Chikungunya virus is a mosquito-borne pathogen that causes an acute illness characterized by a sudden onset of fever and severe joint pain. This joint pain can be debilitating and may persist for weeks, months, or even years after the initial infection. Other symptoms can include headache, muscle pain, nausea, fatigue, and a rash. The virus is prevalent in tropical and subtropical regions, with outbreaks reported across Africa, Asia, the Americas, Europe, and islands in the Indian and Pacific Oceans. Given its widespread presence and the potential for severe, lingering symptoms, a vaccine represents a significant preventive measure against this viral disease.
How the Vaccine Works
The Chikungunya vaccine, known as IXCHIQ, is a live-attenuated vaccine, meaning it contains a weakened version of the virus. When administered, this attenuated virus replicates in the body but is not strong enough to cause the full-blown disease in most individuals.
This weakened virus stimulates the immune system to recognize Chikungunya. The body produces specific neutralizing antibodies and T-cells, which are then prepared to fight off a future infection by the wild-type Chikungunya virus, aiming to prevent illness or reduce its severity. In clinical trials, a single dose of IXCHIQ elicited Chikungunya-specific neutralizing antibody levels in nearly all vaccinated individuals, with sustained antibody titers for at least six months.
Who Can Get Vaccinated
The IXCHIQ vaccine is approved for individuals 18 years of age and older who face an increased risk of exposure to the Chikungunya virus, including travelers to outbreak areas or regions with recent transmission within the last five years.
The vaccine is contraindicated for specific populations. Individuals with compromised immune systems due to disease or medical therapies, such as those with hematologic cancers, receiving chemotherapy, or with severe HIV infection, should not receive this vaccine. A history of severe allergic reaction, such as anaphylaxis, to any vaccine component also prevents vaccination. While data on pregnant individuals are limited, vaccination is generally deferred during pregnancy; however, a healthcare provider might consider it if the risk of infection is high and unavoidable, weighing potential benefits against risks.
What to Expect After Vaccination
The IXCHIQ vaccine is administered as a single 0.5 mL dose by intramuscular injection. Common side effects reported after vaccination include tenderness at the injection site, headache, fatigue, and muscle pain. Other reported reactions include joint pain, fever, and nausea. These common side effects typically resolve within an average of two days.
Less common, but more severe, chikungunya-like adverse reactions, which can prevent daily activity or require medical intervention, occurred in about 1.6% of vaccine recipients in clinical studies. These reactions, which can include fever, joint pain, muscle pain, headache, or neurological symptoms, typically began around four days after vaccination and had a median duration of four days, though some prolonged reactions lasting at least 30 days were reported in a small number of individuals. Fainting can also occur with any injectable vaccine, so precautions are taken to prevent injury.
Vaccine Availability
The IXCHIQ vaccine has received regulatory approvals in several regions, making it the first and only licensed Chikungunya vaccine. The U.S. Food and Drug Administration (FDA) approved IXCHIQ in November 2023 for individuals 18 years of age and older who are at increased risk of exposure. The European Commission (EC) granted marketing authorization for the vaccine in Europe in July 2024, following a review by the European Medicines Agency (EMA).
Health Canada also approved the vaccine, and Valneva, the manufacturer, anticipates initial sales in Canada and Europe in the fourth quarter of 2024. Additional marketing authorization applications are under review, including one by the Brazilian Health Regulatory Agency (ANVISA), with potential approval expected in 2024, to broaden access in low- and middle-income countries. The EMA temporarily restricted use of IXCHIQ in people aged 65 years and older due to rare serious adverse effects resembling Chikungunya symptoms, including fever, malaise, confusion, and, in rare instances, encephalitis; however, this temporary restriction has since been lifted, with the recommendation that the vaccine be used in individuals of all ages where there is a significant risk of infection, after careful consideration of benefits and risks.