In a significant turn in the global fight against chikungunya, U.S. health authorities have urged patients and providers to hold off on using the vaccine Ixchiq—the only FDA-approved protection against the mosquito-borne virus—while safety evaluations are conducted. On Friday, both the U.S. Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) issued a joint safety communication, highlighting “postmarketing reports of serious adverse events, including neurologic and cardiac events,” tied to the vaccine.

Approved just six months ago in November 2023, Ixchiq marked a hopeful milestone for travelers and residents at risk of chikungunya infection, particularly in tropical and subtropical regions. But with over 80,000 doses administered globally and troubling reports now emerging, health officials have paused U.S. distribution while an updated benefit-risk assessment is conducted, especially for those aged 60 and older.

Elderly Population Under the Microscope

So far, 17 serious adverse events have been reported globally among individuals over 62 years old, including two deaths. Six of these cases occurred in the United States, though it remains unclear whether the deaths were U.S.-based. Officials emphasized that these events are not yet proven to be caused by the vaccine—but the correlation is serious enough to warrant further investigation.

“The reported adverse events may not be causally related to vaccination,” the FDA noted in its advisory. Still, the risk profile for older individuals is being reevaluated in light of these findings.

The Virus Itself: Dangerous, But Rarely Deadly

Chikungunya is spread by the Aedes mosquito—the same genus responsible for dengue and Zika outbreaks. Infected individuals experience symptoms similar to dengue fever, including sudden high fever, rash, headaches, and debilitating joint pain that can linger for months. Although the virus rarely causes death, it can be severely disabling, particularly in older adults or those with underlying conditions.

So far in 2025, the European Centre for Disease Prevention and Control has documented approximately 80,000 chikungunya cases and 46 related deaths across 14 countries and territories. No new cases have been recorded on mainland Europe, but outbreaks have been prevalent in the Caribbean, Africa, and parts of Asia.

One Vaccine, Many Questions

Ixchiq is a single-dose, live-attenuated vaccine developed specifically for adults at increased risk of exposure, such as international travelers and residents in outbreak-prone areas. The live nature of the vaccine, while often effective in stimulating immune protection, can also pose risks—especially for immunocompromised individuals or older adults whose immune systems may respond unpredictably.

Adding another layer of complexity, research has shown that mosquitoes can transmit multiple viruses simultaneously. In fact, co-infections of chikungunya and Zika have been recorded in the past, with some leading to fatal brain infections. This amplifies the urgency for a reliable and safe vaccine—but not one that trades one danger for another.

A Flashback to Earlier Outbreaks

The virus first gained global attention in late 2013, when chikungunya was detected in the Americas and quickly spread across the Caribbean, eventually reaching Georgia and North Carolina through travelers returning from Cuba. Since then, sporadic outbreaks have continued, making preventive measures and vaccination a public health priority.

Politics and Public Trust

The timing of this advisory also intersects with a broader scrutiny of vaccine programs led by U.S. Health and Human Services Secretary Robert F. Kennedy Jr., a controversial figure known for questioning the safety of long-established vaccines. While this specific investigation is being conducted based on adverse event reports, the larger conversation around vaccine safety, transparency, and public trust remains as critical as ever.

What Now?

For now, U.S. patients are advised to hold off on receiving Ixchiq until further notice. The FDA and CDC stress that they are continuing to monitor the situation closely and will share updated guidance as soon as their review is complete. Travelers planning to visit regions where chikungunya is active should consult healthcare professionals for alternate preventive strategies, including mosquito repellents, protective clothing, and staying in screened or air-conditioned areas.

In the battle between virus and vaccine, safety remains the top priority—and the pause on Ixchiq reflects a necessary step toward ensuring that prevention does not come at too high a cost.