Chikungunya Vaccine

Adults ≥18 years at increased risk of chikungunya virus exposure: travelers to endemic/epidemic areas in the Americas, Africa, South/Southeast Asia, and Indian Ocean islands. Laboratory workers handling chikungunya virus. Residents of areas with active or recent outbreaks. Particularly relevant given geographic expansion of Aedes aegypti and Aedes albopictus vectors into temperate regions.

Severe allergic reaction (anaphylaxis) to a previous dose or any component. Immunocompromised individuals including those on immunosuppressive therapy (live attenuated vaccine). Pregnancy — avoid conception for at least 30 days after vaccination. Moderate to severe acute illness (defer until recovery).

Very common (≥1/10): headache (31%), fatigue (28%), myalgia (24%), arthralgia (16%), injection site pain (13%), fever (14%), nausea (10%). Common (1–10%): injection site erythema, swelling, malaise. Transient chikungunya-like symptoms may occur 3–14 days post-vaccination (joint pain, fever) — generally mild and self-limiting. Rare: severe arthralgia requiring medical attention.

Single 0.5 mL dose, intramuscular injection in the deltoid muscle. No booster currently recommended — durability of immune response beyond 2 years under study. Administer ≥14 days before potential exposure. Store at +2°C to +8°C, protect from light.

Phase 3 trial (NCT04546724): 98.9% seroconversion rate (neutralizing antibodies ≥PRNT80) at day 28 post-vaccination. 263.5 GMT fold-rise from baseline. Antibody persistence: ≥96% seropositive at 6 months, data emerging for 12–24 months. No efficacy trial against clinical disease (approved based on immunogenicity under Accelerated Approval pathway).

Do not administer concurrently with other live vaccines unless data supports co-administration — general recommendation of same day or ≥4 weeks apart. No data on co-administration with travel vaccines (yellow fever, Japanese encephalitis). Inactivated vaccines can be given at any interval. Immunoglobulins may reduce immune response.

Pregnancy: Ixchiq® (live attenuated) is contraindicated during pregnancy. In animal studies, chikungunya vaccine virus was detected in fetal tissues. Women of childbearing potential should avoid pregnancy for at least 30 days after vaccination. If a pregnant woman is inadvertently vaccinated, she should be counseled about the potential risks. Natural chikungunya infection during pregnancy, particularly near delivery, can cause severe neonatal disease — risk–benefit assessment for travel to highly endemic areas should be discussed.

Breastfeeding: There are no data on the presence of Ixchiq® vaccine virus in human milk, its effects on the breastfed infant, or its effects on milk production. As a live attenuated vaccine, a theoretical risk of vaccine virus transmission to the infant via breast milk exists. The decision to vaccinate breastfeeding women should consider the risk of chikungunya exposure, the benefits of breastfeeding, and the potential risks to the infant. Consult with a healthcare provider for individual assessment.

Pediatric use: Ixchiq® is approved for adults aged ≥18 years only. Safety and efficacy in children and adolescents under 18 have not been established. Pediatric clinical trials are ongoing. Children traveling to chikungunya-endemic areas should rely on mosquito bite prevention measures (DEET-containing repellents approved for children ≥2 months, permethrin-treated clothing, bed nets). Chikungunya in neonates (peripartum transmission) can be severe, including encephalopathy and hemorrhagic complications.

Older adults (≥65 years): Ixchiq® is approved for adults ≥18 years without an upper age limit. Older adults traveling to chikungunya-endemic areas may benefit from vaccination as chikungunya infection in the elderly is associated with more severe and prolonged joint symptoms (chronic arthralgia lasting months to years). Immunogenicity data in adults ≥65 suggest adequate seroconversion rates, though antibody titers may be lower than in younger adults. As a live attenuated vaccine, it is contraindicated in immunocompromised older adults.

Not approved for individuals <18 years (studies ongoing in pediatric populations). Transient arthralgia may be more pronounced in older adults and persons with pre-existing joint conditions. Avoid pregnancy for ≥30 days post-vaccination. Breastfeeding: insufficient data, assess risk-benefit. Immunocompromised: contraindicated (live vaccine).