Several diseases that were once nearly eliminated in wealthy nations are resurging as vaccination rates slip below critical thresholds. Measles, whooping cough, mumps, and polio have all shown alarming upticks in recent years, driven by a combination of vaccine hesitancy, pandemic disruptions, and access barriers. Here’s what’s actually happening with each one and why it matters.
Measles: The Fastest to Return
Measles is the canary in the coal mine for falling vaccination rates. It’s one of the most contagious viruses known to science, and it requires at least 95% of a community to be vaccinated to prevent outbreaks. When coverage dips even slightly below that line, cases appear almost immediately. A single infected person can spread the virus to a dozen others in any community that falls short of that threshold.
Global measles vaccination coverage sat at 84% for the first dose and just 76% for the second dose in 2024. That leaves enormous gaps. The consequences aren’t just a rash and a fever. Measles encephalitis, a dangerous swelling of the brain, strikes roughly 1 in every 1,000 cases. Other complications include pneumonia, blindness, and a rare but fatal condition that can appear years after the initial infection.
The financial toll is steep, too. A single measles outbreak in Clark County, Washington in 2019, involving just 72 cases, cost society approximately $3.4 million. That works out to nearly $47,500 per case. The overwhelming majority of those costs, about $2.3 million, went toward the public health response: contact tracing, testing, surveillance, and temporary staffing including nurses and interpreter services. Another $1 million came from lost productivity as patients and their families missed work and school.
Whooping Cough Surged in 2024
Pertussis, commonly known as whooping cough, made a dramatic return in the United States in 2024. Preliminary CDC data show more than six times as many cases were reported compared to 2023. Cases peaked around November 2024 and have since trended downward, but they remain elevated compared to pre-pandemic levels.
Whooping cough is especially dangerous for infants too young to be fully vaccinated. In older children and adults it can mean weeks of violent coughing fits, sometimes severe enough to crack ribs. In newborns, it can be fatal. The disease spreads through respiratory droplets, and immunity from both vaccination and prior infection fades over time, which is why booster shots matter for teenagers and adults, not just young children.
Mumps Keeps Breaking Through
Mumps outbreaks have followed a pattern of recurring waves globally, with peaks during 2004 to 2009 and again from 2016 to 2020. A systematic review spanning 21 countries documented over 71,000 cases across 47 studies. Europe accounted for nearly 45% of reported outbreaks, with the Netherlands and the United Kingdom seeing repeated clusters. The Americas made up about 25% of outbreaks, primarily in the United States and Canada.
Some of the largest recent outbreaks have been striking in scale. Moldova recorded nearly 14,700 cases in a single outbreak spanning late 2007 to early 2008. Bosnia saw close to 7,900 cases between 2010 and 2012. The Czech Republic reported over 9,600 cases across a five-year stretch. In the United States, one outbreak in 2016 to 2017 produced nearly 3,000 cases.
What makes mumps unusual is that outbreaks often occur in populations with moderate vaccination coverage. The attack rate in the Americas was 29.2%, compared to 7.6% in Europe, suggesting that even partially vaccinated communities can see significant spread in crowded settings like college dormitories and military barracks.
Polio Is Showing Up in Wastewater
Polio, a disease most people assume was conquered decades ago, is quietly reappearing. Between September and December 2024, a vaccine-derived form of poliovirus was detected in wastewater samples across five European countries: Spain, Poland, Germany, the United Kingdom, and Finland. The first detection came from Barcelona in September 2024. Within weeks, positive samples turned up at 16 additional testing sites in Warsaw, Munich, Berlin, Hamburg, London, Leeds, and other major metropolitan areas.
These detections don’t mean people are developing paralytic polio in large numbers. Wastewater surveillance picks up the virus circulating silently in communities, often through people who carry it without symptoms. But the presence of poliovirus in the sewage systems of wealthy, well-resourced nations is a warning sign. It means the virus is finding pockets of unvaccinated or under-vaccinated people where it can replicate and spread. If enough susceptible people cluster together, clinical cases of paralysis could follow.
Why Vaccination Rates Are Dropping
The decline isn’t driven by a single cause. The COVID-19 pandemic disrupted routine childhood vaccination worldwide, and many countries haven’t fully recovered. In 2024, roughly 14.3 million infants received zero doses of any vaccine, an increase of 1.4 million compared to 2019. While 131 countries have consistently reached at least 90% of children with a first vaccine dose since 2019, 47 countries have seen their coverage stall or decline, including 22 that previously met the 90% target and have since fallen below it.
Vaccine hesitancy plays a growing role, particularly in higher-income countries where parents may feel the diseases are too rare to worry about. Hesitancy around influenza and COVID-19 vaccines appears to be spilling over into attitudes about routine childhood shots. Financial barriers and access issues compound the problem. In the United States, increasing the number of healthcare providers who participate in programs offering no-cost vaccines to children would help close some of these gaps. Misinformation circulating on social media continues to erode trust in vaccines more broadly.
What You Can Do About It
If you’re unsure about your own vaccination status, it’s straightforward to catch up. Adults born in 1957 or later who lack evidence of immunity to measles, mumps, and rubella need one or two doses of the MMR vaccine depending on their risk factors. Healthcare workers face stricter requirements. Your doctor or pharmacist can review your records and identify any gaps.
For parents, the standard childhood immunization schedule covers all of the diseases discussed here. Staying on schedule is the single most effective way to protect your child and the broader community. These diseases didn’t disappear because of improved sanitation or nutrition. They disappeared because of vaccines, and they return when vaccination stops.