Essential Facts Regarding Measles and the Combined Measles, Mumps, and Rubella (MMR) Vaccine
Hear Me Out:
Just a quarter century ago, measles was stamped out from American soil. Occasionally, cases popped up due to travelers from other countries like Europe, Africa, or Asia. But it wasn't until recently that we had a death from measles in the U.S.; and it wasn't until now that an anti-vaxxer took over as the head of our Department of Health and Human Services.
That department head, Robert F. Kennedy Jr., has sort of admitted that vaccines play a role in preventing measles. An opinion piece that appeared under his name at Fox News tried to dance around the vaccine message, stating that parents "should consult with their healthcare providers to understand their options" about the vaccine, and that "Good nutrition is the best defense against most chronic and infectious illnesses." Kennedy previously led an anti-vaccine organization that spewed misinformation so bad that it got kicked off of Facebook.
In contrast, the World Health Organization is able to put it bluntly: "Being vaccinated is the best way to dodge measles or spreading it to others." The CDC's website still has honest information about measles, including another straight-up statement that RFK, Jr. couldn't bring himself to say: "The best protection against measles is the measles, mumps, and rubella (MMR) vaccine."
While public health officials in Texas and other places are doing their utmost to control the latest outbreaks, RFK Jr. is busy on Fox News talking up the "perks" of measles infection and making the vaccine sound as bad as the disease. With the people in charge of the measles response sending mixed messages, I want to make sure the right information is getting out there. So here's the skinny on measles and the measles vaccine.
The MMR or MMRV shots are your best bet against measles
This is the first and most crucial fact: The measles vaccine shields you from measles. It is the best protection we have against measles, as both the CDC and WHO will readily confess. The World Health Organization estimates that measles vaccination saved 60 million lives worldwide between 2000-2023. Most measles deaths were among unvaccinated children under 5 or those who missed their recommended doses.
There are two types of measles vaccine available: the MMR vaccine that provides protection against measles, mumps, and rubella; and the MMRV vaccine that covers those three plus varicella, better known as chicken pox.
The recommended schedule for MMR or MMRV vaccination is to get the first dose at an age of 12 to 15 months, and the second dose at age 4 to 6 years. Infants who are traveling or live in a place with a measles outbreak can get a dose at age 6 months, although this protection isn't expected to last long, so they will still need the two more doses on the usual schedule. Adults and older children can also catch up with the vaccine if they missed it as kids or don't remember whether they got it.
Measles is one of the most contagious diseases under the sun, and can be fatal
Is it worth vaccinating against measles? Absolutely. Antivaxxers love to point out that measles was once a common childhood illness. But that doesn't mean it's harmless. Prior to vaccination, a typical year in the U.S. would see 500,000 measles cases. Those resulted in 500 deaths, 48,000 hospitalizations, and 1,000 cases of permanent brain damage from encephalitis.
Measles is also incredibly contagious, possibly the most contagious human disease there is. For comparison, the average person with the flu will give it to 1.3 other people. For ebola, that number is 1.8. For smallpox, before we eradicated it through vaccination, it was 3.5 to 6. Chickenpox is near the top of the list, with each sick person giving it to 10 to 12 others. But measles beats even that, spreading to 12 to 18 people, on average. I'm getting my numbers from this chart on Wikipedia. The exact number for each outbreak can depend on the specifics of the time and place, but these statistics are widely accepted.
Measles is so contagious that, after an infected person leaves a room, the air and surfaces in that room can infect people for the next two hours. This is why avoiding sick people isn't enough, and why authorities announce where and when a person with measles was in public, like two Philadelphia children's hospitals on March 7 and 10. Anyone who visited those places at those times is being told to check if they are protected from measles and to talk to their healthcare provider about getting the vaccine if necessary.
The measles illness is a heck of a lot worse than the vaccine
Kennedy made a common and incorrect antivaxxer argument when he said that the measles vaccine "causes all the same sicknesses" as measles. No, the vaccine does not give you measles. Even if he meant "all the same symptoms," it's still not true.
He particularly called out encephalitis, an inflammation of the brain that can result in death or brain damage. The measles vaccine causes 1-2 cases of encephalitis per one million children vaccinated. Measles, however, causes encephalitis in 1-3 out of every thousand children who get the disease, according to Encephalitis International. In other words, measles the disease has 1,000 times greater encephalitis risk compared to the vaccine.
Kennedy also claimed that the measles vaccine "causes deaths every year," which isn't true. The Infectious Disease Society of America states that "There have been no deaths shown to be related to the MMR vaccine in healthy people." There have been a very few deaths from vaccine side effects in children who were immunocompromised, which is why the first step in getting a vaccine is talking to a healthcare professional who can determine whether it's safe for you to receive the vaccine.
The vaccine can be given after you've been exposed to the measles virus
The optimal time to get an MMR vaccine is when you're young, at 12-15 months and 4-6 years old. The second-best time, if you've just been exposed to measles, is now. A dose of the vaccine can be given within 72 hours of being exposed to the virus to provide last-minute protection.
If you think you need the vaccine for this reason, ask your doc. There is another option, which is to get a dose of immunoglobulin instead. However, it has to be one or the other, not both; the globulin can cancel out the vaccine.
Vaccine immunity can fade, but not as much as RFK Jr thinks
After one dose of the MMR vaccine, you have a 93% chance of being protected against measles. After both recommended doses, that increases to 97%. This is exactly why two doses are recommended.
It's probably true that immunity from a measles infection lasts longer than from the vaccine, but the vaccine still provides lifelong protection to the majority of those who got their two doses. Kennedy said that vaccinated people lose "4.5%" of their immunity each year. I don't know where he got that number, but there's a study that postulated a 0.04% waning per year – that's around 100 times less than the number he cited.
For the love of god, you do not want "natural" immunity
In the 1950s and earlier, natural immunity – from getting infected – was the only measles immunity we had. Everybody still got the disease because unvaccinated children were being born constantly. Eventually, they'd encounter the virus, and get sick. As I discussed above, this was generally fine for most kids but catastrophic for some. If you haven't already, read Roald Dahl's letter about losing his daughter to measles. She was healthy, and then she had a routine case of measles, and then she felt "all sleepy" one day, and shortly afterward, she was dead.
The only way you get natural immunity is by rolling the dice. One child in every 1,000 died of measles. The other 999 carry that immunity with them for life, but only because they were lucky. The point of a vaccine is to give you the immunity without the risk of complications and death.
Which means, sorry, no measles parties. Or, as the Texas health department put it, "No! DSHS strongly advises against intentionally exposing anyone to infectious diseases like measles." As they correctly pointed out, you'd be risking severe complications and death for the attendees of the party, you can't predict how severe the symptoms will be, and you're creating a bunch of walking measles vectors who can transmit the virus to the elderly, unvaccinated, and immunocompromised. Vaccination, on the other hand, provides protection for 97% of those who receive the vaccine, with far smaller risks of complications.
How to know if you need a measles vaccine
When I said that "everybody" used to get measles as a child, that's true enough that the CDC and other health authorities rely on that fact to know who is immune. If you were born before 1957 (meaning you are 69 or older in 2025), you are assumed to have already survived a bout of measles.
You can also assume you are immune if you have medical records saying that you got two doses of the measles vaccine, or that you had a laboratory-confirmed case of measles, or that you have had a blood test that confirms your immunity.
If you don't remember whether you had the vaccine, you can get your immunity tested, but that's not necessary. As the CDC states: "There's no harm in getting another dose if you may already be immune to measles, mumps, or rubella."
If you live in Texas, where the largest measles outbreak is currently happening, this page from Texas Health and Human Services has information on staying safe, including where to get an MMR vaccine in Texas.
- Despite Robert F. Kennedy Jr.'s claims, the MMR or MMRV shots are the best protection against measles, a disease that can be fatal and is highly contagious, causing 1,000 times greater encephalitis risk compared to the vaccine.
- The World Health Organization estimates that measles vaccination saved 60 million lives worldwide between 2000-2023, with most measles deaths among unvaccinated children under 5 or those who missed their recommended doses.
- Vaccination is crucial, especially since immunity from a measles infection may not last as long as the vaccine immunity, and getting "natural" immunity by intentionally exposing oneself to measles is not recommended, as it carries a risk of severe complications and death.
