By Daniel Pastula, University of Colorado Anschutz Medical Campus

The measles outbreak that started in Texas in late January continues to grow. As of March 18, 2025, confirmed cases in the outbreak, which now spans Texas, New Mexico and Oklahoma, reached 321, surpassing the number of confirmed cases recorded for all of the U.S. in 2024. The vast majority of cases are in people who are not vaccinated. Meanwhile, a lack of clarity from health authorities is leaving people with questions about whether they need to get revaccinated.

In a Q&A with The Conversation U.S., Daniel Pastula, a neurologist and medical epidemiologist from the University of Colorado Anschutz Medical Campus and Colorado School of Public Health, explained how and when you should take action.

Should adults get another shot of the measles vaccine?

The measles vaccine, which first became available in the U.S. in 1963, contains a live but significantly weakened strain of the measles virus. This modified strain is too weak to cause measles, but it is similar enough to the wild type measles virus to train the immune system to recognize it. Most people who have received the live measles vaccine won’t need an additional shot now, but here is what you need to know:

People born before 1957 are presumed to have lifelong immunity because measles was so contagious that almost everyone contracted it before age 15. Unless there are special circumstances, they probably don’t need a vaccine now.

Most people born after 1957 would have received the shot as children, so they should be set for life. Physicians and public health experts don’t recommend most people in this group get a second measles shot, though there are exceptions.

In 1989, a limited outbreak of measles occurred among vaccinated school children. In response, the recommendations changed from one dose of the live measles vaccine to two doses for children. People fully vaccinated as children after that year do not need any additional doses.

Exceptions to these guidelines

There are two special circumstances where the previous recommendations may not hold.

First, if you were vaccinated between 1963 and 1967, one of the measles vaccines available at the time consisted of just proteins from the virus rather than a live, weakened version of it. Researchers soon realized this inactivated, or “killed,” vaccine was less effective and didn’t provide long-term immunity. Unless you know for certain you received the live vaccine, physicians and public health experts recommend that people vaccinated during those years get one dose of the live vaccine at some point.

Second, if you fall into a high-risk group – for example, if you are a health care provider, are traveling internationally or attending college, physicians and public health experts generally recommend getting a second dose if you have only had one.

For most adults without such risk factors, physicians and public health experts do not routinely recommend a second dose if you have previously received one dose of a live measles vaccine. If you have questions or concerns about your situation, make sure to ask your health care provider.

Except in very rare circumstances, there is no recommendation for a third dose of the measles vaccine.

Can you find out whether you’ve been vaccinated?

You might be able to! It’s worth checking. States actually keep vaccine records specifically for this reason, where you can look up your vaccine records or that of your kids. Your high school or college may still have your records, and so might your pediatrician’s office.

Should you get your antibody levels checked?

For most people, probably not.

A titer test checks the level of antibodies in your blood, and some people are asking their doctor to check their titers to determine whether they are still immune to measles. The problem is, the level of antibodies in your blood does not necessarily reflect your level of immunity. That’s because antibodies are just one part of your immune system’s infection-fighting force. Having a low level of antibodies does not necessarily mean your immunity has waned.

Other crucial elements of your immune response include B cells, T cells and other immune cells, but a titer test does not show their capabilities. For example, memory B cells might not currently be making antibodies against the virus but are primed to quickly do so the next time they see it. This is why antibody and titer tests should be used only in specific cases, in consultation with your doctor.

One example of when an antibody test may be warranted is if you are a health care provider born before 1957 and you want to make sure you don’t need another dose of the vaccine. You would use a test to see whether you have measles antibodies. But in this case you would be looking for a yes or no answer; the total amount of antibodies may not be very informative.

Is natural immunity better than vaccine-induced immunity?

Natural immunity – that is, the immunity you get after having measles – is effective. However, the downside is that natural infection with a wild virus is very risky. Before 1963, measles caused close to 50,000 hospitalizations and about 500 deaths each year in the United States, usually in children. It also caused over 1,000 cases of severe brain inflammation every year and carried several other long-term risks, such as permanent hearing loss or the wipe out of immunity to other diseases.

The point of vaccines is to create immunity without the risks of severe infection. It is basically a dress rehearsal for the real thing. The immunity from a vaccine is effectively the same immunity you get from having measles itself – but vastly safer than encountering the wild virus unprotected. One dose is 93% effective at preventing measles and two doses are 97% effective, and any breakthrough cases are likely to be much milder than a full-blown case of measles.

Can the vaccine cause measles?

No, the measles vaccine cannot cause measles because it contains a significantly weakened strain that has limited ability to infect and damage cells.

Some have claimed without evidence that the current outbreak in Texas was caused by the measles vaccine.

As part of the outbreak investigation, however, CDC and the Texas Department of State Health Services analyzed the genome of the virus causing the current outbreak and identified it as a wild measles virus. Researchers classify measles virus strains based on their genetic characteristics, or genotypes. They identified the outbreak virus as wild type genotype D8, and not the weakened measles vaccine strain, which is genotype A.

What are the risks of the vaccine?

That is a very reasonable question. Because the measles vaccine is a live, weakened virus strain, it can cause a mild, measles-like syndrome. For example, some people might have a slight fever, a rash, or some slight joint pain. These symptoms generally go away in a day or two, and most people don’t experience them. But the vaccine cannot cause measles itself, as it does not contain the wild measles virus.

In extremely rare cases, people can experience more significant reactions to the measles vaccine. It is important to remember that every single medical or health intervention carries risks – and that includes all medications and over-the-counter supplements. According to all available evidence, however, comparing the potential benefits against potential risks reveals that the risks of a signficant reaction to the vaccine are much lower than the risks of severe outcomes from measles itself.

Being vaccinated not only protects you and your family, but it also protects vulnerable people in the community, such as infants, cancer patients and pregnant women, who cannot be vaccinated themselves.

This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: Daniel Pastula, University of Colorado Anschutz Medical Campus

Read more:

• Texas records first US measles death in 10 years – a medical epidemiologist explains how to protect yourself and your community from this deadly, preventable disease
• Unverified reports of vaccine side effects in VAERS aren’t the smoking guns portrayed by right-wing media outlets – they can offer insight into vaccine hesitancy
• Vaccines and values: When you’re having a tough conversation about medicine, don’t just pile on evidence − listen to someone’s ‘moral foundations’

Daniel Pastula does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Feature Image: Should you get an additional shot of the measles vaccine? Hailshadow via Gett Images

The post Measles outbreak drives debate over revaccination for adults in US appeared first on The Cincinnati Herald .

By Daniel Pastula, University of Colorado Anschutz Medical Campus

On Feb. 26, 2025, Texas health officials announced the death of a child in a measles outbreak – the first measles death in the United States since 2015. The outbreak was first identified in early February in Gaines County, Texas, where just 82% of kindergartners are vaccinated against measles, compared with 93% on average across the country. As of Feb. 27, there were at least 124 confirmed cases in Texas and nearby towns in New Mexico.

In an interview with The Conversation U.S. associate health editor Alla Katsnelson, neurologist and medical epidemiologist Daniel Pastula explains why measles is so dangerous and how people and communities can protect themselves from the virus.

What is measles, and where does it come from?

Measles is an ancient disease caused by a virus that probably evolved in cattle and jumped into humans around 500 B.C. One of the first written accounts of it comes from a Persian physician named Rhazes in the ninth century C.E., and measles epidemics were described in medieval Europe and western Asia regularly beginning around 1100-1200. The virus got brought over to the Americas in the 1500s, and it wiped out large populations of native people as Europeans colonized the continent.

By the 1950s in the United States, there were 500,000 reported cases of measles each year – though the true number was probably closer to 4 million . It was so contagious, every kid was thought to have gotten measles by age 15. At that time, measles caused close to 50,000 hospitalizations annually and about 500 deaths, usually in children. It also caused over 1,000 cases of severe brain inflammation every year.

The first measles vaccine became available in 1963, and scientists improved it over the following decades, causing the number of cases to plummet. In 2000, measles was declared eliminated from the U.S.

Since then, there have been occasional minor flare-ups, usually brought in by international travelers, but by and large, measles outbreaks have been rare. No one had died of it in the United States in nearly a decade.

Today, measles infections in the U.S. are almost completely preventable with vaccination.

What are the typical symptoms of measles?

About 10 to 14 days after infection, people suffering from measles experience a very high fever, cold-like symptoms including a runny nose and sneezing, and eye inflammation called conjunctivitis.

Next, they may develop white spots called Koplik spots inside their mouth and a diffuse, spotty, red rash that starts at the head and neck, then descends across the entire body. This rash is where the disease gets its name – the word “measles” is thought to come from a medieval Dutch word for “little blemishes.”

Symptoms of measles infection take about three weeks to resolve. People are contagious from about four days before symptoms emerge to four days after the rash starts.

What are the possible severe outcomes of measles?

Epidemiologists estimate that 1 in 5 people who are infected with measles get sick enough to be hospitalized. About 1 in 10 develop ear infections, some of which may result in permanent deafness.

About 1 in 20 people develop severe measles pneumonia, which causes trouble breathing. Reports from west Texas this month suggest that many infected children there have measles pneumonia.

About 1 in 1,000 people develop severe brain swelling. Both measles pneumonia and brain swelling can be fatal. About 3 in 1,000 people die after contracting measles.

In about 1 in 10,000 who get sick with measles and recover from it, the virus lies dormant in the brain for about a decade. It then can reactivate, causing a severe, progressive dementia called subacute sclerosing panencephalitis, which is fatal within one to three years. There is no treatment or cure for the disease. I have seen a couple of suspected cases of subacute sclerosing panencephalitis, and none of these patients survived, despite our best efforts.

Given how contagious measles is and how severe the outcomes can be, physicians and public health experts are gravely concerned right now.

How does measles spread?

Measles is one of the most contagious infectious diseases on the planet. The virus is so infectious that if you are in a room with an infected person and you are not vaccinated and have never had measles before, you have a 90% chance of becoming infected.

The measles virus is transmitted by droplets released into the air by infected people when they cough, sneeze or simply breathe. Virus particles can survive suspended in the air or on indoor surfaces for up to two hours, so people can get infected by touching a surface carrying virus particles and then touching their face.

Who should get the measles vaccine, and how effective is it?

The vaccine for measles has historically been called the MMR vaccine because it has been bundled with vaccines for two other diseases – mumps and rubella. Most children in the U.S. receive it as a two-dose regimen, which is 97% effective against measles.

Children generally get the first dose of the vaccine at 12-15 months old and the second dose when they are 4-6 years old. Infants who haven’t reached their first birthday generally do not receive it since their immune system is not yet fully developed and they do not develop quite as robust of an immune response. In an emergency, though, babies as young as 6 to 9 months old can be vaccinated. If an infant’s mother previously received the MMR vaccine or had been infected herself as a child, her transferred antibodies probably offer some protection, but this wanes in the months after birth.

People born before 1957 are considered immune without getting the vaccine because measles was so widespread at that time that everyone was presumed to have been infected. However, certain people in this age group, such as some health care workers, may wish to discuss vaccination with their providers. And some people who had the original version of the vaccine in the 1960s may need to get revaccinated, as the original vaccine was not as effective as the later versions.

Based on available evidence, the vaccine is effective for life, so people who received two doses are most likely protected.

A single dose of the vaccine is 93% effective. Most people vaccinated before 1989 got just one dose. That year, an outbreak in vaccinated children with one dose spurred public health officials to begin recommending two doses.

People with certain risk factors who received only one dose, and everyone who has never received a dose, should talk to their health care providers about getting vaccinated. Because the vaccine is a live but weakened version of the virus, those who are severely immunocompromised or are currently pregnant cannot get it.

People who are immunocompromised, which includes those who have chronic conditions such as autoimmune disorders, are undergoing certain cancer treatments or have received an organ transplant, are more susceptible to measles even if they have been vaccinated.

In the current measles epidemic in Texas, the vast majority of people falling ill are unvaccinated. Public health officials there are urging unvaccinated people in affected areas to get vaccinated.

What measures can protect communities from measles outbreaks?

Vaccination is the best way to protect individuals and communities from measles. It’s also the most effective way to curb an ongoing outbreak.

High rates of vaccination are important because of a phenomenon called herd immunity. When people who are vaccinated do not get infected, it essentially stops the spread of the virus, thereby protecting those who are most susceptible to getting sick. When herd immunity wanes, the risk of infection rises for everyone – and especially for the most vulnerable, such as young children and people who are immunocompromised.

Because measles is so contagious, estimates suggest that 95% of the population must be vaccinated to achieve herd immunity. Once vaccine coverage falls below that percentage, outbreaks are possible.

Having robust public health systems also provides protection from outbreaks and limits their spread. Public health workers can detect cases before an outbreak occurs and take preventive steps. During a measles outbreak, they provide updates and information, administer vaccines, track cases and oversee quarantine for people who have been exposed and isolation for people who are contagious.

This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: Daniel Pastula, University of Colorado Anschutz Medical Campus

Read more:

• Measles is one of the deadliest and most contagious infectious diseases – and one of the most easily preventable
• CDC layoffs strike deeply at its ability to respond to the current flu, norovirus and measles outbreaks and other public health emergencies
• If my measles shot was years ago, am I still protected? 5 questions answered

Daniel Pastula does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Feature Image: Young children are especially vulnerable to measles. Bilanol via Getty Images

The post Texas reports first measles death in nearly a decade, sparking concern appeared first on The Cincinnati Herald .