Eradicated diseases that could reappear in the US

In the United States, childhood vaccination rates have declined in recent years, affecting herd immunity levels. According to experts, if this trend continues or worsens, diseases such as measles, and even others that had already been eradicated, such as rubella or polio, could reappear.

This is the prediction of a study conducted by researchers at Stanford University School of Medicine in California, along with Baylor College of Medicine, Rice University, and Texas A&M University, and published last Thursday in the Journal of the American Medical Association (JAMA).

Research warns that the recent measles outbreak in West Texas, which infected more than 620 people, hospitalized 64, and killed two children, is a preview of what could happen.

The study, which used large-scale epidemiological models to simulate the spread of infectious diseases in the United States with different levels of childhood vaccination, predicts that, even with current vaccination rates, measles could again become endemic and circulate in the United States within two decades. And if vaccination continues to decline, it could happen sooner.

However, small increases in vaccination coverage would prevent this: for measles alone, increasing vaccination by 5% would reduce the number of cases enough to be within safe distance of returning to endemic levels.

Lead authors Mathew Kiang, assistant professor of epidemiology and population health, and Nathan Lo, assistant professor of infectious diseases, hope the study will provide useful data for decision-makers who set vaccination policy.

Why did vaccination rates decline?

In an interview with Kiang and Lo published in JAMA, the authors explain that The decline in vaccinations began during the pandemic of COVID-19 and that, since then, there has been a "general fatigue with vaccines" and "distrust and misinformation about their efficacy and safety," says Nathan Lo.

To understand the impact of this trend, the authors studied diseases that have been eliminated in the United States thanks to vaccines, such as measles, polio, rubella, and diphtheria, which They can have terrible complications, such as paralysis, birth defects or death.

The study used a large-scale epidemiological model of the entire U.S. population to simulate how infections would spread under different vaccination conditions and found that, at current rates, using average vaccination levels between 2004 and 2023, measles is already "on the brink of disaster," Kiang said.

"If vaccination rates remain the same, the model predicts that measles could become endemic in about 20 years , which would mean about 851,300 cases over 25 years, 170,200 hospitalizations, and 2,550 deaths. The other diseases are unlikely to become endemic under the status quo," he adds.

Nathan Lo explains that measles would become endemic because It is one of the most infectious diseases that exist, "So the number of people who need to be immune to prevent it from spreading is extremely high."

Furthermore, the MMR vaccine (measles, mumps, and rubella) has become particularly controversial due to spurious studies attacking its safety and linking it to autism. "Also, measles is more common worldwide, so travelers are more likely to bring it with them," says Lo.

Regarding children, Kiang warns that "if vaccination rates were to decrease by even 10% today, measles cases would skyrocket to 11.1 million over the next 25 years."

If vaccination rates were to fall by half, "we would expect 51.2 million cases of measles, 9.9 million cases of rubella, 4.3 million cases of polio, and 200 million cases of diphtheria over 25 years, resulting in 10.3 million hospitalizations and 159,200 deaths, as well as an estimated 51,200 children with neurological complications from measles, 10,700 cases of birth defects from rubella, and 5,400 people paralyzed by polio," Kiang estimates.

And in less than five years, "measles would become endemic, and rubella in less than 20. Under these conditions, polio became endemic in about half of the simulations in about 20 years," he predicts.

By state, the study found that Massachusetts, which has high vaccination rates, would be at low risk, while California and Texas were at higher risk because vaccination rates have declined significantly.

As for people who are most at risk, Nathan Lo points to those who are not vaccinated, babies between 6 and 12 months old, and immunosuppressed people (a sizable segment of the U.S. population).

Given this data, Lo and Kiang emphasize the importance of re-establishing trust in vaccines to combat "preventable" diseases.

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