This image depicts a schoolboy receiving a measles vaccination in1962. As part of the national immunization effort, this doctor was giving a measles vaccination to a young boy at Fernbank School in Atlanta, Georgia.

Cheryl Healton remembers the look on her mother's face when the then 8-year old was diagnosed with measles in 1961.

"I could tell by her reaction that my life was at risk," said Healton, now 66 and the dean of New York University's College of Global Public Health.

It was. While measles is best known for the rash it produces, the disease leaves people sick with a fever, runny nose, and can lead to complications like pneumonia, brain swelling and, in some cases, even death.

Nearly every American child contracted measles at some point before they turned 15 before a measles vaccine was introduced in 1963, according to the Centers for Disease Control and Prevention. About half a million new cases were reported to the CDC every year between 1942, the first year it was tracked, and 1962.

Most cases went unreported, and the CDC estimates up to 4 million people actually caught the measles every year. About 400 to 500 people died, 48,000 were hospitalized and 1,000 suffered encephalitis, or brain swelling.

That changed when the measles vaccine hit the market. Measles cases started plummeting. The first mumps vaccine was introduced in 1967 and the first rubella vaccine was introduced in 1969. In 1971, Merck launched the first combination measles, mumps and rubella vaccine.

A resurgence in the late 1980s and early 1990s led health officials to recommend babies get two doses of the measles, mumps and rubella shot instead of the previously recommended one. It also caused them to realize some children weren't getting vaccinated because they were uninsured or underinsured and they couldn't afford it, said Dr. Nancy Messonnier, acting director of the CDC's National Center for Preparedness and Response.

Lawmakers created the Vaccines for Children Program in 1993 that allows children who can't afford vaccines to get them for free. Seven years later, in 2000, the CDC declared measles eliminated from the U.S., meaning the disease was no longer being transmitted between Americans.

But people no longer saw the measles as a threat, and that was a problem. British physician Dr. Andrew Wakefield published a study in 1998 — which has since been retracted — that wrongfully claimed the MMR vaccine caused autism. His work is largely credited with giving birth to the so-called anti-vaxx movement that's scared some parents into refusing to vaccinate their children.

Eighteen studies from seven different countries on three different continents have since proven children who receive the vaccine are at no greater risk of getting autism, but the fear still exists, said Dr. Paul Offit, director of the Vaccine Education Center at the Children's Hospital of Philadelphia.

"It's hard to unscare people," he said. "It's easy to scare them. It's much harder to unscare them."

Messonnier said it's important people understand how "extensively and thoroughly" the MMR vaccine is studied.

Prevention efforts rely on herd immunity where most people in a community are vaccinated, creating a "societal cushion" that protects people who cannot be vaccinated, she said. When that breaks down, measles can spread quickly and easily. The disease is among the most contagious in the world, and it's still common in some parts of the world.

An estimated 7 million people were affected by the measles in 2016, according to the World Health Organization. Global measles deaths decreased 84%, dropping to 89,780 in 2016 from 550,100 in 2000.

Measles has started to spread again in recent years as more parents refuse to vaccinate their children, even though health officials stress immunizations are the best way to protect against the measles. The WHO reported a 300% increase in measles cases in the first three months of this year compared with the same time last year.

This year, health officials are battling the worst year for the disease in 25 years after unvaccinated Americans brought the disease back after visiting the Philippines, Ukraine and Israel, among other countries. The CDC has confirmed 940 new cases of measles so far this year through Friday, largely in unvaccinated children.

"What [this year's increase in cases] shows us is that our ability to control measles is fragile," Messonnier said.

Yet it's possible to eliminate measles "from the face of this Earth" because the MMR vaccine "is good enough to do that," Offit said. Two doses of the vaccine are 97% effective, according to the CDC.

For those in public health who have watched measles cases plummet over the years, watching it make a comeback is shocking.

"If you would have told me five years ago I would have laughed and said that's not possible," said Healton. "But the internet has made it possible."

Correction: A measles vaccine was introduced in 1963. An earlier version misstated the type of vaccine.