Before vaccines, nearly every child in the United States caught the virus. Today, however, public health experts emphasize that while natural immunity does occur after infection, the risks of measles are far too high when compared to the protection offered by the measles, mumps and rubella (MMR) vaccine.

Early 2025 data show rising cases in the U.S., a reminder that measles still spreads quickly wherever vaccination rates dip.

Natural immunity and the role of vaccines

“Natural immunity is wonderful. It's part of the evolution of the human body that has taken all our exposures and creates a memory for them, so that we can protect ourselves in the future. Vaccines augment (improve) that. There are some infections that an individual doesn't have to go through, or are so severe to go through, that receiving a vaccine is more valuable,” says Doug Kasper, MD, infectious disease specialist with OSF HealthCare.

He notes that measles is one of those infections.

“Measles is highly infective and has potential complications in our child population. The key with measles is that the vaccine is so effective at preventing infection. It's unanimously beneficial to receive and has been that way for a long time in the United States.”

For older generations who remember having measles as kids, it can be easy to assume it wasn’t serious. But modern evidence paints a different picture: measles can lead to pneumonia, hospitalization, brain inflammation, long-term complications and death – even in healthy children.

Why measles vaccination remains essential for kids

“Fortunately, measles vaccination remains part of the normal pediatric vaccine schedule. It's something that would be discussed with the parent regarding their child at a standard visit,” Dr. Kasper says. “We strongly recommend all children receive all their childhood vaccinations, which includes the measles, mumps and rubella (MMR) vaccine. The timing of that vaccine begins at one year of age, but it can sometimes be given earlier if there is a local outbreak of measles in the community.”

MMR vaccination rates need to remain extremely high, typically above 95%, to prevent outbreaks. However, declining vaccination rates across parts of the Americas have caused concern. The Pan American Health Organization recently warned that the region may lose its measles elimination status without urgent action.

Vaccines build a “library” of protection

The goal of vaccination isn’t to replace the body’s defenses – it’s to strengthen them.

“In the hospital, we tend to see people that get sicker, so that's what we focus our efforts on. But a lot of medicine is done outside of the hospital, and that is preventive medicine,” Dr. Kasper says. “So, the strategy with vaccine is to try not to get sick or try to get less sick than you would've. Use the utility of the vaccine, along with natural immunity, to build up your individual reservoir as much as possible to protect you in the future.”

This “reservoir” or “library” of immunity is especially important with a virus as contagious as measles, which can linger in the air for hours and infect up to 90% of unprotected people who are exposed.

Localized outbreaks are driving current cases

While measles is not widespread across the U.S., localized outbreaks continue to occur in communities where vaccination rates have dropped. Public health departments monitor these cases closely and respond with tools such as:

• Rapid case investigations
• Community education
• Mobile vaccination units
• Early MMR vaccination for children who qualify

Without high vaccination coverage, these small outbreaks can grow quickly. That’s why maintaining strong MMR rates is essential – to protect children, prevent community spread and preserve decades of progress toward measles elimination.

For more information on measles symptoms and long-term risks, visit the OSF Newsroom.

Video Interview Clips

El sarampión es una enfermedad viral altamente contagiosa que se transmite por el aire al toser, estornudar o incluso al hablar. Aunque muchos creen que es una enfermedad del pasado, en los últimos años han surgido nuevos brotes en distintas partes del mundo, incluyendo Estados Unidos. Se estima que una sola persona infectada puede llegar a contagiar entre 9 y 10 personas si no están vacunadas.

En este episodio, conversamos con Virginia Morgan, enfermera de medicina familiar de OSF Healthcare, quien nos explica qué es el sarampión, los síntomas más comunes y nos habla de la importancia de la vacuna.

El viernes 2 de mayo, el Chicago Department of Public Health confirmó dos casos de sarampión en el condado de Cook.

Aquí está el enlace en Spotify.
Aquí está el enlace en YouTube.

The respiratory viral infection, although thought eliminated in the U.S. in 2000, has reemerged, especially among unvaccinated individuals. As of early April 2025, the Centers for Disease Control and Prevention (CDC) has reported more than 600 confirmed cases of measles.

Measles is extremely contagious

"The key to measles is how highly infectious it is. Each person that has measles will infect between 12 and 18 people in an unvaccinated situation," says Doug Kasper, MD, an infectious disease specialist with OSF HealthCare. "The key for controlling measles is widespread vaccine use."

For reference, each influenza patient, on average, will infect one to two others.

The measles vaccine is normally offered once a child has reached one year of age. It's a two-shot series, which came on the market in 1963. Dr. Kasper says this gives medical experts decades of data that show a correlation between people receiving the vaccine, and close to zero circulation of the virus in the United States.

The states with measles outbreaks are in unvaccinated people, and no breakthrough cases (in those who have received the vaccine) have been reported, Dr. Kasper adds.

The long-term risks for unvaccinated measles patients 

"There is emerging information that vaccination not only protects an individual from not becoming ill or having less severity of illness with a viral exposure, whether that's measles, chicken pox, influenza or COVID-19, but that there are long-term risks from viral infections that we do not appreciate in the moment," Dr. Kasper says. "Some of these have been associated with memory loss or dementia as somebody ages. Some of these are associated with organ disease like hepatitis or kidney disease."

Subacute Sclerosing Panencephalitis (SSPE)

SSPE is a rare, deadly degenerative disease of the central nervous system that can happen seven to 10 years after a measles infection. Young children, pregnant women and immunocompromised people are the most at-risk for SSPE. One to three out of every 1,000 children who become infected with measles will die from respiratory and neurologic complications, the CDC says.

SSPE symptoms happen over four stages.

-          Stage 1: Personality changes, mood swings or depression. There may also be fever and headaches, this stage can last up to six months

-          Stage 2: Muscle spasms and uncontrolled movement problems. Loss of vision, dementia and seizures can occur

-          Stage 3: Twisting movements and rigidity. Sometimes death

-          Stage 4: Serious brain damage, including areas of the brain that control breathing, heart rate and blood pressure, leading to coma and death

Immune amnesia

Another long-term impact of measles is known as immune amnesia. The American Society for Microbiology (ASM) calls immune amnesia “one of the most unique and most dangerous features of measles pathogenesis.” The extremely rare condition causes people’s immune systems to “forget” how to fight off infections and makes the person more susceptible. The ASM determined it normally takes two to three years after a measles infection for protective immunity to return.

A measles outbreak was declared in Northeast Illinois in early 2024 and declared “over” by the Illinois Department of Public Health (IDPH) in June. The expectation of statewide health experts is that measles will return to Illinois in the coming months. This is mainly due to heavy travel through Chicago airports and summer festivals. County health departments have now been tasked with keeping an eye on their measles vaccine rates and identifying areas where vaccine rates are low. 

Peoria County's measles vaccine rate is quite high, around 95%. But outlying communities in central Illinois have lower vaccine rates, normally more rural counties. Health experts at Michigan Medicine call the Great Lake State “ripe for a measles outbreak,” as only 66% of toddlers receive the recommended childhood immunizations.

Measles symptoms 

"Measles typically presents with a high fever, typically much higher than what we'd see with seasonal colds or influenza. Fevers can be 104 or 105 degrees Fahrenheit," Dr. Kasper says. "That's followed by a runny nose and a characteristic rash. This typically develops on the head and then spreads down the rest of the body."

“We don’t want to go back”

"Measles at its peak, in the 1950s before the vaccine, led to a significant number of hospitalizations in young children. Around 50,000 hospitalizations were estimated per year and about 500 deaths," Dr. Kasper says. "We don't want to go back to that scenario in any capacity, where we have a large number of unvaccinated people. The outcomes could be too severe." 

Immunocompromised people like those who have received an organ transplant, cancer patients or those on long-term therapies that could impact their immune system, are at high risk for measles. 

Why vaccines are so important right now

Summer travel along with large crowds at places like airports and theme parks, will likely bring more measles cases to the United States. 

"This time, as good as any time, is to make sure somebody is updated on their vaccinations. If somebody isn't sure if they were vaccinated as a child, they should talk to their primary care provider about testing or receiving the vaccine. If someone is immunocompromised and they might be at a higher risk for measles through travel in areas that have exposure, they should talk to their primary care provider about the vaccine," Dr. Kasper says. "If someone has young children or is at an age where vaccine is recommended, we wholly recommend for them to discuss with their provider to remain up to date on their vaccine series."

Vaccine hesitancy continues to be a topic of discussion, one that Dr. Kasper recommends patients openly discuss with their medical provider. 

Natural immunity is not a viable option with measles. The highly infectious nature of the virus, along with the severity of symptoms and potential for long-term complications, make it an illness people need to try and avoid entirely. 

To choose a primary care provider, visit the OSF HealthCare website.

Video Interview Clips

The third week of March marked a regrettable milestone. The number of measles cases soared past the number in all of 2024. Dana DeShon, APRN for Peoria, Illinois-based OSF HealthCare, says globally the mortality rate of children worldwide has been reduce by 51% by just the act of vaccinating them. Vaccines save more than 4-5 million lives each year and have prevented approximately 50 million deaths between 2000-2019.

However, DeShon worries that in the United States, vaccine hesitancy will bring measles back as a public health crisis. The advanced practice registered nurse has been involved with the United Nations Foundation initiative called Shot@Life through which she and others lobby Congress to fund vaccine support for children in low-income countries.  According to Deshon, the funding accounts for less than 1% of the total U.S budget but saves 2.5 million lives every year worldwide.

However, these days, she’s focused on vaccinations at home.

DeShon says most of the population hasn’t seen the devastating impact of the highly contagious measles because it was eradicated in 2000. But measles is making a resurgence because of vaccine hesitancy. And measles is the most contagious of all vaccine-preventable diseases.

It begins with a runny nose, watery eyes and then a rash so people can be walking around, spreading the airborne virus before severe symptoms develop.

“You’re contagious four days before that rash and up to four days after so we could have 8 to 10 days of people walking around not even knowing they have measles and then they’re just spreading it around to people at risk. Obviously, the people most at risk, are the people who are not vaccinated,” DeShon points out.

That includes babies who can’t be vaccinated until age 1, along with pregnant women and immunocompromised cancer patients who can’t get vaccinated.

Vaccine hesitancy was fueled in the 1990s by a bad study from a physician who has since lost his license to practice medicine. The research, published in a respected medical journal, The Lancet, involved only 12 patients and falsely linked vaccines with autism. DeShon said the study has been retracted and there is, in fact, NO scientific evidence that vaccines cause autism.

She emphasizes the National Institutes of Health (NIH) spent millions on research.

“Outside research was also done and there were no links that they could find from that original Lancet study. It got to the point that they said, ‘We’re not going to do anymore studies because they did not see a link between autism and the MMR (measles, mumps and rubella) vaccine.”

Measles vaccination rates are falling

The Kaiser Family Foundation says measles vaccination rates in most U.S. states have fallen below the 95% threshold scientists consider necessary for so called ‘herd immunity’ to control the disease, and those rates have continued to drop. That’s concerning for DeShon.

“How are we going to stop this? It is not vitamin A. Vitamin A is not going to stop the measles outbreak. We need vaccinations. That is what is going to stop the outbreak that we are seeing, not just in west Texas, but all over in these pockets we’re seeing in the United States right now.”

DeShon stresses when the population is vaccinated, measles goes away. Receiving one and two doses of measles vaccine is 93% and 97% effective, respectively, in preventing measles.

She points to an outbreak at a Chicago migrant shelter last year. Fifty-seven measles cases were associated with people in the shelter. Most cases occurred in people who were unvaccinated. A prompt and coordinated response with a mass vaccination campaign reduced the size and duration of the outbreak and stopped what might have become a statewide public health concern.

The Centers for Disease Control and Prevention (CDC) says measles can lead to severe complications, including pneumonia, encephalitis (inflammation of the brain), and in some cases, death. Children, especially those younger than 5 years old, are at a higher risk of developing serious complications from measles.

A school-age child in Texas died from the measles and the New Mexico Department of Health is reporting the death of an unvaccinated adult who tested positive for measles. Even if a child survives measles, it can have long-lasting effects.

A condition called subacute sclerosing panencephalitis, or SSPE, a degenerative neurological condition can develop seven to 10 years after a measles infection, according to DeShon. 

The disease carries a heavy toll. So DeShon reminds everyone that while vaccination is a personal decision, it impacts health systems, communities, and the most vulnerable among us.

“When it comes to the point that this is something that is so contagious, and now deadly, then we really need to stop and think, ‘We need to be doing this, not because of me but because of those around me.’”

If you’re unsure whether you have immunity against measles, talk to your health care provider about your options.

OSF pediatric nurse practitioner Dana DeShon

There’s a misperception that measles is a thing of the past.

Not so.

Measles was declared eliminated in the United States in 2000 but is seeing a resurgence in 2024. As of March 22, there have been 64 cases across the U.S. – compared with 58 in all of 2023. The cases have appeared in at least 17 states so far, including Illinois and Michigan.

The cause of the increase is two-fold – the number of people who are unvaccinated has increased and the rise in international travel to destinations such as Britain, Austria and the Philippines, where outbreaks have occurred.

According to Alissa Bartel, a nurse practitioner with OSF HealthCare, there’s no reason to be concerned yet. “I think it's always good for parents to be aware, be educated and not alarmed, but know that it is possible, especially in those kids who are at highest risk,” she says.

Measles is a highly contagious disease caused by a virus. It spreads when an infected person breathes, coughs or sneezes. That person can spread measles to others even before knowing they have the disease — from four days before developing the measles rash through four days afterward.

Symptoms include a high fever, cough, runny nose and a rash that starts at the top of the head and travels down the trunk to the lower extremities. Complications can lead to pneumonia, swelling of the brain and even death.

Measles can affect anyone but is most common in children.

“The most vulnerable of developing measles would be those who are not vaccinated; so kids under 5 years old or any child who has not chosen to be vaccinated, also those who are receiving chemotherapy or any medications that might make them immunocompromised,” says Bartel. “Also, pregnant women are very high risk, not only for themselves if they haven't been vaccinated, but also for the child that they're carrying.”

The best way to prevent getting sick with the measles and spreading it to others is from the measles-mumps-rubella (MMR) vaccine.

“We’ve had so many vaccines that have helped us to drive so many serious illnesses and diseases away,” says Bartel. “However, we are seeing a lot of them emerge again. It’s important for us to educate our patients on vaccines, not only for ourselves, but to protect others who can't receive vaccines.”

The Centers for Disease Control and Prevention (CDC) recommend children get their first MMR dose between the ages of 12-15 months. The second dose is between ages 4-6. Teenagers and adults require only one dose and should get it as soon as possible.

According to the CDC, two doses of MMR vaccine are about 97% effective at preventing measles, and one dose is roughly 93% effective.

For parents experiencing vaccination hesitancy, Bartel recommends having a conversation with your family physician. Experts stress it’s important to eliminate potential barriers such as cost. Children can be vaccinated for free through private insurance or the Vaccines for Children Program, a federally funded, state administered program that provides free vaccines to eligible children ages 18 and younger. 

Some parents may not realize the potential seriousness of their young ones contracting measles. The World Health Organization reports that the measles vaccination prevented 56 million deaths between 2000 and 2021. An estimated 128,000 people died from measles in 2021 – mostly children under the age of 5.

“Open the conversation about vaccines and vaccine hesitancy and then also know that you can trust your provider. They know what's best for your children,” she says. “They can also point you to really good resources, trusted resources. If you like to read about things and make really educated decisions, we can empower our patients to do that.”

For more information on the measles, visit OSF HealthCare. 

Interview Clips 

She was about to become a statistic in a polio epidemic and battle a disease that still impacts her in 2024.

Though polio is nearly eradicated today thanks to childhood vaccinations, both the disease and the shots have garnered headlines lately. This month, Paul Alexander, who spent much of his life in an iron lung, passed away at age 78. And the state of Illinois is combating a measles outbreak, reminding us of the importance of vaccines.

Kemnetz’s story

Kemnetz says the week she got her headache that led to a polio diagnosis was a painful blur.

“All my senses were on high alert,” she says. “The littlest sound was like somebody stomping next to my ear. We had a little night light. I couldn’t even stand to have it on.”

On Sunday, the family doctor made a house call and immediately called for an ambulance. Kemnetz wound up at Mercy Hospital in Urbana, Illinois (now OSF HealthCare Heart of Mary Medical Center). That next month, she says, was also a blur. Among other things, doctors upon her arrival performed a spinal tap to examine Kemnetz’s spinal fluid. She also recalls waking up one day with doctors preparing to put her in an iron lung to help her breathe.

“I screamed at my parents not to put me in that. I was terrified,” Kemnetz says.

After leaving the hospital, Kemnetz got more treatment near her home before spending over a year at a hospital in New York. There, she reprogrammed her leg muscles to work through repetitious exercises. It’s what we know today as physical therapy. Eventually, she returned to a mostly normal life and a career in real estate.

Polio then vs. now

Albert England, MD, an infectious disease physician at OSF HealthCare, says polio has been around “for a long time.” There’s even evidence of ancient Egyptians having it, he says. The disease is caused by a virus that “invades the nervous system and can cause total paralysis in a matter of hours,” according to the World Health Organization (WHO). Other symptoms are flu-like, including fever, difficulty breathing, fatigue, headache, vomiting, a stiff neck and pain in the arms or legs.

Dr. England says today, doctors use ventilators to help sick people who can’t breathe. But back in 1952, the iron lung – which Kemnetz got acquainted with – was the help available for people with polio.

“It produced negative pressure around the patient, allowing the lungs to expand and contract regularly,” Dr. England explains.

“It was like having CPR 24/7,” Kemnetz says of lying in the tube. “So uncomfortable.”

Kemnetz also gave blood to help develop a polio vaccine, the number one way we have come to fight that disease and many others. It’s a topic she’s passionate about today.

“We have to save the children,” she says.

The United States Centers for Disease Control and Prevention (CDC) says children should get four doses of the polio vaccine as a part of routine childhood vaccinations. The CDC says while it’s rare, adults who know or suspect they did not get the shots as kids should get them as adults. Adults who are at an increased risk of getting the disease, such as working in a laboratory where the virus may be present, can get a booster shot.

“The vaccine prevents illness by developing antibodies,” Dr. England explains.

Kemnetz today

In 1985, Kemnetz developed post-polio syndrome, a disorder that weakens the nerves and muscles. She says her hands “look nice,” but everyday tasks like writing, eating or shuffling cards are tough.

“There are just not as many neurons providing the strength the people need,” Dr. England says of post-polio syndrome.

But, after being told in 1952 that walking, having children and living a long life was unlikely, Kemnetz is counting her blessings. Among them are the chances to recount her life story with her children and grandchildren.

“I think I thumbed my nose at them pretty good,” she quips about her prognosis back then. “The word ‘can’t’ isn’t in my vocabulary.”

Interview clips

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