Measles is the most contagious disease known. This can ravage a population without immunity like wildfire. Just look at what’s happening in Pennsylvania, says Patsy Stinchfield, executive director of the Measles Collaborative, a public health effort led by the National Infectious Diseases Foundation.
“In January, in Pennsylvania, there were 12 cases. Today we’re seeing over 100 cases a week and over 1,000 cases in Pennsylvania,” she said. “If Pennsylvania can see the disease spread this quickly, it can happen in any state with low vaccination rates.”
As vaccination rates have fallen across the country, many communities have become vulnerable. Nationwide, more than 4,000 cases of measles have been reported this year alone, the highest number in 35 years. Pennsylvania reported five deaths. New York State has declared a measles emergency.
Stinchfield says the recent wave of measles has many people wondering if they are at risk.
“It’s a very common question that people ask: ‘Am I immune? Am I okay? What should I do?’ And that’s exactly the right question that everyone should be asking themselves right now,” says Stinchfield.
The best defense is vaccination. Two doses of the measles, mumps and rubella vaccine are 97% effective, meaning 97% of people will have an immune response.
“The measles vaccine is safe. It is very effective and provides lifelong immunity,” says Dr. Adam Ratner, a pediatric infectious disease specialist in New York and author of Booster shotsa story of measles.
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But what happens if you don’t know your vaccination history or have only received one dose of measles vaccine? Should you get another dose? Infectious disease experts say it depends on several factors.
If you were born before 1957
People born before 1957 are presumed immune because at the time, measles was so common that almost everyone contracted it as a child, says Dr. Larry Kociolek, a pediatric infectious disease specialist at Ann & Robert H. Lurie Children’s Hospital in Chicago and an associate professor of pediatrics at Northwestern University Feinberg School of Medicine.
“It was thought that virtually everyone in the United States was infected with measles as a sort of childhood rite of passage,” Kocielek says. He says anyone who has ever had measles can be sure they are protected.
Of course, if you survived. Before vaccines, measles killed between 400 and 500 people each year in the United States.
If you were vaccinated before 1968
People born after 1957 and vaccinated before 1968 may need an extra dose. This is because a small group of people vaccinated at that time received an early and less effective version of the vaccine, using an inactivated or killed virus.
If you are unsure which vaccine you received, the Centers for Disease Control and Prevention recommends that you talk to your doctor about receiving one or two doses of the MMR vaccine.
If you have only received one dose of the MMR vaccine
Initially, American children received only one dose of the MMR vaccine. But that changed in 1989, after public health officials determined that a single dose was not enough to prevent outbreaks. That year, the official recommendation changed to two doses of the MMR vaccine for children, which remains in effect today.
Children need higher protection “because they tend to be at higher risk of exposure, since they’re often in groups like schools and daycares,” Kociolek says.
If you are in a higher risk group
One dose of the MMR vaccine is 93% effective, and traditionally, Kociolek says, that was considered sufficient protection for most adults unless they were at higher risk of being exposed to measles. Healthcare workers, people working in academia, and those traveling internationally are all part of this group. If you live or are in close contact with someone who is immunocompromised, you also need two doses of vaccine to protect them.
But given the recent, dramatic increase in measles across the country these days, “if you live in areas with high measles activity, it makes perfect sense for adults to get that second dose,” Kociolek says.
Ratner says it’s definitely worth asking your doctor if you should get a second dose.
Although measles is often thought of as a childhood illness, a large proportion of those sickened this year are unvaccinated adults – and people over 20 who lack immunity are at higher risk of serious complications.
Regardless of your age, “measles is a serious illness,” says Stinchfield.
She notes that receiving two doses of the vaccine may also help people at higher risk who cannot receive the MMR vaccine, including pregnant people, severely immunocompromised people and infants younger than 6 months.
If you really don’t know your vaccination history
If you’re just not sure if you’re protected against measles and can’t find vaccination records, you can get a test to check your blood antibody levels. But these tests aren’t perfect, says Dr. William Moss, a professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health.
“It’s possible that someone is actually protected and tests negative on one of these things,” Moss says.
Depending on your situation, your insurance may not cover the blood test. But most private insurance plans and Medicaid must cover another MMR vaccine for free.
Moss says that if you can’t confirm how many doses of MMR vaccine you’ve received, “I would say it’s easier and less expensive to just get another MMR vaccine, and there’s no harm in getting a second MMR vaccine or even an additional third dose of MMR.”
After all, it’s much better to be protected than infected.
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