Chikungunya Outbreak in China Spurs U.S. Travel Alerts

An outbreak of chikungunya virus has emerged mostly in southeastern China. The news comes about two months after the Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) recommended that older adults pause taking one of the two vaccines used to prevent the infection.

More than 7,000 cases were reported in China as of Wednesday, though new cases seem to be decreasing, the Associated Press reported. Foshan, an area in Guangdong Province northwest of Hong Kong, has been hit especially hard.

The vaccine is sometimes administered before traveling to certain tropical and subtropical areas where the mosquito-borne virus chikungunya spreads. An infection with the virus is rarely fatal but can result in persistent joint pain. About 200 cases of chikungunya were reported in the U.S. in 2024; all of them were travel-associated. The Ixchiq vaccine is a live vaccine that has been linked to serious adverse events in older individuals who received it. The CDC issued a Level 2 travel alert for Guangdong Province on Aug. 1, which references the concerns about the Ixchiq vaccine and notes that people over 60 should not receive that shot.

Scott Mahan, M.D., an infectious disease doctor and assistant chief of medicine for education and research at Charles George VA Hospital in Asheville, North Carolina, says he would be hesitant to use Ixchiq in people over age 60 unless he had no other options. The other virus particle vaccine called Vimkunya seems safe for all ages and would be his first choice, Mahan says. ​

Why are there concerns about the live chikungunya vaccine?  

Health officials say these serious side effects, which include neurologic and cardiac events, did not appear in the two clinical trials testing the vaccine’s safety and efficacy but have since been reported to the Vaccine Adverse Event Reporting System, comanaged by the FDA and CDC. As of May 7, 17 serious adverse events, including two that resulted in death, had been reported in individuals age 62 to 89, according to the FDA. "This is all very new information, and the underlying reason is still not known,” says William Schaffner, M.D., an infectious disease expert and professor of preventive medicine at Vanderbilt University Medical Center.

“But it is known that chikungunya itself disproportionately causes serious illness in older persons, and this vaccine, Ixchiq, is a live attenuated vaccine,” meaning it contains a weakened version of the virus. The FDA says the vaccine may cause symptoms that are similar to symptoms experienced by people with chikungunya disease. “The going thought is that somehow this tamed virus is not tamed enough for use in older persons,” Schaffner says.

The vaccine was approved in the U.S. in 2023 for adults 18 and older; approximately 80,000 doses of Ixchiq have been distributed globally.

The FDA says it will conduct an updated benefit-risk assessment for the use of Ixchiq in adults 60 and older. European health regulators are also reviewing the issue.