The World Health Organization recently announced that New Zealand and the Republic of Korea have become the first countries in the Western Pacific region to have eliminated both measles and rubella.

Both diseases can cripple communities, with rubella in pregnant women leading to severe birth defects in infants like blindness, deafness, and heart disease, and measles continuing to be one of the leading causes of death in children, killing 15 people every hour.

This milestone achievement in the fight against dangerous preventable diseases highlights the effectiveness of strong routine immunization programs, according to Dr. Shin Young-soo, WHO regional director for the Western Pacific, who spoke at the 68th session of the World Health Organization Regional Committee for the Western Pacific last week.

To be certified as measles and rubella free, regions must be able to show that endemic viral transmission has been interrupted for at least 36 months, and that verified surveillance measures are in place.

Read More: The UK Has Eliminated Measles for the First Time

Other countries in the region, including Australia, Brunei Darussalam, Cambodia, Japan, Hong Kong, and Macau have previously been declared measles free, but the eradication of both measles and rubella has never been accomplished before in the Western Pacific. Recently, the measles and rubella vaccinations have been combined, meaning that the fight to eliminate the diseases has also been joined.

Following this latest announcement, representatives of the region’s member states discussed and endorsed the proposed regional strategy and action plan for eliminating measles and rubella in the Western Pacific, but noted that, in spite of the progress that has been made, the path to eliminating these diseases from the region faces obstacles.

Papua New Guinea, for example, is currently in the midst of a dangerous outbreak.

“We are one of the countries in the region that is yet to eliminate measles and rubella,” the representative for the country said during the event. “Maybe we are one of the nations that could be categorized as not on track. That is pretty serious. Our immunization coverage has not been improved for decades. We have had immunization coverage at around 60 percent for a decade.”

Many other immunization gaps persist in the region, and people living in poor, remote regions are most likely to be affected by limited or non-existent access to vaccines and health services. Therefore, not only are these vulnerable groups the least likely to be protected from and the most likely to contract the diseases, they are also the least likely to receive appropriate treatment, according to WHO.

Read More: 1 in 10 Children Worldwide Left Without Life-Saving Vaccines in 2016

However, these immunization coverage gaps are now expanding beyond the poorest communities and into well-educated urban populations as well. For example, with anti-vaccination movements gaining traction in Malaysia, the country saw an unprecedented rise in the incidence of measles. The majority of patients affected in Malaysia were children under 15 whose parents opted against vaccination.

These movements have growing support throughout the region, and in recent years social media has effectively turned up the volume on the misinformation broadcast by the anti-vaxxer movement. Just this year, an unvaccinated traveler returned to Australia and prompted the first outbreak of measles to occur in the country since 2012.

In response to waning public confidence in immunization, the Australian government has introduced a variety of public health campaigns, including an education campaign to help families “Get the Facts about Immunization.” To that end, the representative for Malaysia also emphasised the need for better public education to defuse distrust and dispel myths about vaccines, urging the World Health Organization to take the lead on this.

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Regardless of the specific actions that need to be taken, it is clear that increasing and maintaining immunization coverage in the Western Pacific region is essential for reducing the risk of future outbreaks. Even once a disease has been eliminated from a country, it is still be able to re-emerge in areas if it remains active in other parts of the world.

Mark Jacobs, WHO’s director for the division of communicable diseases explained that, “what we mean by elimination is not that there is no disease, just that it stops circulation. When the United States eliminated measles, they explained it as: ‘measles doesn’t live here anymore, but it does visit.’”

These unwelcome visits are made all the more likely by low levels of immunization coverage and poor disease surveillance mechanisms. As such, “when it comes to immunization, the aim is to leave no one behind,” Jacobs continued.

Yet, Jacobs believes that the Western Pacific region faces multiple challenges when it comes to achieving this goal.

“For countries such as China, the size of the country creates a problem of universal vaccination coverage,” he said. “For a smaller country like PNG, it is an issue of geography, resourcing the health systems, making sure vaccination can reach population at the right temperature and surveillance systems can identify outbreaks.”

Despite these challenges however, this week’s announcement serves as an important reminder that immunization is the key to progress. Hopefully, this moment of celebration will encourage all member states to keep pushing forward in their efforts of ensuring that all 1.9 billion people living in the Western Pacific region can have happy, healthy lives protected from disease!

Global Citizen campaigns on the Global Goals, which call for universal access to vaccines and health services that protect against infectious outbreaks. You can take action on this issue here