They gave it a shot. Actually, several hundred million shots. But despite lofty goals set by the World Health Organization to eradicate measles in four of its six regions by 2015, the disease continues to sicken — and kill — children around the world.

That's not to say all the news is bad. Data just released by the World Health Organization show that between 2000 and 2014, the number of measles-related deaths plummeted from 546,800 to 114,900. But progress has slowed recently. Report author Dr. Robert Perry, a vaccine specialist, explained what needs to happen to make measles history. This conversation has been edited for length and clarity.

Why is measles such an important target?

It's one of these traditional children's diseases that used to affect every kid worldwide. It was a common cause of blindness. And the cells killed by measles leave people severely immunocompromised — the cells come back but without immunological memory. So kids get pneumonia and infections [and their bodies don't know how to fight them off].

There's a lot of stuff that isn't reported, so there are other effects we can't detect. When countries have done widespread vaccination, childhood mortality drops quite a bit. In areas that don't have vaccination, there are lots of kids that die.

What's caused this stagnation in progress?

This year, we're seeing the effects of money from Gavi [a global vaccine alliance that helped fund mass vaccination campaigns in 2014 that reached 221 million kids]. That's really knocked down cases this year. That's been one of the challenges until this year. These campaigns cost money, more than we like to think. We didn't have enough money, and countries couldn't come up with the funds. Supervision and planning couldn't be done. We get big numbers of kids immunized. But population figures are a chronic challenge and it's hard to tell whether a campaign was a success.

Are there any new strategies that seem promising?

It's maybe not so much new strategies but reinvigorating the monitoring, doing spot checks, going door-to-door to find out if kids are vaccinated. Doing good planning to get to hard to reach areas — renting a boat or a camel when necessary. One bottleneck now is that the vaccine is injected. We have to have people trained for that. It might be safer if it's a patch with thousands of microneedles on it. Just put the patch on the skin and the person gets the dose that way, and it can immunize them. We're hoping that will come online in two to three years. We'll be able to work in areas with real security challenges. It's hard to send teams into places like Syria. A patch vaccine might be a game changer.

How eager are people to get vaccinated? How big of a hurdle is aversion?

In many parts of the world, measles are dreaded. In those areas, people accept vaccines quite well. But in other parts of the world, there's more ambivalence. On a local level, there's a lot of work people are doing to develop communication strategies and put things in perspective. In Zimbabwe, [where fundamentalist religious sects opposed vaccination] it's pointing out the life-saving benefits. People were hiding their kids from vaccination teams. They were able to bring the kids down from the mountains. They were afraid of getting them immunized but by engaging with church leaders, telling them it's not forbidden and important for kids' health, they were able to counteract that. It's a real success story in that sense.

Any other success stories from the front lines?

The big success stories are in Southeast Asia in Bangladesh and Nepal. In Nepal, health care workers will hike for hours to get to remote villages. They are really committed and will walk distances people aren't expected to in other parts of the world. In Bangladesh, vaccines are seen as a fundamental right, and people will protest if they can't get them.

The report says "Measles can serve as an indicator of the strength and reach of the health system." So what else do these findings tell us?

Copyright 2016 NPR. To see more, visit http://www.npr.org/.