Vaccination and autism
Is there a connection?
More than 20 years ago, a study was published in the Lancet journal, which claimed that there is a direct link between vaccination and autism. Parents sounded the alarm, an anti-vaccination movement appeared. Over time, the results of that work have been refuted, but the number of opponents of vaccinations is growing. The editors of Naked Science tried to understand the reasons for the growth of the anti-vaccination community and the link between vaccines and autism.
How do people have such confidence in the connection between vaccinations and autism
People who oppose vaccination are a small but vocal group who disagree with the general scientific opinion that vaccines are safe and do not lead to the development of autism. Most representatives of this camp do not care that more than ten studies have reached a dead end in the search for a supposed connection between the two phenomena. How can this be? How can people deny scientific data? It's all about the so–called Dunning–Kruger effect - a cognitive distortion that explains anti-vaccination moods.
The Dunning–Kruger effect, proposed by David Dunning and Justin Kruger in 1999, describes a situation in which people with extremely little information on a topic are confident that they know significantly more specialists. One of the founders of the concept of this effect, David Dunning, explained it this way: "The area of ignorance of people is often invisible to them."
In 2018, a team of researchers led by Dr. Matt Mott from the Annenberg Center for Public Policy at the University of Pennsylvania conducted a survey and found that people who know little about autism, do not have knowledge of basic facts and tend to believe misinformation, thought they knew more specialists. This self-confidence leads to the fact that some do not support the policy of mandatory vaccination and show skepticism towards doctors.
1,310 people took part in the survey. Dr. Mott's team found that 36% of respondents believed they knew more doctors, and 34% claimed to be aware of the possible causes of autism. The greatest degree of self-confidence was observed in those who had the lowest level of knowledge and the highest tendencies to maintain disinformation. These same people showed a predisposition to support non–specialists – like various celebrities - involved in the development of a political course.
Many people believe that anti-vaccination moods do not pose any danger, but scientific studies like the one described above show that they affect the real world. So, communities that oppose vaccination are steadily multiplying. And there is nothing surprising in the fact that they are in the greatest risk zone of infection with viruses from which they refuse to be vaccinated. It is even worth remembering the outbreak of measles in late 2018 – early 2019.
In 2018, Dr. Peter Hotez of the National School of Tropical Medicine at Baylor College of Medicine conducted a study in which scientists revealed an increase in the number of exemptions from vaccination for non-medical reasons in 12 of the 18 states where such a practice is allowed.
"In recent years, the social movement against vaccination has been growing in the United States; as a result, measles outbreaks have become more frequent," Hotez and colleagues said at the time.
Back in mid-2018, Hotez's research team noted that an increase in opposition to vaccination would also be followed by more outbreaks of diseases.
Nevertheless, anti-vaccination communities continue to grow and repeat like a mantra or a spell that vaccines provoke the development of autism.
The 2015 study and the dead-end shift
In 2015, an article appeared in the Journal of the American Medical Association about a large-scale study at that time, the purpose of which was to confirm or deny the connection of the MMR vaccine (a combined vaccine against measles, mumps and rubella) with the occurrence of autism (the study report itself can be found at the link.
The work carried out by Dr. Anjali Jain and her colleagues examined the medical histories of 95 thousand children, among whom were 15,000 unvaccinated aged two to five years, as well as about two thousand children already at high risk of developing autism.
As in previous similar studies, scientists have not found a link between the MMR vaccine and the risk of developing autism spectrum disorder (ASD). This turned out to be applicable to almost two thousand children at high risk of developing autism.
"Consistent with studies of other populations, we did not observe an association between the MMR vaccine and an increased risk of ASD," the authors wrote. "We also found no evidence that receiving one or two doses of the MMR vaccine was associated with an increased risk of ASD among children who have older siblings with ASD."
The analysis examined autism rates and MMR vaccines among children aged two to five years. The researchers did not identify an increased risk of developing autism due to immunization at any of these ages. Moreover, the number of cases of autism among vaccinated groups was lower. But, as the scientists noted, this may be due to the fact that parents, noticing early signs of autism, could postpone vaccination or refuse it altogether.
It is important to note that studies have been conducted over the years, during which attempts have been made to identify a causal relationship between the MMR vaccine and autism. Each time the samples increased, but no connection was established. In 1998, a study by Dr. Andrew Wakefield and his colleagues appeared in the Lancet journal, which claimed the opposite: there is a direct link between vaccination and autism (the work can be found at the link.
As of today, this study has been refuted and withdrawn from the journal. If you follow the link, you will notice a large inscription in red letters on the background of the text: "RETRACTED". It is not surprising that such a high-profile article aroused the interest of other specialists, and they, in turn, decided to conduct their own research. As already mentioned, it was not possible to find confirmations of the described data. However, the speculation surrounding this issue to this day gives many people concern. Many become "victims" of the Dunning–Kruger effect. It can also be assumed that it was these unrest that caused the decline in the number of vaccinations among families in which the eldest child suffers from autism – at least this is what the authors of the 2015 study suggest. Following Dr. Wakefield's article, many other articles were withdrawn, which talked about the discovery of a link between vaccination and autism.
Anyway, in 2015, Dr. Jain's work showed that among families without children suffering from autism, 84% of children aged two years and 92% of children under the age of five were vaccinated. In families where the eldest child suffered from autism, vaccination cases were significantly lower: 73% of children from two years old and 86% of children under five years old.
Danish Research 2018 – a new frontier
Measles was eliminated in the States in 2000. In 2010, the World Health Organization approved a strategy for the global elimination of measles by 2015. It was ambitious and, as it seemed, quite feasible.
By the beginning of 2019, 206 cases of measles had been reported in 11 states in the United States. In the EU countries, 82,596 cases of measles were reported from January to December 2018. The return of the disease is directly related to parents who increasingly refused to vaccinate their children with the MMR vaccine. This, of course, does not play into the hands of parents who vaccinated children in an attempt to protect them from such infectious diseases as measles, rubella and mumps. The anti-vaccination movement as a whole is based on Dr. Wakefield's research, which has already been mentioned above. It was he who first linked vaccination with the increasing number of cases of autism in children. Despite the fact that his research was refuted by 2010, the widespread confidence in Wakefield's statements turned out to be incredibly stable.
On the fifth of March this year, the latest study on this issue was published in the journal Annals of Internal Medicine. It is based on data collected over ten years from half a million people. However, it should be noted that, despite the unprecedented large-scale sample, anti-vaccinators, guided mostly by paranoia, shifting blame to others, distrust of specialists and even just stubbornness, are unlikely to consider this a significant proof to refute beliefs.
The study was conducted by scientists from the Statens Serum Institute in Denmark. In the course of it, there was no statistical relationship between receiving the vaccine and the possible development of autism (the work is available at the link. There was also no connection between the areas in which vaccines are used and those associated with the development of autism. Moreover, with the growth of the anti-vaccination community, cases of autism have also become more frequent. So, in 2016, autism was observed in one eight-year–old child out of 68 children, and in 2018 - in one of 59.
The researchers studied the medical histories of Danish children born between 1999 and 2010. Using the population registry, scientists assessed other risk factors, including cases of autism among siblings, as in the 2015 study, and thoroughly investigated the alleged relationship between vaccination and the development of autism. Discussing the statistics presented in the study, health expert Saad Omer stated in an interview for the Washington Post: "The correct interpretation is that there is no connection at all."
However, the same Omer and a number of other experts believe that, despite all the evidence presented in the Danish study, spending research funds on persuading anti–vaccinators is a dubious idea. Bioethicist Sid M. Johnson commented: "They are immune to facts." Almost simultaneously with the study, an editorial was published in the Annals of Internal Medicine Omer, in which he decries the waste of time, effort and money on people living in a world "resistant to facts."
Omer and other experts are concerned that the beliefs of anti-vaccinators undermine public confidence in vaccines, and believes that the financial costs of collecting evidence to the contrary are justified only if the cost of such research is not too high. He also noted that this money can be spent in an alternative way, namely, on the development of medicines.
The publication of this study almost perfectly coincided with a hearing in the US Senate, at which 18-year-old Ethan Lindenberger testified about his decision to get vaccinated against the wishes of his parents. Earlier, Lindenberger wrote on the Reddit website that after reading the Facebook posts, his mother became convinced that vaccines were "some kind of government scheme." In his post, he writes: "In a few weeks, I am scheduled to receive injections! My mom was very angry, but dad said that since I'm already 18, he doesn't really care. Despite the fact that my mom is trying to convince me not to do it and says that I don't care about her, I know that I just need to do it, no matter what."
In turn, Facebook said it was taking the necessary steps to limit the spread of health-related misinformation. Already on March 6, the company announced a new plan, in which all advertising posts containing false information about vaccines will be blocked, and over time, advertising accounts of pages that continue to violate the rules of the network will be blocked.
The situation for today
The desire of anti-vaccination parents to control their children's decisions regarding their health is logical, but unfortunately for them, their children – as well as other children with whom they may come into contact – are not immune to infectious diseases.
As a result, all other people have no choice but to sit and watch for the possible return of serious diseases. So, today many states in the United States allow a "religious" refusal, allowing parents to refuse to vaccinate their children, but, as statistics indicate, this problem is not only in the United States. Due to the increase in the number of measles cases, WHO classifies "vaccination insecurity" as one of the ten most serious threats to global health in 2019, which could lead to the death of 1.5 million people annually.
In an article by Dr. Omer, already mentioned earlier, he, as a public health researcher from Emory University, and Dr. Inchi Yildirim from Emory Medical School note: despite the fact that enough time has passed since the publication of a small study that provoked mass hysteria about the alleged link between vaccines and autism, researchers continue to use resources for research aimed at refuting that work.
"In an ideal world, research on the safety of vaccines would be conducted only to evaluate scientifically based hypotheses, and not in response to a conspiracy," they write in their article.
In the same article, scientists argue that doctors and other representatives of public health should firmly call this connection a "myth".
Dr. Sean O'Leary, a representative of the American Academy of Pediatrics, associate professor of the Faculty of Pediatrics at the University of Colorado at Denver, spoke on the same topic. He noted that refuting a myth can be a difficult task and that every time someone repeats it, there is a risk of strengthening it.
"All parents will remember from your complicated explanation of why vaccines don't cause autism is that they are somehow related," says O'Leary. "Therefore, pediatricians should focus on the diseases that we are trying to prevent, and if you need to mention any myth, you should definitely note that it is exactly what it is."
Dr. O'Leary also noted that doctors working with parents need to have factual and accurate information for those who want to take a deeper look at this issue, since due to background information noise in the media and, in particular, social networks, it can be difficult for modern parents to distinguish truth from fiction.
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