This year there have been more reported cases of measles in the United States than in any year in recent memory. Wasn’t measles eliminated from the United States in 2000? If so, why are we seeing so many cases this year?
The reason is that measles is still quite common in other parts of the world. The measles outbreaks this year happened because non-immune persons contracted measles infection while traveling abroad, and then spread measles to others when they returned to the U.S. Measles is a virus that causes a fever illness associated with rash, and may infect other organs such as the lungs (pneumonia) and brain (encephalitis), sometimes leading to death.
Measles is very contagious. It infects up to 90 percent of non-immune people who come in contact with it. The measles virus can remain suspended in the air for two hours after an infected person leaves a room, continuing to infect people even without direct contact.
The only way to prevent the spread of measles is to make sure that almost all of us, at least 94 percent, are protected from it by immunity. Though 94 percent is a high bar, it is required to prevent measles outbreaks.
In 2000, a measles outbreak would have been improbable due to immunity rates. Enough people were immune then in the U.S. such that imported measles cases would not spread. But since 2000, vaccination rates have eroded, and this set the stage for what we are seeing this year.
Survivors of measles enjoy lifelong immunity. For those who have never had measles, the only reliable way to become immune is to receive at least one, and preferably two, doses of the MMR vaccine. The MMR vaccine provides immunity against measles as well as mumps and rubella. MMR is usually given to infants at age 12-15 months, and again at age 4-6 years. The MMR vaccine has been used since 1971.
Most persons born before 1957 are considered immune, since measles was so common in the U.S. at that time. Those born in 1957 or after may or may not be immune.
How do you know if you are immune to measles? If you can find records to verify that you received two MMR vaccines at some point in your life, then you are immune. If you are unsure, or can’t find your records, then a simple blood test, called rubeola antibody, can determine if you are immune. If you are not immune, then you should receive an MMR shot. Some groups, like healthcare providers and others at higher risk, need two MMR shots at least 28 days apart.
For those vaccinated in the 1960s, the situation is a bit more complex. Between 1963 and 1967, two different measles vaccines were used – one a killed vaccine, and the other a live vaccine. The killed vaccine proved ineffective in providing lasting immunity, while the live measles vaccine was effective. Those who received the killed vaccine cannot be assured of immunity. They would either need to have a blood test to check immunity, or be vaccinated with two doses of MMR at least 28 days apart.
Ironically, due to the tremendous success of vaccines such as MMR, many adults have never seen a case of measles. As a result, many are no longer aware of how serious the infection can be, and thus don’t fear it. This has led some parents, so-called “anti-vaxers,” to decline vaccination for their children. Many tout false or unproven beliefs that vaccines are somehow harmful. Quite to the contrary, health data overwhelmingly show that vaccines are truly lifesaving, with very minimal risk. This is certainly true of measles.
We can eliminate measles again from the United States. The only way is to make sure that almost all of us are immune. Elimination from the U.S. is not a “once and for all” reality, but a state that can only be maintained through ongoing vaccination. Lest we repeat the preventable tragedy of 2019, all of us must endorse universal vaccination to protect our own health, the health of our children, and of the community at large. This applies not only to measles, but to mumps, rubella, polio, tetanus, diphtheria, and other vaccine-preventable diseases that have tragically taken so many lives over the course of history.
Dr. Paul Kamitsuka is board certified in infectious diseases and is the hospital epidemiologist at New Hanover Regional Medical Center. He also serves as a clinical associate professor with the UNC School of Medicine.