August 16, 2025

Surveillance for adverse events following use of live attenuated chikungunya vaccine, United States, 2024, and the associated public health response in 2024 and 2025.

SHSusan L. HillsNational Center for Emerging and Zoonotic Infectious Diseases RSRebekah SutterCenters for Disease Control and Prevention EMElaine R. MillerNational Center for Emerging and Zoonotic Infectious Diseases

Key Points

Twenty-eight adverse events were identified after the chikungunya vaccine's licensure, raising safety concerns.
Among the adverse events, six were serious neurological or cardiac cases in males aged 65 and older, highlighting a vulnerable group.
Post-licensure safety surveillance prompted updated guidance and a precautionary pause for vaccinations in older persons.
This response illustrates the importance of monitoring vaccine safety to protect public health, especially in at-risk populations.

Abstract

A live attenuated chikungunya vaccine (IXCHIQ) received licensure in the United States (US) for ≥ 18-year-olds in November 2023. Post-licensure safety surveillance identified 28 adverse events in 2024 among US persons, including six neurological or cardiac serious adverse events (SAEs) in males ≥ 65 years. In early 2025, providers were alerted, a precaution for older persons was issued and vaccine guidance was updated. In May, following 11 additional SAEs reported outside the US, use in older persons was temporarily paused until 6 August 2025.

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