“The measles vaccine is about 97% to 98% effective,” Fauci said.

Yet, recent outbreaks have indicated that vaccine misinformation is still an issue in the country, part of a movement by anti-vaxxers, who claim that vaccines do more harm than good. One notable figure behind this movement is environmental activist Robert F. Kennedy, Jr.

“I’m not anti-vaccine; I’m pro-science, I’m pro-safety,” Kennedy told Yahoo Finance. “I want people to be as safe as possible and I don’t want them to take a vaccine that could kill them. In many cases, the vaccines appear to be doing far more damage and causing far more deaths than the original disease was doing prior to the event of the introduction of the vaccine …. None of the 72 vaccines that are mandated have ever been tested for safety.”

That’s not an accurate assessment, however. The Food & Drug Administration (FDA) has a vaccine safety program in place. In order for the agency to approve a vaccine for public use, highly trained FDA scientists and doctors study the vaccine’s safety and effectiveness, and the FDA also inspects every vaccine manufacturing site.

One of Kennedy’s main arguments, and that of many other anti-vaxxers, is the supposed link between vaccines and autism. This was debunked 20 years ago, although it still runs rampant in anti-vaxxer communities. For his part, Kennedy contends that scientists have yet to prove that vaccines don’t cause autism.

“They don’t exist — no study that shows that vaccines don’t cause autism,” Kennedy said. “What the CDC says is not science.”

He believes that the CDC has a pro-pharmaceutical agenda and puts those needs ahead of the general public’s.

“Who do you believe?” Kennedy said. “The mom, who says, ‘My kid was completely healthy, I brought him in to get him vaccinated, and he got a brain injury and I checked around and there a million other kids like this.’ You think we should listen to that mom or we should say she's hysterical? Cause that's what the industry wants you to say, she's just hysterical.”

For his part, Fauci says, “This idea that [the CDC] has close ties with pharmaceutical companies is just not true.”

‘A dangerous game we play’

Before the vaccine was introduced in 1963, approximately 450 to 500 people died from measles each year in the U.S. Globally, there were over 2 million deaths a year before the vaccine.

“It’s a dangerous game we play,” Offit said. “I think that to ignore that [measles] is a serious disease is to ignore history.”

There were two major points in the last century that were deemed to be “vaccine scares.” In the 1980s, in the U.K., a group of parents claimed that the pertussis (whooping cough) vaccine had caused brain damage in their children. This created a scare so significant that vaccine rates plummeted until medical professionals were able to provide evidence that this was not actually the case.

Then, in the 1990s began the concerns that vaccines were linked to autism in children.

“In the late 1990s and early 2000s, the concern came from two different bases,” Dorit Reiss, a professor of law at the UC Hastings College of Law who focuses in legal issues around vaccines, said. “One, claims made from a British doctor [that] the MMR vaccine caused autism and two, claims made by several American parents that a preservative used in childhood vaccines then, hidrosol, a preservative that contains a metal mercury, was associated with autism.”

That doctor was Andrew Wakefield. He and his colleagues published a study alleging the connection in 1998, although the study was retracted in 2010.

According to the Children’s Hospital of Philadelphia, “this means that the paper is not part of the scientific record because it was found to be based on scientific misconduct. In this case, the studies were deemed fraudulent and data misrepresented.” Subsequent studies from others in the medical community found no link between the MMR vaccine and autism.

“Most claims have since been studied in millions of children, and both claims were shown untrue,” Reiss said. “But they created a scare that’s very hard to fight, even today, even after all the research was done.”

Social media doesn’t help — while it can disseminate important correct information, it also is often responsible for spreading false information.

“There’s a plus and a minus to the ready availability of information flow,” Fauci said. “But when something that’s incorrect gets into the social media and then goes viral, a certain percentage of people who read it are going to believe it even though it’s blatantly incorrect.”

As it stands, each state has some kind of law requiring specific vaccines for its students, but grants exemptions for medical reasons. 45 states and Washington, D.C. grant religious exemptions, and 15 states allow philosophical exemptions.

After measles broke out in Rockland County, New York, in October 2018, thousands of MMR vaccines were given out, mainly in the Orthodox Jewish community in the county where the outbreak was particularly prevalent.

Ed Day, the Rockland County Executive, is often skeptical of religious exemptions.

“If you truly have a religious objection to something, you would never do it,” he said.

“This was not religious objections per se,” Day added. “This was more fear, lack of record keeping, lack of insistence to stay with the law. That’s what the problem was and that’s why it was being corrected because from a variety of strategies, we were able to start seeing an uptick in the immunization rates, especially for our young people.”

‘It’s unfair to mandate without providing access’

Religious reasons and misinformation are not the only reasons why some people don’t get vaccinated. It can also be due to lack of health care access.

“Perhaps a child will be vulnerable until they go to school when they find out they really have to get vaccinated,” Fauci said. “As opposed to vaccinating the child at the time when they’re a young child, an infant, where you get your series of vaccinations within the first couple of years. If you don’t have access to a good health system, you’re not going to get vaccinated.”

Due to the Affordable Care Act (ACA), insurance coverage is mandated for childhood immunizations. For those who are uninsured, there are often federally funded health centers and state health departments that will give vaccines for free, or at low costs.

“Before you mandate vaccines, you need to solve access problems,” Reiss said. “You need to make sure the people can get the vaccine because it’s unfair to mandate without providing access.”

This is where the federal government can step up, she said.

“The federal government can do other things,” Reiss said. “For example, it can provide more money for education about vaccines. They can provide better support for vaccine clinics and other access, each access provisions. It can provide money for research on vaccine hesitancy to better develop ways to handle it.”

Until then, vaccine misinformation may very well remain throughout the country.

“The goal of a vaccine is to provide the immunity that is a consequence of natural infection without having to pay the price of natural infection,” Offit said. “Sadly, children have to suffer to get our attention … but it really shouldn’t come to that.”

According to WHO, nearly 20 million children in 2018 did not receive any measles vaccine — the organization attributes those figures to lack of access, conflict and displacement, and of course, misinformation.

“I just think we play a dangerous game … of Russian roulette and although there’s not five empty chambers and one bullet, maybe there was 100,000 empty chambers and one bullet,” Offit said, “but there’s a bullet in there and we better stop playing this game.”

Ignazio Monda contributed to this report.

Adriana is an associate editor for Yahoo Finance. Follow her on Twitter @adrianambells.

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