Vaccines photo

Voters heading to the booths during the 2016 primaries likely have a lot on their minds, from the economy to social issues. But there’s another matter they should consider: how well the candidates understand and respect science.

A candidate’s grasp of science isn’t just a matter of political rhetoric—it affects society. The failure to acknowledge climate change, for example, puts communities and economies at risk, such as when the government fails to reduce emissions or help prepare for extreme weather or sea-level rise. Misinformation also influences public opinion: Parents who heard presidential candidates make inaccurate statements about the safety of the HPV vaccine during a 2011 debate, according to a 2015 University of North Carolina study, were more likely to think the vaccine causes short-term health problems (though it didn’t affect their willingness to vaccinate).

Science isn’t partisan—it’s an organized process that tests ideas and ultimately builds a fact-based knowledge about the world around us. It’s self-correcting, and the truths it uncovers are apart from political influence. The electorate seems to recognize that: A 2015 study that looked at the responses of 2,000 registered voters found that most are happy to defer to science for public-policy issues, regardless of whether they’re Republican, Democrat, or Independent.

The trouble comes when science is misunderstood or deliberately misrepresented by those with a podium. We’ve seen that on both sides of the aisle: As recently as 2008, both Barack Obama and Hillary Clinton expressed suspicions that vaccines might cause autism (they don’t, and both politicians have changed their views on the matter).. In the run-up to this year’s election, the most questionable claims come from Republican candidates. “If you look at politicians today,” says Elizabeth Suhay, a political-behavior expert at American University, “it’s very clear that Republicans are being more irresponsible in statements about science.”

Here are six of the claims we’ve heard presidential candidates make, and what the science actually says.

Vaccines cause autism, and parents should be able to opt out of them or choose alternative schedules.
Vaccine vs. Autism fact check Popular Science

Science says:

The conspiracy theory regarding vaccines and autism largely began, unfortunately, in a scientific journal—specifically, a 1998 paper in The Lancet. The lead author was a British doctor named Andrew Wakefield, and the paper described eight children who supposedly showed signs of autism within a month of their measles-mumps-rubella (MMR) vaccine. The study lacked a control and used questionable methodologies, among other things, so The Lancet retracted it in 2010.

Since then, dozens of studies have explored various hypotheses on autism and vaccines. In a 2009 review paper of 20 of these studies, Jeffrey Gerber and Paul Offit—both pediatricians and infectious disease experts at the Children’s Hospital of Philadelphia—wrote: “Both epidemiological and biological studies fail to support these claims.” And a 2014 meta-analysis by researchers at the University of Sydney, which included data from more than 1.25 million children, concluded that there is no link between the MMR—or vaccination in general—and autism.

Yet throughout the primaries, presidential candidates—including Donald Trump, Chris Christie, and physicians Rand Paul and Ben Carson—have suggested that parents should be able to choose whether and how their children are vaccinated.

Delaying or altering vaccine schedules has no impact on whether a child develops autism when study after study shows there’s no link between the two. Yet another found this in 2015: Researchers analyzed medical data from 95,727 children, of whom 1,929 had older siblings with autism. The children with siblings with autism were less likely to receive the MMR vaccine than those without. Because autism has a strong genetic component, they were also more likely to eventually be diagnosed with the condition. The results showed that the unvaccinated children were no less likely to get autism than vaccinated ones.

On the other hand, failure to vaccinate comes with well-known risks. “By delaying or withholding vaccines, all you do is increase the period of time during which children are susceptible to these diseases,” Offit says. Infectious diseases such as pneumococcus, chicken pox, whooping cough, measles, and mumps all still persist in the United States, despite the fact that we’ve cut infection rates—through vaccination. Says Offit, “So a choice not to get a vaccine is a choice to take a very real risk of getting one of these diseases.”

Children shouldn't receive the HPV vaccine.
Should children get the HPV vaccine? Popular Science

Science says:

There are more than 100 strains of the human papilloma virus (HPV), and of those, around 40 are spread through sexual contact (although the virus can also pass from mother to child during a vaginal birth). Some of those strains can cause genital warts, while others might lead to cancer of the cervix, penis, anus, and throat.

The Centers for Disease Control and Prevention include the HPV vaccine in the standard series of childhood vaccinations. Both girls and boys should get the vaccine when they’re 11 or 12, the CDC says, although later vaccination is recommended for those who miss that window. Candidates like Carly Fiorina nonetheless balk at that advice. Says Fiorina: “A school district shouldn’t be able to say, ‘Sorry, your kid can’t come to school for a disease that’s not communicable, not contagious, and where there really isn’t any proof that [vaccinations] are necessary at this point.’”

The virus is communicable, of course. And the best time to get the HPV vaccine is well before children become sexually active—not after—so that they’re fully immunized, says Maria Trent, a pediatrician specializing in adolescent medicine and a researcher at Johns Hopkins Bloomberg School of Public Health. “It’s very important parents seriously consider all the vaccine series,” Trent says, “regardless of how [their children] might acquire the infections.”

Because HPV is so common—1 in 4 people in the U.S. has it—many people are infected around the time of their first sexual contact. And more than half of high school students in grades 9 through 12 have had sex. Some squeamishness seems to stem from the belief that the vaccine will encourage children to become sexually active earlier, but a 2013 paper from researchers at UCLA’s Center for Cancer Prevention and Control Research found that not to be true.

Scientists illegally purchase fetal tissue to conduct research.
What is being done with this fetal tissue? Popular Science

Science says:

Fetal tissue is rich with stem cells, which can be used to build different types of organs. Because these cells are so plastic, they are useful in a wide range of medical research, including understanding infectious diseases such as HIV, cancer, developmental disorders, and more. For example, researchers can use fetal stem cells to build a humanlike immune system in a mouse in order to study how pathogens attack us—without actually having them do so. In January 2016, 59 medical schools, professional societies, and research centers signed a public statement from the Association of American Medical Colleges underscoring the importance of fetal-tissue research.

Fetal tissue comes from voluntary donations by women who have had miscarriages or abortions. Despite the fact that some women want to give this tissue to science, it isn’t always easy for researchers to obtain. There are only so many organizations willing to get involved in what has become a controversial process. Comments this past fall from both Carly Fiorina and Ted Cruz make it no easier. Both candidates publicly questioned the fetal tissue donation process at Planned Parenthood—not the biggest supplier, but perhaps the most widely known. The statements were sparked by footage from anti-abortion activists who allege that it shows Planned Parenthood officials trying to sell fetal tissue illegally (last week, a grand jury in Texas cleared Planned Parenthood and indicted the video-makers on felony charges for tampering with government records and a misdemeanor for illegally trying to buy fetal tissue).

Planned Parenthood has programs for fetal-tissue donation in only two states, California and Washington. They used to ask for reimbursement for the cost of processing the materials, says Eric Ferrero, Planned Parenthood’s vice president of communications. This is legal, but the organization changed its policy this past September to absorb all costs associated with fetal-tissue donations.

Loss of any source of fetal stem cells is bad news for research. “There’s a real shortage of this tissue,” says one researcher who uses fetal tissue to study infectious diseases and who prefers to remain anonymous because of safety concerns (a common trend in this line of research). “In our lab, we’re always anxiously awaiting to see if we can get these tissues because it is so important in the work we do.”

Mental illness causes gun violence
What are the causes? Popular Science

Science says:

After mass shootings, politicians tend to blame mental illness, not gun laws. In fact, in this past year alone, candidates including Marco Rubio, Donald Trump, and Ben Carson have tried to link the two. On NBC last October, for example, after a mass shooting at an Oregon community college, Rubio said: “We have two issues in this country. One is mental illness, which we need to begin to address more seriously… And the other, of course, is why have we become so violent as individuals.”

But according to Jeffrey Swanson, a medical sociologist at the Duke University School of Medicine, only 4 percent of violent acts can be attributed to mental illness. And when you look specifically at violent acts involving guns, the National Center for Health Statistics found that people with mental illness were responsible for just 5 percent of gun-related killings between 2001 and 2010. It’s distorted to focus on mass shootings and mental health, says Swanson, because the usual perpetrator is highly atypical of those with mental illness. “The vast majority of them are not violent and never will be,” he says, “so you can’t generalize from one person.”

That’s not to say there’s no danger from the mentally ill interacting with weapons, but the real hazard is that they’ll harm themselves. According to a 2002 review by researchers at the World Health Organization, more than 90 percent of people who commit suicide have a diagnosable mental disorder. And a study that same year from the National Institute of Mental Health found that 1 in 5 suicide victims had contact with mental-health services in the month before their death.

Statistics do show that restricting access to guns can reduce suicides. According to multiple studies by the Harvard Injury Control Research Center, states with higher gun ownership have higher levels of firearm suicide. Countries that have decreased gun ownership have seen lower levels of suicide by guns, such as when Switzerland cut its civilian army in half—and took away their personal service weapons—in 2003.

Scientists thought Earth was cooling in the '70s, so they can't be trusted on global warming either.
Stances on climate change Popular Science

Science says:

In the 1960s and 1970s, researchers knew that various compounds in Earth’s atmosphere might contribute to climate change, but they weren’t sure which might have the biggest effect. For example, some scientists were realizing that greenhouse gases might heat things up, while others were looking at compounds called aerosols, which could scatter sunlight and cool the planet. A handful of research suggested the cooling effects might win out, including a much-cited 1971 Science paper by researchers at NASA’s Goddard Space Flight Center.

Science reporters liked the story of global cooling and boosted its signal in the media (including Popular Science in 1973). This might be why candidates such as Ted Cruz and Mike Huckabee still say that scientists broadly accepted global cooling. But science says otherwise. In 2008, Thomas Peterson, then at NOAA’s National Climatic Data Center, and colleagues published a review of the scientific literature from the 1970s and found there was actually a stronger consensus for global warming.

Global cooling’s brief stint was no match for today’s consensus on climate change, which includes, among other things, a 2013 report from the Intergovernmental Panel on Climate Change, which synthesizes 9,200 peer-reviewed studies. “There’s no real comparison between the two—it’s like saying that physics is wrong because we thought Earth was flat back in the day,” says Zeke Hausfather, a research scientist at Berkeley Earth who specializes in surface-temperature records. “Science advances through the collection of knowledge and testing of hypotheses. Just because some hypotheses in the past were wrong doesn’t necessarily cast doubt on our current understanding of scientific issues.”

Even if global warming exists, there's no proof of how much humans are to blame.
Placing the blame. Popular Science

Science says:

While both humans and natural phenomena influence climate change, the data suggests that we play a substantial role in warming the planet, says Ben Santer, an atmospheric scientist at Lawrence Livermore National Laboratory. While we don’t have “the luxury of a time machine” to measure how much the climate varied before humans entered the picture, says Santer, climate models can help tease out how much we’ve affected it since.

In a 2013 paper in the Proceedings of the National Academy of Sciences, Santer and colleagues looked at satellite data and climate models, and found a human “fingerprint” on global warming: changes in the atmosphere that couldn’t be solely explained by natural influences, such as fluctuations of the sun and volcanic eruptions. In a second paper that same year, they used 20 climate models to look at patterns in each layer of the atmosphere, and likewise found that humans played a role in warming. And in the 2013 IPCC report, hundreds more papers point to human influence too.

That hasn’t stopped candidates, such as Jeb Bush, from questioning humans’ role in climate change. “For the people to say the science is decided on this is just really arrogant,” he said at a New Hampshire campaign event in May 2015. “In my opinion, it’s arrogant to make ignorant comments about the science without any kind of understanding,” Santer says. “Scientists have been looking at these questions of causation—and trying to figure out the relative contributions—for decades. The best explanation of what we’ve observed has to involve a strong human effect on climate.”