Childhood vaccinations are stagnating in around twenty wealthy countries, and serious diseases are resurfacing.

In a couple of days, it will be 10 years since a death that shook consciences in Spain, due to its unique and preventable nature: a six-year-old boy from Olot (Girona) died of diphtheria, a serious infectious disease that is preventable with a vaccine. This child's death, who was not vaccinated by his parents' decision, was the first case recorded in the country since 1987 and sparked a public debate about the impact of vaccination. His story crystallized the risks of embracing anti-vaccine movements and demonstrated that even in Spain, with high childhood immunization rates, one cannot take everything for granted and let one's guard down. "I had a terrible time. It seemed absurd to me that this would happen in the 21st century. It was dramatic, but the evidence of the case moved many consciences, and some people changed their minds," recalls Boi Ruiz, then Minister of Health of the Catalan Government.

The case of the child who died of diphtheria reminded even the most forgetful of how some diseases, once widely believed to be eradicated, can loom large. It also demonstrated that they can return, even in high-income countries, as soon as a strategy as effective as routine vaccination is abandoned. A warning that, a decade later, has been brought back to the fore by research published this Tuesday in The Lancet . The study warns that progress in childhood vaccination coverage has stagnated or even reversed. Although developing areas are the hardest hit, with lower coverage rates and less access to vaccines, this trend has also been seen in some twenty wealthy countries, including Spain. The most direct consequence of this halt, the authors explain, is the emergence of new and increasingly frequent outbreaks of preventable diseases, such as diphtheria, polio, and measles.

Looking back, the last half-century is a living example of the life-saving power of vaccines: between 1980 and 2023, vaccination coverage against diseases such as polio, measles, diphtheria, tetanus, and whooping cough doubled; and the number of unvaccinated children worldwide fell by 75% (from 58.8 million to 14.7 million in 2019). However, the study, which includes data from 200 countries, also reveals that progress in immunization campaigns has slowed over the past two decades: between 2010 and 2019, measles vaccination fell in almost half of the countries analyzed, and in 21 of 36 wealthy countries, declines in coverage of at least one dose of the vaccine against diphtheria, tetanus, whooping cough, measles, polio, or tuberculosis were also detected.

“We are at a crossroads ,” explains Quique Bassat, director general of ISGlobal and co-author of this research. The situation is not catastrophic, he clarifies, because high coverage is being achieved, but the goals for 2030—to halve the number of unvaccinated children and achieve 90% coverage—are ambitious, and the world is “stuck in that final burst of momentum.” The article's conclusions, he points out, are “a warning to everyone.” “We have to be alert. In the world of vaccines, when you don't meet your goals, it shows because we see measles outbreaks around the world, the resurgence of diphtheria, and also cases of polio, a disease we haven't been able to fully eradicate. Either we get our act together, or we won't just not make progress, we could even regress,” he concedes.

The World Health Organization's (WHO) vaccination program, launched in the mid-1970s, is estimated to have prevented 154 million deaths worldwide, but "progress has not been universal," warns Jonathan Mosser, lead author of the study and a researcher at the Institute for Health Metrics and Evaluation at the University of Washington (USA), in a statement. In fact, half of the world's unvaccinated children are concentrated in just eight countries: Nigeria, India, the Democratic Republic of the Congo, Ethiopia, Somalia, Sudan, Indonesia, and Brazil. "Routine childhood vaccination is among the most effective and cost-effective public health interventions available, but persistent global inequalities, challenges stemming from the COVID pandemic, and rising misinformation and vaccine hesitancy have contributed to slowing immunization progress. These trends increase the risk of outbreaks of preventable diseases," he warns.

Polio in Pakistan, measles in Europe

These are not empty words. There are increasing numbers of polio cases in Pakistan and Afghanistan; an ongoing outbreak in Papua New Guinea, where half the population is unimmunized; and a resurgence of diphtheria has also been reported, with outbreaks in Bangladesh, Nepal, Nigeria, Pakistan, Venezuela, and Yemen. Cases of whooping cough and measles have also skyrocketed in Mexico.

Developing countries, where weak health systems intersect with large birth cohorts, geographic isolation, exposure to conflict, and a loss of trust in vaccines, are bearing the brunt of the cessation of vaccination, but this resurgence of preventable diseases is also being observed in the West. In 2024, measles infections recorded in Europe increased tenfold—the number of reported cases was the highest since 1997. And in the United States, an outbreak of the disease, which has spread to some thirty states, has already recorded more than 1,000 cases by May 2025, surpassing the total number of measles infections reported for the entire previous year. “Measles is an excellent indicator of how things are going with vaccination coverage,” Bassat says. As soon as immunization rates drop, outbreaks resurge. The first measles-related death in the U.S. in the last decade occurred in an unvaccinated child as part of an outbreak in Texas in early 2025.

Spain is on the list of 21 wealthy countries (Japan, Italy, Sweden, the United Kingdom, Germany, and France are also included) where the increase in vaccination coverage against some preventable diseases slowed between 2010 and 2019. Specifically, there was a slight decrease of just one percentage point in the diphtheria, tetanus, and pertussis vaccine. Overall, however, in 2023 it maintained a high vaccination coverage rate of 96.7%, although in 2019 it was 98%.

Between 2010 and 2019, Argentina also recorded a 12% drop in the first dose of the measles vaccine. And in Finland and Austria, declines of 8% and 6%, respectively, were reported for the third dose against diphtheria, tetanus, and whooping cough. “With vaccination, we see two things: on the one hand, in poorer areas, failures in fragile health systems that are unable to deliver vaccines to the entire population; and on the other hand, in rich countries, skepticism and denialism about vaccines and discrediting vaccination,” Bassat summarizes. Both realities are worrying, he admits, but emphasizes that deaths in the West from preventable diseases are “anecdotal” and places “the main problem” in the most vulnerable countries.

The leap from decades of progress to stagnation in coverage is due, according to scientists, to a combination of variables. The COVID pandemic, for example, accentuated the slowdown by triggering a cascade of setbacks whose effects have yet to be fully reversed. The authors estimate that the number of unvaccinated children reached 18.6 million in 2021, and although the 2023 counts reduced the figure to 15.7 million, this still represents a million more children than in 2019.

The authors also do not overlook the consequences of controversial political decisions , such as US President Donald Trump's decision to cancel programs supported by his aid agency (USAID) or withdraw funding from entities such as Gavi (the international vaccine alliance) or the WHO. In the article, they warn that, with all these decisions , "the historical and future progress of vaccination programs is at risk."

Vaccine hesitancy

Another key element they highlight to explain the slowdown in vaccination coverage is the increase in misinformation and vaccine hesitancy . These phenomena, they say, were already a "challenge" before the pandemic, but the COVID-19 health crisis exacerbated their impact. "The pandemic, which in many areas led to a decrease in trust in public health institutions and polarized opinions about the need for and safety of COVID-19 vaccination, has had diverse effects on public perceptions of the importance of routine childhood vaccination and the willingness to vaccinate," the authors admit.

A 2023 analysis reported that the prevalence of vaccine hesitancy ranged from 13.3% in the WHO Americas region to nearly 28% in the Eastern Mediterranean. In the US, they report, although parental support for this strategy remains overwhelming, concerns about safety and side effects increased, and preschool vaccine exemption rates in the 2023-2024 school year were the highest ever recorded. “While overall confidence in routine childhood immunization remains relatively high, the pandemic clearly exposed a strain of public distrust regarding health policies that will likely influence public perceptions of childhood vaccines in the future,” the scientists conclude.

Boi Ruiz remembers the death of the Olot child from diphtheria as the worst moment of his time leading the Ministry of Health. Because of the helplessness with which they endured those 25 days the child was hospitalized in the intensive care unit of Vall d'Hebron Hospital in Barcelona and the final outcome; and because of the measures they had to take. "We quarantined vaccinated children because, although they wouldn't contract the disease, they could be carriers. It was dramatic," he recalls. They had to protect a small group of families who, despite what they were witnessing, continued to refuse to vaccinate their children. And paradoxically, to achieve this, they had to isolate those who had done their homework.

“When there is no disease, vaccination is discouraged. But we should better communicate that the absence of disease is due to the vaccine,” reflects Ruiz. Bassat echoes this sentiment: “It's important to be a powerhouse and remember the importance of not resting on our laurels: vaccines are the best public health tool we have, but parents here are losing their fear of diphtheria, polio, or measles because they don't see it. What will change the anti-vaccine narrative in the US will be when they have their first case of polio and a repeat of what was seen in the 1950s, because it will be a disaster for their public image.”