In October 2025, Dr. Justin Moll began doing something he'd never done in his career as a pediatrician: conducting triage in parking lots. At his Spartanburg, South Carolina clinic, he now checks children and their parents for measles symptoms outdoors about a dozen times daily. By February 2026, his practice had treated roughly 50 measles patients. Before last fall, he'd treated zero.

When Herd Immunity Collapses

Measles requires 95% vaccination coverage to prevent community spread. It's one of the most contagious diseases known—a single infected person can transmit it to 12-18 others in an unvaccinated population. The virus lingers in the air for up to two hours after an infected person leaves a room.

The United States crossed below that 95% threshold recently. MMR vaccination coverage among kindergartners dropped from 95.2% in 2019-2020 to 92.5% in 2024-2025. That seemingly small decline—less than three percentage points—translated into roughly 286,000 kindergartners now vulnerable to infection during the current school year.

The consequences arrived swiftly. The U.S. reported 2,280 confirmed measles cases in 2025, with three deaths—the first measles fatalities since 2015. By February 12, 2026, another 910 cases had been confirmed, putting the country on track for its worst year since the early 1990s. South Carolina alone surpassed 930 cases.

The Mechanics of Resurgence

Disease elimination is fragile. Measles was declared eliminated in the U.S. in 2000 after decades of sustained vaccination efforts. "Elimination" doesn't mean the virus disappeared—it means transmission no longer occurs continuously within the country. Cases still arrive from abroad, but they fizzle out before spreading widely when most people are immune.

That protection depends on maintaining high coverage everywhere. The problem isn't average vaccination rates—it's pockets of susceptibility. When unvaccinated people cluster geographically or socially, they create kindling for outbreaks. Of the 910 cases reported by mid-February 2026, 90% were outbreak-associated, meaning the virus found communities where it could spread efficiently.

The demographics tell the story clearly. Among 2026 cases, 94% were unvaccinated or had unknown vaccination status. Only 3% had received both recommended MMR doses. Children aged 5-19 accounted for 58% of cases, while those under five—too young for their second dose or, in some cases, any dose—made up another 25%.

The New Vaccine Resistance

What changed? The "medical freedom" movement gained momentum during COVID-19, fueled by pandemic backlash and social media misinformation. Skepticism about COVID vaccines metastasized into broader vaccine rejection. Exemptions from school vaccination requirements increased to 3.6% in 2024-2025, up from 3.3% the previous year. Seventeen states now report exemptions exceeding 5%.

The appointment of Robert F. Kennedy Jr. as U.S. Health Secretary amplified these trends. Kennedy has promoted unproven theories about vaccine dangers for years. His elevation to a position of authority sent a signal that vaccine hesitancy had official sanction.

Local leaders, meanwhile, grew reluctant to push back. Public health officials and school administrators who once enforced vaccination requirements now fear community uproar. The political cost of defending vaccines has risen sharply in many jurisdictions.

This isn't the first time vaccine confidence has wavered. In 2019, the U.S. saw 1,282 measles cases, mostly concentrated in Orthodox Jewish neighborhoods in New York where misinformation about MMR and autism had spread. That outbreak—934 cases in one community—nearly cost the country its elimination status. Minnesota's Somali-American community experienced a similar crisis in 2017 after anti-vaccine activists exploited concerns about autism, resulting in 75 cases.

But the current situation differs in scale and geography. The 2026 outbreaks span 24 jurisdictions across the country, from Maine to California, from North Dakota to Florida. This isn't isolated pockets anymore—it's a national pattern.

What Happens When Doctors Lose Ground

The medical burden extends beyond treating sick children. Dr. Moll's parking lot triage represents a new reality: doctors spending hours on containment rather than routine care. When measles enters a community, public health departments must trace contacts, verify vaccination status, and coordinate responses across schools and healthcare facilities. These containment efforts cost millions of dollars and strain already stretched resources.

The hospitalization rate in 2026—3% of cases—was lower than 2025's 11%, possibly because the virus spread among school-age children rather than infants and toddlers. But children under five still faced the highest risk, with 6% requiring hospitalization. Measles complications include pneumonia, encephalitis, and death. Even uncomplicated cases mean a week of high fever, rash, and misery.

The U.S. isn't alone. The UK lost its measles-free status in 2018 after 991 cases reestablished continuous transmission. Europe saw surges in 2018-2019. Samoa's 2019 epidemic proved devastating. The global pattern is consistent: when vaccination coverage drops, measles returns.

Rebuilding What Was Lost

Regaining elimination status after losing it takes years. It requires not just raising vaccination rates but maintaining them consistently while conducting surveillance to prove the virus isn't circulating. The UK still hasn't recovered its elimination status eight years after losing it.

The current outbreaks could become self-correcting in a grim way—as more children get infected, more acquire immunity through illness rather than vaccination. But that's the opposite of public health success. It means accepting preventable hospitalizations, permanent complications like hearing loss and brain damage, and occasional deaths.

The alternative requires confronting why vaccine confidence collapsed. Social media companies could do more to limit health misinformation. Political leaders could stop treating vaccine science as debatable. Schools could enforce existing requirements rather than expanding exemptions. Doctors like Moll could receive support rather than being left to improvise parking lot protocols.

Measles elimination was one of public health's genuine achievements. The virus that once infected nearly every child, killing hundreds annually in the U.S. alone, had been reduced to occasional imported cases. That achievement is unraveling not because the vaccine stopped working, but because fewer people are receiving it. The resurgence isn't a mystery—it's a choice, made incrementally through a thousand small decisions to skip shots, grant exemptions, and tolerate misinformation. Reversing it requires making different choices, starting now.