FDA and EMA Raise Safety Concerns Over Valneva's Chikungunya Vaccine

U.S. and European health regulators have identified serious safety issues with Valneva's chikungunya vaccine, Ixchiq, prompting recommendations to pause or restrict its use in older adults. The announcements come as a setback for the vaccine, which was approved by the FDA in November 2023 for the prevention of chikungunya virus in adults 18 years and older.

Safety Signals Trigger Regulatory Action

The U.S. Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) have recommended pausing the use of Ixchiq in adults 60 years and older following reports of serious neurologic and cardiac events. Similarly, the European Medicines Agency (EMA) has implemented temporary restrictions, prohibiting the vaccine's use in adults aged 65 and above.

These actions stem from post-marketing reports documenting 17 serious adverse events globally, including two fatalities. Six of these cases occurred in the United States. The affected individuals were between 62 and 89 years old, raising particular concern for the vaccine's safety profile in older populations.

Unexpected Adverse Reactions

While Ixchiq's label lists common side effects such as injection site reactions, headaches, fatigue, myalgia, and fever, the recent safety signals have revealed more severe and unexpected reactions. The FDA noted instances of "severe chikungunya-like adverse reactions that prevented daily activity and/or required medical intervention," which were not commonly observed during clinical trials.

Some of these severe reactions led to hospitalizations, with certain cases persisting for up to 30 days. These findings contrast sharply with earlier data from December 2024, which had indicated long-term durability of the vaccine's protection, with 96% of inoculated participants maintaining protective antibody levels three years post-vaccination.

Regulatory Response and Ongoing Investigations

As health authorities conduct in-depth reviews of the post-marketing data, the use of Ixchiq is being carefully managed. The FDA and CDC's pause recommendation for adults 60 and older in the U.S. is complemented by the EMA's more stringent restriction for those 65 and above in the European Union.

These precautionary measures affect a significant portion of the approximately 80,000 Ixchiq doses distributed worldwide. Meanwhile, younger adults below the specified age thresholds may continue to receive the vaccine, as current data suggest a more favorable risk-benefit profile in these populations.

The situation highlights the critical role of post-marketing surveillance in identifying rare but serious adverse events that may not be apparent in pre-approval clinical trials. It also underscores the importance of robust vaccine safety monitoring systems, a topic that has recently gained attention with Health and Human Services Secretary Robert F. Kennedy Jr. calling for reforms to the Vaccine Adverse Event Reporting System (VAERS).

As investigations continue, the pharmaceutical industry and regulatory bodies remain focused on balancing the need for innovative vaccines against emerging infectious diseases with the paramount importance of patient safety.