World health experts met recently to discuss an emerging global health crisis linked to the COVID-19 pandemic: plummeting rates of basic vaccinations among the world’s children.

While many experts have been acutely aware of the pandemic’s impact on essential health services, startling new immunization data from the World Health Organization and UNICEF indicate that decades of progress against some of the world’s most dangerous diseases is being severely threatened.

The numbers are stark. As scarce health resources have been rerouted to control COVID-19, children’s immunization rates have dropped to the lowest level since 2009. Last year, 23 million children missed out on basic vaccines through routine immunization programs, up 3.7 million from 2019. What’s more, 17 million children around the world are considered “zero-dose children,” meaning they have not received a single dose of lifesaving, routine vaccines — let alone a full immunization schedule.

That puts millions of children at risk of resurgent and deadly diseases like measles and polio, which are more life-threatening to children than COVID-19. And fewer vaccinated kids widens health equity gaps and increases the likelihood of outbreaks, which could push overstretched health systems to the brink of collapse.

A number of pandemic-related factors have contributed to this health setback. These include local health facilities allocating funds, equipment, and health care providers to COVID-19 response efforts rather than vaccine programs; citizens’ fear of COVID-19 transmission; and stringent local lockdowns.

The story is the same in regions across the globe. At the recent high-level political forum to address progress on the United Nations’ Sustainable Development Goals, officials from Afghanistan, Nigeria, and the Democratic Republic of the Congo spoke about the devastation COVID-19 has wrought on their local health systems and on the health of their nations’ children. India was hit especially hard: 3.5 million children there are unvaccinated or undervaccinated, the highest number of any nation in the world.

Countries cannot afford to lose decades of hard-fought progress, leaving children vulnerable to vaccine-preventable diseases even as the world races to distribute billions of COVID-19 shots through the joint COVAX effort. The implications would be catastrophic.

Read the full article about vaccine crises by Martha Rebour and Lori Sloate at United Nations Foundation.