Forgotten Diseases: How Declining Vaccination Could Bring Back Measles, Polio, and More

STANFORD, Calif. — America faces a brewing public health threat as vaccination rates continue to slide downward. Diseases once eliminated through widespread immunization could stage a comeback, with measles likely to lead the charge.

A new investigation published in JAMA reveals that measles could become endemic in the U.S. again within 21 years if current vaccination trends persist. The consequences would worsen dramatically if rates drop further, potentially affecting millions of Americans with diseases many have never seen firsthand.

Most parents today have never witnessed a child with measles, let alone polio or diphtheria — a fact that, according to co-author Dr. Nathan Lo, contributes to “a general fatigue with vaccines” and growing “distrust and misinformation about vaccine effectiveness and safety.”

The Hidden Cost of Vaccine Hesitancy

The research team used computer modeling to project what happens under various vaccination scenarios for four diseases: measles, rubella, polio, and diphtheria. Their findings paint a concerning picture.

Under current vaccination rates, which vary between 88% and 96% across states, measles would likely reestablish itself within two decades, causing approximately 851,000 cases over 25 years.

A 10% decline in vaccination rates would dramatically increase this number to 11.1 million cases. Should rates drop by 50%, the model predicts more than 51 million measles cases over 25 years – affecting roughly 15% of the entire U.S. population.

These aren’t just numbers on a page. They represent actual suffering: permanent brain damage, birth defects in babies whose mothers contract rubella during pregnancy, paralysis from polio, and tens of thousands of preventable deaths.

The study concluded that “measles [is] likely to be the first to return to endemic levels and may occur even under current vaccination levels without improved vaccine coverage,” with its spread driven by lower immunization rates in certain states.

The threat is already materializing. A recent outbreak in western Texas infected more than 620 people, leading to 64 hospitalizations and the deaths of two children.

Regional Differences Create Vulnerability Hotspots

The research uncovered significant regional variations in disease vulnerability. Texas faces particularly high risk for measles outbreaks due to its combination of lower vaccination rates, large population, and international travel connections.

“Massachusetts has high vaccination rates and was consistently low risk. Both California and Texas were higher risk, even after accounting for larger population size, because vaccination rates in both have dropped and there’s a lot of travel to those states,” Kiang noted in a statement.

This patchwork of protection creates weak points where outbreaks can begin and spread, even when overall national vaccination rates appear adequate.

The timing of these findings coincides with growing political debate about childhood vaccination requirements. Some proposals include removing certain vaccines from the recommended schedule or eliminating school vaccine mandates altogether – moves that would accelerate the decline in coverage.

A Path Forward

Despite the concerning projections, the research offers hope. Boosting measles vaccination by just 5% would prevent its return to endemic status and slash the 25-year case count to about 5,800 – a 99% reduction compared to what would happen with a 10% decline.

“With measles, we’re right on the cusp. Increasing vaccination levels by just 5% brings the number of measles cases down, safely away from returning to endemic levels,” Dr. Lo explained. “These are the kinds of small percentages that can really be a tipping point. It’s empowering that a small segment of the population can make a difference here.”

After generations protected by vaccination, Americans now have the luxury of focusing on extremely rare vaccine side effects rather than the diseases themselves. But that equation changes dramatically when diseases return.

“It’s worth emphasizing that there really shouldn’t be any cases at this point, because these diseases are preventable,” Kiang added. “Anything above zero is tragic. When you’re talking about potentially thousands or millions, that’s unfathomable.”

The message from researchers is clear: societies that forget their public health history risk repeating it. Vaccines don’t just protect individuals – they maintain a barrier that keeps dangerous diseases at bay. As that barrier weakens, the diseases remain poised to rush back in.