The Centers for Disease Control and Prevention is immediately sending experts in response to a request from the Samoan government for assistance with a measles outbreak that has sickened 2,437 people and killed 32, mostly children, U.S. officials said Tuesday.

The CDC is providing technical assistance with tracking and monitoring of cases and vaccination campaigns, according to Robert Linkins, a CDC expert on global immunization. Two CDC experts are expected to be on the ground shortly, U.S. officials said. Vaccination rates in Samoa are among the lowest in the world, and the country has been the target of anti-vaccine activists.

The measles outbreak was declared Oct. 16 and is spreading rapidly throughout the island with unprecedented severity, CDC officials said. Children under 5 account for nearly half of cases.

In late November, the Pacific nation closed schools nationwide and indefinitely banned children younger than 17 from public gatherings. The number of measles cases represents more than 1 percent of the population of nearly 200,000.

Measles is one of the most contagious diseases known. It can cause serious health complications, such as pneumonia or encephalitis, and death. Two doses of the vaccine for measles, mumps and rubella are 97 percent effective in preventing measles.

The high number of recent infections indicates that the Samoan crisis is far from over: The Health Ministry said 243 cases were reported in the previous 24 hours.

“It does not appear, from the numbers we’ve been seeing, that it has peaked yet,” Helen Petousis-Harris, a vaccine safety expert at the University of Auckland in New Zealand, told The Washington Post. “This is really severe.”

The average mortality rate for measles in a country with Samoa’s income level is about 2 per 100 cases, she said.

Twenty-eight of the 32 deaths were children under 5. More than 90 percent of those recently admitted to hospitals were children.

“The children are quite ill,” Leausa Take Naseri, the Health Ministry’s director general, told reporters Friday. “Our ICUs have been dominated by these children.”

Despite the evidence, the anti-vaccination movement is gaining strength. (Luis Velarde/The Washington Post)

Children who survive measles infections can have future health problems. The virus may provoke what is called immune amnesia, destroying antibodies the immune system developed against other germs. And a complication known as subacute sclerosing panencephalitis, or SSPE, may emerge from dormancy years later. The odds of developing SSPE are low, about 1 in 600, but it is fatal.

Samoa’s vaccination rate lags behind that of other Pacific island countries.

“This is a reflection of a whole lot of factors. People are not so confident in their health system,” Petousis-Harris said. “They have quite a culture of anti-vaccine sentiment there as well.”

Anti-vaccine activist Robert F. Kennedy Jr., a nephew of President John F. Kennedy, visited the country in June, appearing next to officials at Samoan independence celebrations. His visit was “for a program that is not government-related,” an official in the prime minister’s department told Samoan news media at the time.

Kennedy has asserted that vaccines cause autism, a claim disproved by extensive research. Members of the Kennedy family have publicly criticized him for helping “spread dangerous misinformation.”

An Instagram photo shows Kennedy embracing the Australian Samoan anti-vaccine activist Taylor Winterstein in Samoa on June 4. “I am deeply honored to have been in the presence of a man I believe is, can and will change the course of history,” Winterstein wrote in the caption, adding hashtags #makinginformedchoices #investigatebeforeyouvaccinate.

Winterstein, who is married to a rugby star and has 25,000 Instagram followers, planned to hold an anti-vaccine workshop in Samoa as part of an international tour. She sold $200 tickets for the meetings, titled “Making Informed Choices.” After opposition from Naseri and other health officials, she canceled the anti-vaccine seminar scheduled for the Samoan capital, Apia.

Winterstein and Kennedy said they met by chance in Samoa while staying at the same resort in June. “The encounter with the Winterstein family was purely serendipitous,” Kennedy said.

A person from the U.S. embassy was also present. “The reported meeting amongst individuals known for their anti-vaccine views did include a local staffer of the U.S. embassy, but these meetings were conducted on his own time in his capacity as a private citizen and do not in any way reflect the position of the embassy nor the U.S. government,” said a State Department official.

Kennedy’s charity shared a Nov. 19 letter he wrote to Samoan Prime Minister Tuilaepa Sailele Malielegaoi, in which Kennedy encouraged officials to examine the MMR vaccine. “To safeguard public health during the current infection and in the future, it is critical that the Samoan Health Ministry determine, scientifically, if the outbreak was caused by inadequate vaccine coverage or alternatively, by a defective vaccine,” he wrote.

Meticulous scientific studies over the past two decades have repeatedly disproved links between autism and vaccines, including immunizations against measles, mumps and rubella. British officials stripped the medical license from Andrew Wakefield, the author of a 1998 report that claimed an association between autism and vaccines, after concluding that he had committed scientific fraud.

The World Health Organization estimated that in 2018, only 31 percent of infants in Samoa received the measles vaccine, a drop from 60 to 70 percent in previous years. The WHO attributed the extremely low rate in part to a public health scandal: Last year, two infants in Samoa died within hours of receiving the MMR vaccine. The country temporarily halted its vaccine program, but the vaccine did not cause the deaths. Two nurses improperly mixed the vaccines with a liquid muscle relaxant instead of water. The pair were sentenced to five years in prison for manslaughter.

In several Facebook posts in July and August 2018, Children’s Health Defense, the advocacy group that Kennedy founded, questioned the safety of the vaccines the infants received. The charity did not update the posts to explain the nurses’ error to its audience.

“The public were never told, for months, that it wasn’t the vaccine that killed the babies, which really was the most important message,” Petousis-Harris said.

The Health Ministry embarked on a vaccination campaign in late November and, within five days, immunized more than 17,000 people. Vaccinations are compulsory for children from 6 months to 19 years and for nonpregnant women between 20 and 35.

Mandatory vaccines and isolation can curb a measles epidemic, Petousis-Harris said, but such responses work best when swift. “Unfortunately, Samoa implemented those options very, very late.”

Measles, once declared eliminated in the United States, spread rapidly in 2019. Worldwide, there were more measles cases in the first six months of 2019 than in the initial six months of any year since 2006, according to WHO data.

The virus has afflicted several countries in Southeast Asia, so severely in the Philippines that overburdened hospitals tended to patients in parking lots. Unvaccinated Philippine travelers spread the disease to New Zealand, Petousis-Harris said, from where it spread to Samoa. Travelers from Samoa took it back to New Zealand. “It’s been seeded throughout the Pacific,” she said.

American Samoa, the U.S. territory that is part of the island chain that includes Samoa, declared measles an urgent public health priority in October. It requires proof of immunization for travelers from neighboring countries.

Several countries, including Australia and New Zealand, which is contending with its own measles outbreak, have sent nurses and vaccines to Samoa. By mid-November, the United Nations Children’s Fund delivered 110,500 doses of measles vaccine.

Dalton Bennett contributed to this report. This report has been updated.

Read more: