This year, the U.S. has seen the highest number of measles cases since the disease was eliminated from the country in 2000.

There have been 175 cases reported in the U.S. so far in 2013, three times as many as in any year since 2000. Dr. Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention (CDC), said Thursday that the number was far too high 50 years after the measles vaccine was developed.

“The disease is remarkably infectious, but the vaccine is remarkably effective,” Frieden said at a press conference.

Read More About How the Anti-Vaccination Movement Has Fueled a Deadly Year »

Vaccination experts spoke with reporters about the latest measles activity, and noted that a lack of vaccination is fueling the rise in preventable disease.

In a new editorial in the journal JAMA Pediatrics, Dr. Kristen Feemster and Dr. Paul Offit cite 2000-2011 data retrieved from the CDC's Vaccine Safety Datalink, which showed that 48.7 percent of children were under-vaccinated prior to their second birthday, and that one in eight were under-vaccinated “owing to parental choice to delay or refuse certain vaccines.”

The vaccination debate received more fuel this week after journalist and talk show host Katie Couric aired a segment about Gardasil, an HPV vaccine, and interviewed two mothers who claim that their children were harmed because of vaccination. 

A new study published in JAMA Pediatrics indicates that improved education for parents and health care professionals is essential to underscore the importance of vaccinating adolescents against HPV before they become sexually active.

Experts: Reluctance to Vaccinate Continues to Hurt Global Health

With vaccination against measles now readily available across the U.S., the disease is considered eliminated. However, cases still travel into the country, especially from Western Europe, which experiences 25,000 cases a year. U.S. experts say that its prevalence there is also driven by a hesitancy to vaccinate children.

Ninety percent of this year’s measles cases, experts said, can be attributed to vaccine refusal, whether for religious or personal reasons. This year, there have been nine measles outbreaks in the U.S., centered in New York, North Carolina, and Texas.

The Texas outbreak was linked to Eagle Mountain International Church in North Texas, which encouraged its followers to avoid vaccinations. After a member returned from an overseas mission trip, 21 church members came down with measles. 

Dr. Samuel Katz, chairman emeritus of pediatrics at Duke University School of Medicine and co-developer of the measles vaccine, said parents who don’t vaccinate their children for personal beliefs may never come around.

“I don’t think we’re ever going to change their minds,” he said. “These are people who are very rigid in their ways.”

Luckily, it only takes about 95 percent of the population to be vaccinated for “herd immunity” to kick in and prevent major outbreaks.

Measles Still a Major Concern Worldwide

Dr. Alan Hinman, director for programs at the Center for Vaccine Equity, said that before the vaccine was available, there were about two million cases of measles worldwide annually, with 450 to 500 children succumbing to the disease each year. 

“It’s really nice to be worrying about 175 cases (in the U.S.),” he said. “It’s a nice milestone, but it shows we have a long way to go.” 

While the U.S. is still dealing with smaller outbreaks, the problems are far more severe in other parts of the world. Measles remains prevalent in parts of Eastern Europe, along with Nigeria, Pakistan, and Afghanistan.

Katz personally saluted “those in the trenches doing the work” getting vaccines out to the public, including the vaccination workers recently assassinated in northern Nigeria.

“Creating a vaccine is very exciting and fulfilling, but if it sits in a vile in a closet, it doesn’t do much good,” he said.