What to Know about Measles Outbreaks in the US: Understanding the Impact and Urgency of Vaccination

(CTN News) – Paul Offit, a pediatric infectious disease doctor, has not been vaccinated against measles. Like many of his colleagues, he contracted the virus as a child in the 1950s, about a decade before a vaccine was developed.

At the time, the disease was highly contagious and potentially lethal, affecting an estimated three to four million Americans annually. Offit has been immune since then and is expected to remain so for the rest of his life.

The vaccine is critical for people who have not experienced the full-body rash, bulging eyes, and a slew of other unpleasant symptoms of measles to develop a lifelong immunity to the disease. Measles was declared eradicated in the United States in 2000, thanks to the broad use of the two-shot vaccine schedule in the 1990s, which reduced disease transmission.

This year, the U.S. Centers for Disease Control and Prevention recorded 58 measles cases in outbreaks spanning 17 states, equal to the total number of infections reported in 2023. As of last week, the following states have documented measles cases in 2024: Arizona, California, Florida, Georgia, Illinois, Indiana, Louisiana, Maryland, Michigan, Minnesota, Missouri, New Jersey, New York, Ohio, Pennsylvania, Virginia, and Washington.

The CDC has not reported any deaths, and some outbreaks remain active. The outbreak in Chicago has led to a joint response from the city’s department of public health, the CDC, and local health centers to isolate infected individuals and vaccinate those who are susceptible to the disease. At least 15 cases have been reported, including several from a migrant shelter in the Pilsen neighborhood.

Last month, Florida reported measles infections in numerous pupils at an elementary school in Miami. The outbreak received global attention after the state’s surgeon general, Joseph Ladapo, issued a public statement allowing unvaccinated children to attend school despite the risk of exposure.

The Florida Department of Health reports that no measles infections have been detected at the school since February 16, but does not disclose the number of cases in the epidemic. The department declined to respond to Scientific American’s request for comment.

Despite 95 percent herd immunity, there is still some measles transmission expected annually. However, the high number of infections so early in 2024 has some public health experts worried about what this means for the rest of the year and how vaccine misinformation and disinformation, compounded by COVID, may be influencing vaccination rates.

“During the pandemic, there were obviously a number of people who didn’t like being mandated to receive COVID vaccines, and now that mindset has spilled over into the [measles] vaccine,” says Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia. “But people can forget that measles is exponentially more contagious than COVID…, and it’s a nightmare.”

Measles is an airborne respiratory disease that spreads when an infected person breathes, coughs, sneezes, or touches surfaces. Symptoms usually appear 10 to 14 days after initial exposure. They include a red, splotchy rash on the face and neck, fever, puffy and watery eyes, and symptoms similar to the common cold.

Anyone can get measles, but children—especially those two years old or younger with a growing immune system—are the most vulnerable.

There is no specific cure for measles, and in some cases, the disease can cause ear infections, diarrhea, pneumonia, and encephalitis (brain swelling that can lead to permanent disability); it can also be fatal.

In the early 1900s, the U.S. reported an average of 6,000 measles-related deaths annually. By the mid-century, advances in medical therapies had reduced complications and mortality.

Furthermore, people’s natural antibodies, which can be passed down from mothers to their babies and give short-term protection, reduced the frequency of baby illnesses. However, almost everyone had contracted measles by the age of 15. Approximately 48,000 persons were hospitalized each year, with 400 to 500 deaths.

“As someone who had a natural measles infection, I can tell you that it’s seriously no fun,” Offit said. “Now they ask old people like me to come down to the emergency room to look at people with fever and a rash because I’ve seen so much of it, and I can tell them within 30 seconds whether or not it’s measles.”

Biochemist John Enders and physician Thomas Peebles developed the first measles vaccine, which was licensed in 1963, after successfully extracting and isolating the virus from an afflicted 13-year-old boy.

In 1968, microbiologist Maurice Hilleman perfected the shot, which was then distributed throughout the United States. This type of the vaccination, known as MMR, protects against two more infectious diseases, mumps and rubella, and is the most widely used today.

The MMR vaccination is 93% effective in preventing measles, and its usage has significantly reduced infections. However, a significant number of outbreaks continued to occur as of 1989, so U.S. public health organizations began recommending that people receive one dose of the vaccine around their first birthday and a second dose when they are four to six years old, providing 97 percent effective lifetime protection.

In the early 2000s, however, MMR vaccination rates in the United States fell after British physician Andrew Wakefield published scientific research indicating that the vaccine could cause autism.

His study was disproved after further review, but not before instilling dread and distrust in the United States and abroad. “It’s really hard to unring a bell,” Offit explains. “Once people are scared of something, it’s tricky to ease them, and so a bunch of measles started showing up again around 2004 and 2005.”

MMR vaccination rates have progressively increased since then, and most public and private schools now require children to be vaccinated before enrollment.

However, measles cases are reappearing over the country, and Offit is concerned that a surge in antivaccine attitude that began during the COVID pandemic is partly to blame.

The most common reasons parents choose to opt their child out of MMR and other vaccine requirements are religious or medical reasons, while some jurisdictions allow parents to use personal beliefs as a grounds for exemption.

A November 2022-2023 CDC study found that vaccine exemption rates among kindergartners increased to 3%, a 0.4 percent increase from the previous year. In 10 states, more than 5% of kindergartners had exemptions.

According to Jerne Shapiro, an instructional assistant professor of epidemiology at the University of Florida, coverage varies widely across counties and municipalities, and each private school may have its own specific immunization criteria.

Measles outbreaks can also occur when infected people travel to the United States from other countries. According to Shapiro, if sick travelers come into touch with unvaccinated or immunocompromised Americans, secondary measles cases may develop.According to Offit, one individual with measles infects 12 to 18 others on average.

With measles outbreaks likely to increase, Offit and Shapiro urge Americans, particularly spring break travelers, to check their MMR vaccination status and seek vaccine and outbreak information only from physicians and government-certified sources such as the CDC, World Health Organization, and National Institutes of Health.

“There is so much misinformation about vaccines in general,” Shapiro said. “But this vaccination has been used for decades upon decades. Most of us are lucky enough not to be familiar with the appearance of the majority of vaccine-preventable diseases, which we often take for granted.”