diagnosed with autism, usually by the time they were 7 years old.

The researchers then compared the rates of autism among the MMR-vaccinated and unvaccinated children. They found no link between the MMR vaccine and an increased risk of autism. In fact, the vaccinated children had a slightly decreased risk of developing the developmental disorder.

The study’s findings were true even among subgroups of children who are at higher risk of developing autism, such as boys and children with a sibling with autism.

Nor did it matter whether or not the children had received other vaccines.

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“The study strongly supports that MMR vaccination does not increase the risk for autism, does not trigger autism in susceptible children, and is not associated with clustering of autism cases after vaccination,” the researchers concluded. (In his discredited paper, Wakefield had suggested that clusters of autism cases occur after the vaccine is given.)

Changing minds

This is an observational study, with the limitations that come with such studies. But a clinical trial — one that would randomly assign children to either receive or not receive the MMR vaccine — could never be done, as it would be unethical given the overwhelming evidence that the vaccine prevents disease and saves lives.

The current study is now the largest one to have investigated the safety of the MMR vaccine, which makes its findings all the more powerful. It’s far from being the first convincing study on this topic, however. Many others have also dispelled the myth that vaccination triggers autism, including a 2002 study by the same group of Danish researchers.

Yet, even though the evidence has never shown a link between MMR and autism, the new study was worth doing, argues an editorial that runs with the study.

“In an ideal world, vaccine safety research would be conducted only to evaluate scientifically grounded hypotheses, not in response to the conspiracy du jour,” write the editorial’s authors, epidemiologist Saad Omer and infectious disease specialist Dr. Inci Yildirim, both from Emory University in Atlanta, George. “In reality, hypotheses propagated by vaccine skeptics can affect public confidence in vaccines.”

Omer and Yildirim question, however, whether more studies are needed, given that we live in a “fact-resistant world” where data often fails to persuade — and where having any kind of discussion about the discredited link between MMR and autism can contribute to vaccine hesitancy.

“Generating evidence on MMR vaccine safety may be useful but is certainly not sufficient,” they write.

Omer and Yildirim say that doctors and public health officials need to clearly label the MMR-autism link a myth and then “focus on a few key facts.”

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“It is not essential to rebut every piece of misinformation,” they stress.

FMI: The study can be read in full at the Annals of Internal Medicine’s website. The research was funded by the Novo Nordisk Foundation and the Danish Ministry of Health.