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Statistically some vaccinated people will get measles. It doesn’t mean that the vaccine isn’t effective. Getty Images

Although the measles was eliminated from the United States nearly two decades ago, the virus has made quite the comeback this year.

So far, 626 people in the United States have come down with the measles, some of whom are adults claiming they previously received the measles-mumps-rubella (MMR) vaccine.

A rabbi in Detroit recently posted a video to YouTube saying he came down with the measles despite the fact he was fully vaccinated.

Earlier this month, a man who thought he was immune traveled from New York to Michigan and unknowingly infected 39 people.

And just last week, an Israeli flight attendant fell into a coma after contracting the virus. She had also received the vaccine, according to health authorities.

The startling occurrence of measles in vaccinated individuals has many people wondering if they’re fully protected against the virus.

Here’s the thing: although the measles-mumps-rubella (MMR) vaccine is extremely effective, it’s not 100 percent preventative.

As a result, a handful of people who get both doses of the MMR vaccine may still get sick after being exposed to the virus.

But this doesn’t mean the vaccine isn’t effective. In fact, it shows the opposite.

It’s crucial to get vaccinated anyway as it’s our best bet at containing the outbreaks, health experts say.

“The control of measles in many parts of the world is due to the vaccine, and though it is not 100 percent effective it is a crucial tool in controlling the spread of infection,” Dr. Amesh Adalja, an infectious disease specialist and senior scholar at the Johns Hopkins Center for Health Security, told Healthline.

One dose of the MMR vaccine provides 93 percent protection against the virus, while two doses provide 97 percent protection.

This means that if 1,000 people who received both doses are exposed to the virus, about 30 of them will catch the disease.

If another 50 unvaccinated people are exposed, approximately 45 of them will contract the disease, bringing the total outbreak count to about 75. So while 90 percent of the unvaccinated population contracted the disease just 3 percent of the vaccinated population are infected.

While these odds may seem daunting, without the vaccine, millions of people would contract the measles every year and there would be many more hospitalizations and deaths.

“Measles is not a mild illness — it is a serious condition that can cause complications such as pneumonia and encephalitis [brain swelling], resulting in the potential for long-term disability and even death,” Dr. Edward Chapnick, the director of infectious diseases at Maimonides Medical Center in Brooklyn, NY, told Healthline.

Despite the fact that the measles is so contagious, the virus can be prevented and controlled via vaccination, he added.

For one, even if you do contract the measles after being vaccinated, your symptoms will be milder and they will clear up much quicker.

Secondly, fully vaccinated people are much less likely to spread the disease to others, according to the Centers for Disease Control and Prevention (CDC).

“We owe it to ourselves and our loved ones to become protected so that those who are unable to receive the vaccine do not become infected,” Chapnick said.

Scientists aren’t entirely sure why certain individuals who are fully vaccinated will get the measles.

One theory is that some people’s immune systems may not respond to the vaccines, according to the CDC.

Where most people’s immune systems build a defensive shield to recognize and fight the disease after vaccination, some people’s immune systems may not develop enough antibodies to attack the virus.

“Unfortunately, individuals respond differently due to many factors including biological and environmental differences and variations. As a result, their immune system may not be as effective in responding to a pathogen compared to others and may not generate antibodies for rapid immune response as efficiently,” says Adriano de Bernardi Schneider, PhD, a postdoctoral scholar with the AntiViral Research Center at University of California San Diego.

Furthermore, those who have a weakened or immune system — such as cancer patients or people who have received a bone marrow transplant — may have a higher risk of catching the disease even if they were previously vaccinated.

The vaccine takes a couple of weeks to kick in, so if you recently got the shot, the vaccine may need more time to take effect.

Lastly, if the vaccine was handled improperly it could be defective.

“The MMR (and MMRV) vaccine must be stored appropriately and protected, for example, from light or freezing so if storage considerations aren’t ideal, a vaccine may lose its potency,” Adalja explained.

However, this isn’t really a threat anymore as healthcare providers are more educated about how to properly store and administer vaccines.

Although the measles vaccine was developed in 1963, it wasn’t until 1989 that public health officials started recommending the two-dose vaccine.

As a result, a handful of U.S. adults may have received an ineffective version of the measles vaccine or just one dose of the current MMR vaccine, which makes them slightly more susceptible to the virus.

“Since about 1989, two doses of measles vaccine have been the standard but there may be individuals who only received one dose during childhood or failed to obtain a second dose,” Adalja said.

If you received the two-dose version, you should be protected for life.

However, if you only received one dose, you may want to consider getting the second — especially if you are planning to travel abroad, advises Adalja.

Most people born before 1957 are immune to the measles as the infection was so widespread in that era that they were likely already exposed, according to Adalja.

If you were born after 1957, the CDC recommends checking your vaccination records, which contain a history of all the vaccines you received as a child and as an adult.

If you are unable to locate your records, you can get a blood test that can determine your level of protection by measuring the amount of antibodies in your immune system.

“If a person has a blood test showing they didn’t develop immunity as measured by antibody levels, they should be revaccinated,” Adalja said.

When in doubt, talk to your healthcare provider. They can help determine if you’re fully protected or could benefit from another dose of the MMR vaccine.

If you think you already got the vaccine but aren’t entirely sure, there’s no harm in getting it again.

At the rate of the current outbreaks, it’s better to be overprotected than put yourself and others at risk for infection.

Although the measles-mumps-rubella (MMR) vaccine is extremely effective, it’s not 100 percent preventative. Some people who’ve been fully vaccinated may still get sick after being exposed to the virus. Regardless, it’s important to get vaccinated anyway to help contain the outbreaks, health experts say.