Here’s what you need to know

More than 160 measles cases have been reported across nine states this year, with one death and more than 30 patients needing hospitalization, according to a Centers for Disease Control and Prevention tracker.

Of those cases, 95% have occurred in patients either not vaccinated for the disease or who have an unknown vaccination status. Only 5% of cases were people with one or two doses of the vaccine that defends against measles, mumps and rubella.

What’s worrying is that “outbreaks are happening in the context of increased rates of vaccine hesitancy and decreased rates of immunity,” said Dr. Patrick Jackson, an associate professor of medicine at the University of Virginia School of Medicine who specializes in infectious diseases.

“It’s an incredibly contagious virus, so we rely on high levels of vaccination to contain the spread,” he said. “That makes me worry about when we’ll have a lower vaccine level and see more sustained transmission of measles.”

First introduced in 1963, the vaccine virtually eliminated the disease in the U.S. by 2000. There have been occasional case clusters since, usually involving an unvaccinated person being exposed to measles while traveling, Jackson said.

In 2019, 649 cases were confirmed in New York’s Williamsburg neighborhood. An estimated 93% of the cases were in the Orthodox Jewish community after an unvaccinated child was exposed to measles while traveling abroad. The overwhelming number of cases were in young, unvaccinated people, with 81.2% of patients under 18.

“If people have received appropriate measles vaccination, we believe immunity is lifelong and there is no need to pursue additional protection,” Jackson said.

Measles, an airborne illness, is extremely infectious. Before the measles vaccine became available, the illness killed between 400 and 500 people in the United States each year and hospitalized an estimated 48,000 every year, according to CDC data.

The World Health Organization declared measles eliminated in the U.S. in 2000; both North and South America were declared free from the virus in 2016. But, with the new outbreaks across the country, the Pan-American Health Organization warns the eliminated status may be at risk.

“This is a disease that should not be a thing anymore in this country,” Dr. Taison Bell, UVA’s acting chair of medicine, said. “We have a vaccine that prevents it and the ability to eradicate it.”

The recommended protection is two doses of the vaccine, which is 97% effective at preventing measles. The Pan-American Health Organization recommends that 95% of the population should be vaccinated, with a focus on children and young adults.

Roughly a third of cases reported this year by the CDC were in children under 5, and almost half of cases were in children 5 to 19 years old.

Others at risk are health care workers, immunocompromised people, pregnant women and unvaccinated children. Infants are at higher risk because they cannot get vaccinated before their first birthday.

“There are some higher risk categories but, for most people, if you’re fully vaccinated, you should have nothing to worry about,” Bell said. “Even though measles is highly infectious, it doesn’t mutate much like COVID or the flu, so the vaccine is very effective and gives lifelong immunity.”

UVA requires incoming students to show proof of vaccination against measles, with few exemptions, including a religious exemption, Bell said.

“We’re a reasonably well-vaccinated population,” he said.

Doctors began recommending two doses of the vaccine in 1989, according to Bell. He said anyone vaccinated before that year should check to see if they should go back in for their second dose.

“I was actually in this category,” he said. “It’s never too late to get vaccinated.”