Before vaccines, death and disability struck children. The injections then turned a once-common infection into something doctors only read about in textbooks.
But when immunization rates decline, past epidemics can return with full force, like measles outbreaks in American communities where parents chose not to vaccinate their children.
Imagine what would happen if you couldn’t even photograph the person you wanted to photograph.
Secretary of Health Robert F. Kennedy Jr., who founded an anti-vaccination group, is considering changes to several companies that make most of the vaccines for children in the United States that could cause them to stop selling them. Over the last year, he has transformed a government that has long championed the life-saving benefits of vaccines to one that has questioned their safety at home and abroad.
Shortly after Kennedy was nominated, questions swirled over how he would reform the U.S. vaccination system. Two Stanford University researchers wondered how many people would suffer if vaccination rates declined or if vaccinations for four of the most notorious diseases – polio, measles, rubella and diphtheria – were completely lost.
Epidemics often begin when Americans contract these illnesses overseas and return home. So epidemiologist Matthew Kiang and infectious disease physician Nathan Law built a model that simulates how four infectious diseases spread from sick travelers, based on each state’s vaccination rates.
With a significant portion of the population now vaccinated, some infections may not take hold quickly. However, over time, as more babies are born without vaccination, a larger proportion of the population will become susceptible.
The professors ran thousands of simulations for each disease and came up with a variety of possible outcomes. From there, they calculated the average number of deaths and disabilities over a 25-year period.
Their model shows that at current vaccination rates, the country is already on the brink of an explosion in measles cases, and that increasing vaccination by just 5% would effectively eliminate measles cases. But all four diseases could return if current infection rates were cut in half.
Researchers’ worst-case scenario modeling assumes that no one gets a shot for a quarter of a century. That doesn’t take into account the possibility that parents might go abroad to find a vaccine, or that politicians might intervene to get pharmaceutical companies to offer vaccines again.
But the results clearly demonstrate how important immunizations are and what is at stake when policy changes prevent Americans from vaccinating their children.
ProPublica shared key findings about that scenario with the Department of Health and Human Services. An agency spokesperson declined to discuss the modeling, but said that “HHS does not restrict access or insurance coverage to FDA-approved vaccines” and continues to routinely recommend vaccinations for children.
When they published their paper in early 2025, Kiang and Lo emphasized the success of the less extreme drop in vaccination rates, in part because reviewers suggested that was more realistic. At the time, Kennedy was in the early days of HHS.
But Kian said the scenario where no one will be able to get these vaccines a year from now is not that far-fetched. “Every week that goes by, it seems more plausible,” he said.
Roe said their goal is to show policymakers that “if we make certain decisions, this can happen.”
So ProPublica decided to show what a future without vaccines could look like.
if we lose
vaccine of
measles
Measles is one of the most contagious diseases in history. Children can spread the infection before the rash appears, and the virus can linger in the air for up to two hours after they leave the room.
Measles is a respiratory disease known for the patches that cover the body and can cause pneumonia and swelling of the brain. Before a vaccine was developed, measles affected nearly everyone and killed 400 to 500 Americans each year.
The model assumes that 3 out of every 1,000 people infected with measles will die.
if we lose
vaccine of
rubella
Rubella, also known as rubella, is usually mild in children and adults. However, it has devastating effects on the developing fetus. If an infection occurs very early in pregnancy, there is an up to 90% chance that the baby will be born with congenital rubella syndrome. These children often have heart defects, hearing loss, or blindness, and sometimes all three. There are also many people with intellectual disabilities. About one-third of infants with this syndrome die before their first birthday. During the rubella epidemic in the United States in the mid-1960s, 20,000 newborns suffered from congenital rubella syndrome.
if we lose
vaccine of
diphtheria
In the 1900s, diphtheria was known as the “strangling angel” because it killed so many children.
The disease’s name comes from the Greek word leather, because diphtheria toxin attacks the respiratory tract. Dead tissue builds up in the throat like a thick skin, blocking the swollen airway.
For those who escape suffocation, the toxin can cause nerve and heart damage. Patients who appear to be getting better may die after a few weeks.
Antivenom made from horse blood is urgently needed, but is in short supply. In other parts of the world, children have died waiting.
The disease is rare and much less contagious than measles or rubella. But it’s also far more deadly. The model assumes that only one infected traveler arrives every five years and that one in 10 unvaccinated people will die from diphtheria infection.
The researchers found that it was very likely that no one died from diphtheria during the 25 years covered by the model. But if we lose the vaccine, we will be playing a high-stakes game of roulette. The strangled angel could be devastating again.
The numbers of paralytic polio cases, measles deaths, congenital rubella syndrome cases, and diphtheria deaths in this article are averages generated from 2,000 simulations of each disease in a model created by Stanford University researchers Matthew Kiang and Nathan Lo. A “range” of possibilities means values within the upper and lower bounds of the 95% uncertainty interval. This means that for all simulations, 95% of the results fall within that range. In the worst-case scenario of death from diphtheria, the numbers used are at the upper end of this range.
For polio, the model generated an average of 23,066 paralytic polio cases, with a case range of 0 to 74,934 cases.
For measles, this model resulted in an average of 290,129 deaths, with a range of 285,271 to 294,286.
For rubella, the model generated an average of 41,441 cases of congenital rubella syndrome, with a range of 34,876 to 48,373.
For diphtheria, the model resulted in an average of 138,284 deaths, with a range of 0 to 1,460,394.
For current vaccination rates, researchers used each state’s average vaccination rate from 2004 to 2023.
The figure of six deaths from measles over the past 25 years comes from a report from the Centers for Disease Control and Prevention.
Last year, epidemiologists at Stanford University and other researchers published a peer-reviewed paper on this model in the Journal of the American Medical Association, showing what happens with less severe declines in vaccination.
