CDC Investigating Hospitalizations of 5 People Who Received Vaccine for Rare Chikungunya Virus

The FDA’s information on the vaccine says that ‘vaccination with IXCHIQ may cause severe or prolonged chikungunya-like adverse reactions.’

The Centers for Disease Control and Prevention headquarters in Atlanta on April 23, 2020. (Tami Chappell/AFP via Getty Images

The U.S. Centers for Disease Control and Prevention said it is investigating the hospitalizations of five people who recently received a vaccine for the chikungunya virus, which is transmitted via mosquitoes.

In a notice on Tuesday, the CDC said that the five hospitalizations occurred in people aged 65 and older and that they suffered cardiac or neurologic problems after receiving a vaccine known as IXCHIQ.

“This topic will be discussed at an upcoming meeting of the Advisory Committee on Immunization Practices (ACIP). Healthcare providers should discuss the benefits and risks of vaccination with individual travelers based on their age, destination, trip duration, and planned activities,” the agency said.

Chikungunya is a rare viral disease spread by infected mosquitoes that can cause joint pain and fever, circulating in subtropical and tropical areas. There have been outbreaks of the disease in the United States, namely in the years 2014, 2015, and 2016, but local cases have not been reported since 2019, the CDC says.

According to the CDC’s website, the IXCHIQ vaccine contains a live but weakened version of the chikungunya virus. The shot, made by Valneva, was approved by the U.S. Food and Drug Administration (FDA) in November 2023, described as “the first chikungunya vaccine” and for adults who are “at increased risk of exposure to chikungunya virus.”

The FDA’s information on the vaccine says that “vaccination with IXCHIQ may cause severe or prolonged chikungunya-like adverse reactions” and it lists contraindications such as an immune-compromising condition or an allergic reaction.

“Common adverse reactions following vaccination that occurred in [greater than 10 percent] of vaccinated persons in clinical trials included tenderness, headache, fatigue, myalgia, arthralgia, fever, and nausea,” the CDC said.

The chikungunya vaccine would have been discussed in an ACIP meeting scheduled for Feb. 26, according to a readout of proposed topics for discussion during that meeting. The meeting was postponed by the CDC earlier this week.

According to the agency, people who are traveling to countries or areas that have an elevated risk of transmitting chikungunya should “take steps to avoid” being bitten by mosquitoes.

“The risk for chikungunya for most U.S. travelers is low. However, some travelers are at increased risk for infection or more severe disease,” it said. “Factors to assess when considering use of chikungunya vaccine include the likelihood of exposure to chikungunya virus, a traveler’s risk factors for severe disease outcomes, and traveler preferences.”

Chikungunya causes fever and severe joint pain, often in the hands and feet. Other symptoms include headache, muscle pain, joint swelling, and a rash. The virus originated in mosquito populations in Africa, southern Europe, and Southeast Asia and reached islands in the Caribbean in 2013, the CDC said.

Most cases in the United States were found in people who had traveled to other countries, although there were a small number of cases in the Florida Keys in 2014.

“Dengue and Zika have similar symptoms to chikungunya, making chikungunya easy to misdiagnose,” the World Health Organization says on its website. It adds that “severe symptoms and deaths from chikungunya are rare and usually related to other coexisting health problems.”

The Associated Press contributed to this report.