We need 95 percent coverage to stop measles. We have 83.
In February 2024, the World Health Organization issued a sobering warning from Geneva: measles, a disease humanity once brought to the edge of eradication, is reasserting itself across the globe. More than 300,000 cases were recorded in 2023 — a 79 percent rise — as 51 nations faced major outbreaks, a consequence of vaccination coverage that, at 83 percent, falls well short of the 95 percent threshold the virus demands. The pandemic quietly undid years of immunization progress, and 142 million unvaccinated children now stand exposed to a disease that is both ancient and entirely preventable.
- Measles cases surged 79% in a single year, spreading across five of six WHO regions and signaling that a disease once nearing elimination has found new footing in the gaps left by pandemic disruption.
- The true scale of the crisis is likely worse than reported — deaths rose 43% in 2022 alone, and with cases climbing further through 2023, the WHO expects the final toll to be grimmer still.
- 142 million children have never received a measles vaccine, with nearly two-thirds living in low- and middle-income countries where outbreaks spread fastest and medical care is hardest to reach.
- The WHO is pressing countries to close the gap between 83% and 95% vaccination coverage — a formidable task requiring rebuilt trust, restored supply chains, and resources in health systems already stretched thin.
- The WHO projects that by the end of 2024, more than half of all countries will face high or very high outbreak risk, making this year a critical test of whether the world can outpace the virus.
In February 2024, the World Health Organization warned from Geneva that measles is spreading at a pace not seen in years. Natasha Crowcroft, the WHO's technical adviser on measles and rubella, reported more than 300,000 cases globally in 2023 — a 79 percent increase — with 51 countries experiencing major outbreaks, up from 32 the year before. The disease is now active in five of the WHO's six global regions. Only the Americas have held firm, though Crowcroft cautioned that may not last.
The reported numbers, she noted, almost certainly undercount reality. Deaths offer a starker measure: measles killed more than 130 people in 2022, a 43 percent rise, and the toll is expected to climb further as 2023 figures are finalized. Her assessment of 2024 was unsparing — the WHO projects that more than half of all countries will face high or very high outbreak risk before the year is out.
The cause is a vaccination gap that the pandemic made worse. Global measles vaccination coverage stands at 83 percent, far below the 95 percent needed to stop transmission of one of the most contagious diseases known. During COVID-19 lockdowns, routine immunization programs stalled worldwide, leaving a generation of children unprotected. An estimated 142 million children have never received the vaccine, 62 percent of them in low- and middle-income countries where outbreaks are hardest to contain.
Brazil's story captures both the fragility and the possibility at stake. The country achieved WHO measles elimination certification in 2016, only to see the virus return by 2018 and spread widely through 2019. Cases eventually fell from tens of thousands to just 44 in 2022, with the last confirmed case in June of that year — a recovery made possible only through sustained vaccination effort.
Measles spreads through the air and can cause pneumonia, encephalitis, and death, particularly in young children. Three effective vaccines exist and are available. The challenge now is deploying them fast enough and broadly enough to reach the children most at risk before the outbreaks Crowcroft and her colleagues see forming take hold.
The World Health Organization sounded an urgent alarm in February 2024: measles is spreading faster than it has in years, and the world is not prepared. Natasha Crowcroft, the WHO's technical adviser on measles and rubella, delivered the warning from Geneva with visible concern. More than 300,000 cases of measles were reported across 2023—a 79 percent jump from the year before. Fifty-one countries experienced major outbreaks, up from thirty-two the previous year. The disease is now circulating in five of the six regions the WHO monitors globally. Only the Americas have held the line so far, but Crowcroft made clear that reprieve may not last.
The numbers, she cautioned, are almost certainly lower than reality. Measles cases go unreported in many parts of the world, especially in countries with weaker health infrastructure. Deaths tell a starker story. In 2022 alone, measles killed more than 130 people—a 43 percent increase from the year before. As cases climbed through 2023, Crowcroft said the organization expects the death toll to rise again when final tallies are complete. She was blunt about what 2024 holds: "We know it will be a very challenging year." The WHO projects that by year's end, more than half of all countries will face either high or very high risk of measles outbreaks.
The root cause is not mysterious. It is vaccination. The global vaccination rate against measles stands at 83 percent—a number that sounds substantial until you understand what the virus demands. Measles is extraordinarily contagious. To stop it from spreading, health authorities need to vaccinate at least 95 percent of a population. The gap between 83 and 95 is where outbreaks live. That shortfall has real consequences. An estimated 142 million children worldwide have never received a measles vaccine. Sixty-two percent of them live in low- and middle-income countries, where the risk of outbreaks is highest and medical care is often hardest to reach.
The pandemic created a vaccination crisis that the world is still working through. During the COVID-19 lockdowns, millions of children missed their routine immunizations. Measles vaccination programs stalled. Health systems that were already stretched thin became overwhelmed. Now, years later, there is a generation of children who have no protection against a disease that can kill them. Crowcroft emphasized the scale of the challenge: vaccination coverage needs to rise from 83 to 95 percent globally. That is not a small adjustment. It requires reaching children in remote areas, rebuilding trust in vaccines after years of pandemic disruption, and securing resources in countries where health budgets are already thin.
Brazil's experience illustrates how quickly measles can return once vaccination falters. The country received WHO certification of measles elimination in 2016—a milestone that meant the virus had been eradicated from Brazilian territory. By 2018, it was back. The virus circulated freely through 2019, and Brazil lost its elimination status. Between 2018 and 2022, the country recorded 9,325 cases, then 20,901, then 8,100, then 676, then just 44. The last confirmed case appeared in Amapá state in June 2022. Brazil's trajectory shows both the fragility of elimination and the possibility of recovery—but only with sustained vaccination effort.
Measles itself is a serious disease. It spreads through the air when an infected person coughs, speaks, sneezes, or breathes near others. The first signs are high fever—above 38.5 degrees Celsius—followed by a dry cough, red eyes, a runny or stuffy nose, and a deep sense of malaise. Then comes the rash: red spots that spread across the body. In children under five, a fever that persists after the rash appears is a warning sign of severe disease. The virus can cause pneumonia, encephalitis, and death.
Three vaccines can prevent measles. The dupla viral protects against measles and rubella. The tríplice viral adds mumps to that protection. The tetra viral covers measles, mumps, rubella, and chickenpox. All are effective. All are available. The question now is whether the world can deploy them fast enough and widely enough to prevent the outbreak that Crowcroft and her colleagues see coming. The WHO's message is clear: 2024 will test whether countries can rebuild vaccination coverage before measles takes hold in the places where it has already begun to spread.
Citas Notables
We are extremely concerned about what is happening with measles— Natasha Crowcroft, WHO technical adviser on measles and rubella
We know 2024 will be a very challenging year— Natasha Crowcroft, WHO
La Conversación del Hearth Otra perspectiva de la historia
Why is 83 percent vaccination coverage not enough? That sounds like most people are protected.
Measles doesn't think in percentages. It spreads so fast that even small pockets of unvaccinated people create openings for it to move through a population. You need 95 percent to create what's called herd immunity—a wall so dense the virus can't find a path forward. At 83 percent, there are gaps everywhere.
So the 142 million unvaccinated children—are they concentrated in certain regions, or scattered?
Mostly concentrated. Sixty-two percent live in low- and middle-income countries where health systems are already fragile. That's where you see the worst outbreaks. But the virus doesn't respect borders. Cases in one region eventually reach another.
The source mentions the pandemic disrupted vaccination. How long does that kind of disruption take to recover from?
Years, usually. You don't just restart a vaccination program. You have to rebuild trust, retrain health workers, secure supply chains. And meanwhile, a whole cohort of children has grown up without protection. That's the generation at risk now.
Brazil lost its elimination status in 2019 but seems to have controlled it since. What changed?
Sustained effort. They went back to basics—vaccination campaigns, surveillance, quick response to cases. But it required political will and resources. Not every country can do that consistently, especially when other crises demand attention.
What does Crowcroft mean when she says the numbers are "underestimated"?
Many cases never get reported, especially in countries with weak disease surveillance. A child gets sick, recovers or dies, but no one reports it to health authorities. The true number of cases is probably much higher than 300,000.