Even a 10% decline in vaccination rates would cause cases to skyrocket, leading to massive increase in demand for clinical laboratory MMR testing
As policymakers consider revisions to the current childhood vaccination schedule, a simulation model developed at Stanford University projects that declines in vaccination rates could lead to a dramatic resurgence of measles and other preventable infectious diseases over the next 25 years. Even at current vaccination rates, measles could once again become endemic in the US within two decades, the researchers reported.
The model suggests that clinical laboratories could one day find themselves testing millions of children for diseases once thought to be nearly eliminated in the US.
“With measles, we’re right on the cusp,” said senior author Nathan Lo, MD, PhD, assistant professor of infectious diseases, in a Stanford Medicine press release. “Increasing vaccination levels by just 5% brings the number of measles cases down, safely away from returning to endemic levels.”
“We’ve seen a worrisome pattern of decreasing routine childhood vaccinations,” said study senior author Nathan Lo, MD, PhD, in a Stanford Medicine press release. (Photo copyright: Stanford University.)
Millions of Measles Cases Predicted if Vaccinations Drop
To complete their study, the researchers looked at four infectious diseases:
“We used a large-scale epidemiological model to simulate all individuals living in the US and assigned them an age, vaccination status, immunity, state of residence, etc.,” Lo explained. “We then simulated how infections would spread under different vaccine conditions.”
Each state was modeled independently to account for variations in risk, noted lead author Mathew Kiang, ScD, assistant professor in the department of epidemiology and population health at Stanford. For example, Massachusetts is considered low risk due to high vaccination rates, whereas Texas and California are “higher risk because vaccination rates in both have dropped and there’s a lot of travel to those states,” he said.
The model assumed that infections would not cross state lines, “so the numbers could be an underestimate,” Kiang said.
He painted a grim picture of the scenarios projected by the model.
“If vaccination were to fall by even 10% today, measles cases would skyrocket to 11.1 million over the next 25 years,” he said. “If vaccination rates were cut in half, we’d expect 51.2 million cases of measles, 9.9 million cases of rubella, 4.3 million cases of polio, and 200 cases of diphtheria over 25 years. This would lead to 10.3 million hospitalizations and 159,200 deaths, plus an estimated 51,200 children with post-measles neurological complications, 10,700 cases of birth defects due to rubella, and 5,400 people paralyzed from polio.”
Lo suggested a more hopeful scenario in which “some fraction of the unvaccinated population seeks vaccination” as the diseases spread over the next decade. However, “if that were to happen, you can’t just flip a switch—once these diseases get unleashed, it would take time eliminate them again,” he said.
As of May 22, 2025, 1,046 cases of measles have been reported in the US this year, according to the Centers for Disease Control and Prevention. This year has been among the most active for measles since 2000. For the whole of 2024, 285 cases were reported.
More Contagious than COVID-19
All four diseases are far more contagious than COVID-19, Lo said, but measles “is in a different ballpark” as one of the most infectious diseases known to medicine. In a fully susceptible population, he said, one person can infect up to 20 individuals, but for the purposes of the simulation, they used a more conservative estimate of 12.
“There was a disruption to healthcare services during the pandemic, but declines preceded this period and have accelerated since then for many reasons,” he noted. “People look around and say, ‘We don’t see these diseases. Why should we vaccinate against them?’ There’s a general fatigue with vaccines. And there’s distrust and misinformation about vaccine effectiveness and safety.”
Another concern with measles is that the MMR vaccine “has become particularly controversial, partly due to a history of fraudulent medical research that raised safety concerns,” Lo said.
He added that compared to the other diseases, measles is more prevalent globally.
“Travelers importing a disease are like matches, and US under-vaccination is the tinder,” Kiang said. “With measles, you’re throwing a lot of matches in, and eventually something is going to happen.”
Clinical laboratory managers should prepare for an increase in demand for measles testing, especially for children
Clinical laboratory managers should be on the alert for new cases of measles. The US Centers for Disease Control and Prevention (CDC) has reported a surge in the highly infectious disease. Public health experts pointed to declining vaccination coverage as the primary cause. Officials in other countries have also reported outbreaks.
In 2000, the US declared that measles had been eliminated, meaning it “is no longer constantly present in this country,” the CDC stated on its website. However, the agency noted travelers can still bring the disease into the country and that there have been sporadic outbreaks since then.
In a new study, published April 11, 2024, in the CDC’s Morbidity and Mortality Weekly Report (MMWR), the agency reported that it was notified of 97 confirmed cases in the first quarter of 2024. That compares to an average of five cases during the first quarters of 2020 through 2023, the agency stated. In total, 338 cases were reported to the CDC between Jan. 1, 2020, and March 28, 2024, so the latest outbreaks amount to 29%—nearly a third—of the total.
“While the risk for measles for the majority of the US population still remains low, it’s crucial that we take the necessary steps now to prevent the continued spread of measles and maintain elimination in the US,” Adria D. Mathis, MSPH, lead author of the CDC report, told Healthline. Mathis is affiliated with the CDC’s Division of Viral Diseases at the National Center for Immunization and Respiratory Diseases (NCIRD).
“We have seen, in the region, not only a 30-fold increase in measles cases, but also nearly 21,000 hospitalizations and five measles-related deaths. This is concerning,” Hans Henri P. Kluge, MD (above), WHO Regional Director for Europe, told BBC News. “Vaccination is the only way to protect children from this potentially dangerous disease.” Clinical laboratories in the US that identify a case of measles from a positive test must report that result to public health labs. Thus, wise lab managers will track the rise in measles cases and prepare for increased demand for measles testing. (Photo copyright: World Health Organization.)
Renewed Threat to the US, Other Countries
The recent cases “represent a renewed threat to the US elimination status,” and “underscore the need for additional efforts to increase measles, mumps, and rubella (MMR) vaccination coverage, especially among close-knit and under-vaccinated communities,” Mathis told Healthline.
The MMWR report notes that most of the new cases were in persons under age 20, and that almost all were “in persons who were unvaccinated or whose vaccination status was unknown.” Most of the importations, the report states, were “among persons traveling to and from countries in the Eastern Mediterranean and African WHO [World Health Organization] regions; these regions experienced the highest reported measles incidence among all WHO regions during 2021–2022.”
In the US, vaccination coverage has been below 95% for three consecutive years. That is the “estimated population-level immunity necessary to prevent sustained measles transmission,” according to the federal agency. In 12 states and the District of Columbia, the coverage rate is below 90%. In total, “approximately 250,000 kindergarten children [are] susceptible to measles each year,” the CDC report states.
Measles vaccination coverage has declined globally, “from 86% in 2019 to 83% in 2022.” This left nearly 22 million children under the age of one susceptible to the disease, the report notes.
Earlier Measles Outbreaks in the US
The CDC performed its latest analysis following two larger measles outbreaks in 2019 among under-vaccinated populations in New York state.
The Associated Press (AP) reported that the 2019 epidemic, which totaled 1,274 cases nationwide, “was the worst in almost three decades and threatened the United States’ status as a country that has eliminated measles by stopping the continual spread of the measles virus.”
A vaccine for the disease first became available in 1963. Prior to its availability, “there were some three million to four million cases per year,” AP reported. Most people recover, but “in the decade before the vaccine was available, 48,000 people were hospitalized per year. … About 1,000 people developed dangerous brain inflammation from measles each year, and 400 to 500 died,” AP noted, citing CDC data.
US Not Alone in Fight against Measles
Other countries also are reporting spikes in measles cases. In a recently published rapid risk assessment, the Canadian government reported a total of 29 cases as of March 15, 2024, of which 21 were reported since Feb. 28.
“That’s already the largest annual total since 2019 and more than double the number of cases reported last year, as medical experts fear the number will rise while more Canadians travel in and out of the country this month for March break,” CBC News reported.
“New projections from a team at Simon Fraser University (SFU) in British Columbia show the grim possibilities,” CBC News reported. “The modelling suggests that vaccine coverage of less than 85% can lead to dozens of cases within small communities—or even hundreds if immunization rates are lower.”
Numbers are far worse in parts of Europe. In a February 2024 news release, the World Health Organization reported that in 2023, more than 58,000 people in its European region were infected by the disease, “resulting in thousands of hospitalizations and 10 measles-related deaths.”
According to WHO epidemiological data, countries in Central Asia, which is part of WHO’s European region, reported some of the highest numbers:
15,111 in Kazakhstan,
13,735 in Azerbaijan, and
7,044 in Kyrgyzstan.
The Russian Federation reported 12,723 cases and Turkey reported 4,559.
A WHO European Region Measles and Rubella Monthly Update notes that more than half of the regionwide cases—31,428—were reported in the last three months of 2023. More than 15,000 cases were reported in December. That compares to just 163 cases reported in 2021 and 942 in 2022. Nearly half of the cases were among children under the age of five.
Lack of Vaccinations among Children Blamed for Outbreaks
One factor that has led to the increase in measles cases was the disruption to immunization services caused by the COVID-19 pandemic. “This has resulted in a significant accumulation of susceptible children who have missed their routine vaccinations against measles and other vaccine-preventable diseases,” the WHO reported.
Among the region’s 53 member states, 33 had eliminated measles, WHO reported, but “this achievement remains fragile. To retain this status, a country must ensure that transmission of the virus following any importation is stopped within 12 months from the first reported case.”
In the UK, which reported 231 cases last year, the National Health Service has launched a campaign to improve vaccination rates, the BBC reported, noting that “more than 3.4 million children aged under 16 are unprotected and at risk of becoming ill.”
However, a public health campaign built on vaccination is successful only if a high rate of individuals get vaccinated. The Baby Boomer and Gen X generations had high rates of vaccination for smallpox, polio, etc. because the parents saw individuals in their family and neighborhood who became infected and suffered lifechanging consequences. They recognized that vaccination was a simple thing to provide protection from a potentially deadly infection.
Clinical laboratory managers and pathologists will want to follow the CDC’s ongoing reports of the number of cases of measles in this country. Today, the absolute number of new measles cases is relatively small. At the same time, in communities experiencing an outbreak of even a few measles cases, physicians may want to increase the volume of measles tests they order for their patients.
