Measles was declared eliminated from the United States in 2000, by the World Health Organization (WHO) due to the success of vaccination efforts. However, it continues to be reintroduced—especially when unvaccinated people travel out of the United States to places where measles is present. Anti-vaccination sentiment continues to exacerbate the reemergence of measles outbreaks.

Measles is one of the most contagious infectious diseases. If not immunized, a person exposed to someone with measles has a 95% chance of becoming infected. During the early stage of an outbreak in an unvaccinated population, each infected person spreads the disease to an average of 12 to 18 other people. The recommended measles vaccination protocol is to receive two doses, at least one month apart. One dose of the vaccination is 93 percent effective at preventing measles, while two doses is 97 percent effective.

The United States has experienced variable trends in measles outbreaks in the 21st century, with major outbreaks occurring in 2014–2015, 2019, and in 2025–2026. In 2025, the CDC reported 2,289 confirmed cases across 45 jurisdictions and 49 separate outbreaks. In July 2026, the U.S. Centers for Disease Control and Prevention had logged 2,318 cases of measles thus far in 2026, which meant it was the worst year for measles in more than three decades. Experts say cases likely are significantly undercounted as many go unreported.

Since 2000, the largest single outbreak in the United States has been the 2025–2026 South Carolina measles outbreak with 997 total cases as of April 2026.

The vast majority of people infected in the 21st century were not vaccinated and lived in close-knit communities where the immunization rate is lower than average. There is concern that the WHO may rescind the US's measles elimination status.

The incidence of measles in the United States has reached its highest level in three decades, with 2,371 cases documented in July 2026. History

Before the vaccine was available in the United States, the Centers for Disease Control and Prevention (CDC) estimated that about three to four million were infected each year, of which approx. 500,000 were reported, with 400 to 500 people dying and 48,000 being hospitalized as a result. The last major outbreak was before the disease was eliminated, and occurred from 1989 to 1991. During this outbreak, 123 people died, the majority of whom were preschool children.

In the United States on average, two or three out of every 1000 children infected will die, and one will develop complications that often result in permanent brain damage.

The 2019 outbreak prompted President Donald Trump to shift away from his previous goal of spacing out vaccinations, and to insist that parents must vaccinate their children, stating "They have to get the shots. The vaccinations are so important". Surgeon General Jerome Adams drew a connection between states with vaccine exemptions and higher risks of outbreaks, and advised health officials on ways to encourage vaccination.

The 2025 outbreak began soon after Trump's inauguration for his second term as president and the subsequent appointment of Robert F. Kennedy Jr., a promoter of vaccine misinformation, as the Secretary of Health. Kennedy initially downplayed the outbreak, describing it as "not unusual". In 2025 the US had 2,012 measles cases, its highest since 1992 when it reported 2,200 cases.

An April 2025 study estimated that 51.2 million measles cases will occur over the next 25 years due to the decline in childhood vaccination.

Yearly cases of measles in the United States 2000–2026YearCases2000852001116200244200356200437200566200655200743200814020097220106320112202012552013187201466720151912016862017120201838120191,2742020132021492022121202359202428520252,2892026 (to date)3,887

Major outbreaks 2015 In a 2015 measles outbreak, 147 cases were linked to exposure at Disneyland in California. Following this outbreak, California changed its vaccination laws to only allow vaccination exemptions for those with medical conditions.

In 2019, cases were reported in 23 states, and the total number of reported cases (764) reached the highest number in 25 years by April. More than 500 of these cases were people who were not vaccinated against measles, and another 125 had an unknown vaccination status. The bulk of those infected were from the Orthodox Jewish communities in and around New York City.

2018 New Jersey outbreak The Centers for Disease Control and Prevention (CDC) declared an outbreak in New Jersey in 2018. 30 of the 33 confirmed cases were in Ocean County. It was determined that measles was contracted by a person who traveled to Israel and spread the virus upon returning to New Jersey.

2019 California outbreak From January to April 2019, 21 cases of measles were reported in California. The CDC published a summary of one outbreak caused by an unvaccinated teenager traveling to England. During the 2019 resurgence, two California universities, Cal State Los Angeles and University of California, Los Angeles, had to quarantine over 300 students and faculty.

2019 Pacific Northwest outbreak

The areas surrounding Vancouver, Washington, namely in Clark County, experienced an outbreak of measles in late 2018 and early 2019. The area was referred to as an "anti-vaccination hotspot" and the vaccination rate was 78%, which is too low for herd immunity. Oregon had reported that four residents have contracted measles due to the outbreak in neighboring Clark County.

As of April 2019, 74 confirmed cases of measles had been reported to the health department. More than half of those who fell ill were under the age of 10, and 70 of them had not been vaccinated or had unknown vaccination status. The remaining three people had received one dose of the measles vaccine.

In response to the outbreak, Representative Paul Harris proposed a measure that would remove the ability for parents to refuse any of the required childhood vaccines for philosophical reasons, otherwise keeping medical and religious exemptions. The bill was later amended to limit exemptions for the measles, mumps, rubella vaccine (MMR) vaccine. Children would not be allowed to attend public or private schools or day-care without evidence of vaccination or approved exemption documents. The bill was passed in April 2019.

2019 New York outbreak

New York experienced outbreaks in New York City and Rockland County in 2018 and 2019.

Between October 2018 and April 2019, 423 confirmed cases of measles were reported in New York City. The areas of Williamsburg and Borough Park, two Brooklyn neighborhoods with a high concentration of Orthodox Jews, have been most heavily affected. In response to the outbreak, Mayor Bill de Blasio declared a state of emergency and ordered mandatory vaccinations in the neighborhoods corresponding to the ZIP codes 11205, 11206, 11211, and 11249. It required that everyone living or working in the neighborhood who is more than six months old receive a vaccination or be subject to a $1,000 fine. Prior to the order, the health commissioner had required schools and day care centers in the area deny service to unvaccinated students to prevent the disease from spreading. In April, city officials ordered the closure of a preschool that refused to cooperate with requests for vaccination information.

From October to April, 153 cases of measles were confirmed in Rockland County, New York. Despite 17,000 doses of the MMR vaccination being given, the vaccination rate of children in the area was 72.9 percent as of April.

In December 2018, public health officials in Rockland County banned unvaccinated students from attending school. Parents of 42 students at Green Meadow Waldorf School, a private school, sued the Rockland County health department, but a judge denied the request to overturn the order. According to the health department, Green Meadow Waldorf School had a 56% vaccination rate. Waldorf schools have been identified as having higher noncompliance with measles vaccination programmes.

In March 2019, a flight attendant flew from NYC to Tel Aviv, Israel. Passengers on the flight were informed several days later that the woman had developed measles encephalitis and was in the intensive care unit (ICU) on a ventilator. The Israeli Ministry of Health reported that the woman may have been exposed in New York or in Israel. According to Emma Green the identification of the outbreak with the Jewish community led some leaders in the community to see a corresponding rise in expressions of antisemitism, although Hamodia and other Jewish thought leaders were encouraging vaccinations.

In April 2019, a state of emergency was declared in Rockland County, and unvaccinated children were barred from public places for 30 days. Parents of unvaccinated children that did not abide by this condition faced up to six months in jail or a $500 fine. A judge later lifted this ban, saying that the outbreak did not qualify for an emergency order. That month, New York began considering legislation to join the seven states and Washington, D.C. that allow children 14 years of age and older to seek vaccination without parental consent.

In June 2019, New York enacted a law repealing religious and philosophical exemptions for vaccination.

2019 Michigan outbreak A man from New York traveled to Michigan in March 2019, while unknowingly infected with measles. Health officials reported that he spread the virus to 38 people there. Because he was fundraising for Orthodox Jewish charities, he visited several synagogues each day while there. The man believed that he was immune to measles because he had it as a child.

2024 Florida outbreak A measles outbreak in Florida began in February 2024, at Manatee Bay Elementary School in Broward County. The State Surgeon General of Florida, Joseph Ladapo, addressed a letter to parents amid the outbreak, acknowledging the "normal" recommendation that unvaccinated children stay home, but stating his department was "deferring to parents or guardians to make decisions about school attendance." Ladapo's advice contradicts CDC guidance, which suggests that anyone not previously infected with measles or immunized against the disease observe a 21-day quarantine. On March 8, the Broward public school district declared the outbreak had ended on March 7.

Katelyn Jetelina and Kristen Panthagani referred to Ladapo's advice that children without immunization to measles could continue attending school after exposure as "unprecedented and dangerous". Leana Wen characterized Ladapo's decision as "outrageous" due to the danger posed by measles.

2024 Chicago outbreak In March 2024, the Chicago Department of Public Health declared it had detected two measles cases. The two measles cases were Chicago's first since 2019. The cases were detected in a migrant shelter in the Pilsen neighborhood at 2241 S. Halsted Street.

More cases at the shelter were reported the week of March 10. On March 12, a Centers for Disease Control and Prevention team arrived in Chicago to assist with the outbreak. On March 13, the Chicago Department of Public Health announced that all residents of the shelter able to receive a vaccine had received one. On March 14, two cases were reported in Chicago Public Schools, Cooper Dual Language Academy and Armour Elementary, bringing the total cases in the city to 10. On March 15, Chicago announced it would require migrants at city shelters receive the MMR vaccine. As of March 15, there were 12 cases of measles in the city.

2025 Southwest outbreak