A massive new study from Denmark found no association between being vaccinated against measles, mumps, and rubella and developing autism.

In science and public health circles, that issue has long since been considered settled, with multiple studies over many years discounting the findings of a small study published more than 20 years ago that has since been expunged from the medical literature.

But the size of this study — involving 657,461 Danish children born between 1999 and 2010 — should, in theory, bolster the argument that doctors and public health professionals still find themselves forced to make in the face of entrenched and growing resistance to vaccination in some quarters.

The work, published Monday in the Annals of Internal Medicine, was conducted by researchers at the Statens Serum Institut in Copenhagen. Some of the same scientists published an earlier article on this topic in the New England Journal of Medicine in 2002, based on data from 537,303 Danish children born between 1991 and 1998.

Why redo the work? Because the misplaced concern hasn't gone away, said Anders Hviid, one of the researchers involved in the study.

"The idea that vaccines cause autism is still going around. And the anti-vaxx movement, if anything, has perhaps only grown stronger over the last 15 years," he told STAT. "The trend that we're seeing is worrying."

Measles cases are spiking around the globe

Six measles outbreaks are currently ongoing in the United States, with 206 cases reported in January and February, according to the Centers for Disease Control and Prevention. That two-month total is higher than the entire year's tally for 2017.

Measles outbreaks have also been reported in a number of other countries around the world. A French family with unvaccinated children recently brought the virus to Costa Rica. An outbreak in an Orthodox Jewish community in New York City was triggered by a case that contracted the virus in Israel. The World Health Organization's European regional office reported there were more than 85,000 cases across the continent in 2018 and 72 measles deaths.

Washington state has spent more than $1.2 million trying to contain an outbreak there that to date has seen 71 people become infected. State Health Secretary John Wiesman is appearing Tuesday before the Senate's Committee on Health, Education, Labor, and Pensions to ask for more funding to help the country's public health sector cope.

Among the things he plans to ask for: a 22% increase in funding for the CDC and a national information campaign to explain the value of vaccines.

The money is needed, he said, to ensure that "as the anti-vaccine movement has become so well organized, we are just really adequately prepared in getting out our message and to counter that."

But will another study discounting a link between the MMR vaccine and autism make a difference? Not everyone is so sure.

It's hard to convince a "fact-resistant" minority to vaccinate

In an editorial published with the study, Dr. Saad Omer of Emory University noted it's important to think about opportunity costs when deciding to devote research time and money to further exploring such a well-mined issue, writing that "continuing to evaluate the MMR-autism hypothesis might come at the expense of not pursuing some of the more promising leads."

(In an interview, Omer said he didn't object to this particular study, which used existing data as opposed to data that had to be newly collected.)

He also wrote that evidence hasn't won over the skeptics so far. "It has been said that we now live in a 'fact-resistant' world where data have limited persuasive value," he said.

In this August 1963 photo, a technician working under sterile conditions stores trays of living cell tissue in an incubator at the virus laboratories of Chas. Pfizer & Co. in Terre Haute, Indiana. Cells are nurtured to serve as hosts for live virus needed for the measles vaccine. AP Photo

But Hviid said the size of this study allowed his group to look at some additional claims that are made about MMR vaccine — for example that children considered "at risk" of developing autism might be more likely to be diagnosed with the condition if they receive the vaccine. That argument is sometimes made about children who have a sibling with autism.

The Danish data, drawn from a national health registry, showed no increase in autism in this subset of children. Nor did it see an onset of autism symptoms clustered around the timing of the MMR vaccine receipt.

"We found no support for the hypothesis of increased risk for autism after MMR vaccination in … Danish children; no support for the hypothesis of MMR vaccination triggering autism in susceptible subgroups characterized by environmental and familial risk factors; and no support for a clustering of autism cases in specific time periods after MMR vaccination," Hviid and his co-authors wrote.

Omer said the focus now needs to be on studies that make clear how best to persuade vaccine-hesitant parents that the vaccines are safe and in their children's best interest. Progress is being made on figuring out how to effectively communicate with such parents, he said, noting they make up a larger group than the more vocal individuals who flatly reject vaccines.

"It's an active area of research. But there are a lot of promising techniques that are coming online," Omer said.