What you need to know about measles

Although health officials declared measles eradicated in the U.S. nearly 20 years ago — thanks to a very effective vaccine — the highly contagious disease is back in the news.

Dr. Jyotu Sandhu, a family medicine doctor with Sharp Rees-Stealy Medical Group, answers common questions about the disease:

What does measles look like?
Measles, a viral respiratory illness, typically presents with a high fever, fatigue, cough, nasal congestion and conjunctivitis of the eyes, followed by a rash. The rash appears as flat, red spots that start on the head and neck and spread down the body to the trunk, arms and legs. Patients are considered contagious for four days before and four days after the rash appears.

Who's at greatest risk of getting measles?
People at highest risk of developing measles include infants and children under 5; unvaccinated people; pregnant women; and people with compromised immune systems, such as those with cancer and HIV. Additionally, some adults who only received one dose of vaccine as a child may have some susceptibility to the illness.

What are the health risks of measles?
Complications of having measles include ear and throat infection, pneumonia, diarrhea, swelling of the brain and death.

How does measles spread?
Measles is very contagious. One infected person will spread measles to 90% of the unvaccinated people around them. Measles is transmitted by direct contact with viral particles from an infected person who breathes, coughs or sneezes. The virus can remain in a room for up to two hours after the infected person leaves the area.

How does someone know if they have an immunity to measles?
You have an immunity to measles if you have one of the following:

• Written documentation of one or more doses of a measles-containing vaccine administered after 1968, on or after the first birthday for preschool-age children and for adults not at high risk

• Written documentation of two doses of measles-containing vaccine after 1968 for school-age children and for adults at high risk, including college students, health care personnel and international travelers

• Laboratory evidence of immunity by checking for antibodies in the blood

• A birthday before 1957, as you most likely were exposed to measles as a child and developed an immunity

How does the vaccine work?
After vaccination, the body’s immune system makes protective virus-fighting antibodies against the harmless vaccine virus. Measles vaccine protects against wild-type — or, naturally occurring — measles. If a vaccinated person is exposed to someone with measles, the body remembers how to fight off the wild-type virus because the vaccine trained the immune system.

Why are two vaccine doses recommended?
In 1989, measles outbreaks among vaccinated school-age children prompted the Advisory Committee on Immunization Practices, the American Academy of Pediatrics and the American Academy of Family Physicians to recommend a second dose of MMR (measles, mumps and rubella) vaccine for all children.

By 2000, there were no active cases. However, 2019 saw the highest number of measles diagnoses — nearly 1300 — since 2000.

Why did the CDC announce that some adults born between 1963 and 1981 might not be fully immunized?
In the decades before 1963, when a vaccine became available, nearly all children got measles by the time they were 15 years old. By 1968, an improved vaccine was made available in the U.S. and has been used since.

By 1981, the number of reported measles cases was 80% less than the previous year. Up to this point, children only received one dose of vaccine, so immunity status is uncertain. Adults who do not know the number of doses received can check their childhood vaccination record or talk with their doctor about whether their blood levels should be tested.

Can children and adults reach full immunity with a measles booster shot?
Although one can’t achieve “full” immunity, receiving two doses of the vaccine provides 97% immunity to measles. Adults born between 1963 and 1981 who have questions or concerns about measles immunity should talk with their doctor. Immunity levels can be confirmed with a blood test.

Learn more about family medicine; get the latest health and wellness news, trends and patient stories from Sharp Health News; and subscribe to our weekly newsletter by clicking the "Sign up" link below.