FDA and CDC Advise Caution on Chikungunya Vaccine Use in Older Adults

Understanding the Recent Advisory on the Ixchiq Vaccine

Chikungunya is a mosquito-borne viral illness that has re-emerged as a global public health concern. Transmitted mainly by Aedes aegypti and Aedes albopictus mosquitoes—the same species responsible for dengue and Zika—the virus is spreading rapidly due to climate change, urbanization, and international travel.

In response to growing case numbers, a newly approved vaccine offered hope for prevention. However, in May 2025, U.S. health authorities issued an important safety advisory for older adults, prompting renewed discussion around vaccine use, risk assessment, and alternative prevention strategies.

Global Chikungunya Situation: A Growing Health Threat

Between January and early June 2025, more than 220,000 chikungunya cases and approximately 80 deaths were reported across 14 countries. The Americas accounted for the majority of infections, with Brazil reporting the highest number of cases, followed by Argentina, Bolivia, and Peru.

Although mainland Europe did not record local transmission, significant outbreaks occurred in French overseas territories, particularly Réunion Island and Mayotte, both of which escalated public health responses due to rising case counts.

What Is Chikungunya and Why Is It Dangerous?

Chikungunya typically begins suddenly with:

• High fever

• Intense joint pain

• Muscle aches

• Headache

• Skin rash

• Fatigue

While many patients recover within days, joint pain can persist for months or even years, especially in older adults and individuals with chronic illnesses. There is currently no antiviral treatment, making prevention essential.

Ixchiq: The First FDA-Approved Chikungunya Vaccine

What Makes Ixchiq Different?

Approved by the U.S. Food and Drug Administration (FDA) in November 2023, Ixchiq, developed by Valneva, became the first vaccine specifically designed to prevent chikungunya infection.

Key features include:

• Live-attenuated vaccine technology

• Single-dose administration

• Designed for long-lasting immune protection

Live-attenuated vaccines work by using a weakened version of the virus to stimulate a strong immune response, closely mimicking natural infection without causing illness in healthy individuals.

Who Was the Vaccine Initially Approved For?

At the time of approval, Ixchiq was authorized for:

• Adults 18 years and older

• Travelers to chikungunya-endemic regions

• Residents of high-risk areas

• Certain occupational groups, including healthcare and military personnel

However, due to its vaccine platform, it was not recommended for immunocompromised individuals or those with fragile health conditions unless benefits clearly outweighed risks.

Why Did the FDA and CDC Pause Use in Older Adults?

Safety Signals Trigger Review

On May 12, 2025, the FDA and Centers for Disease Control and Prevention (CDC) jointly recommended a temporary pause on administering Ixchiq to individuals aged 60 years and above.

This precaution followed reports of serious adverse events in older vaccine recipients.

Reported Adverse Events: What We Know So Far

According to regulatory safety data:

• 17 serious adverse events were reported globally

• Affected individuals were aged 62 to 89

• Two deaths were reported

• Events included neurological complications (such as encephalitis) and cardiac issues

Most cases involved individuals with existing medical conditions, which may have increased vulnerability to complications from a live vaccine.

International Response and EMA Review

The European Medicines Agency (EMA) launched its own safety investigation through the Pharmacovigilance Risk Assessment Committee (PRAC). As a precautionary measure, the EMA also suspended Ixchiq use in people aged 65 and older while data analysis continues.

Global coordination between regulatory bodies highlights the importance of post-marketing surveillance, particularly for newly approved vaccines.

What Older Travelers Should Do Now

If You Are 60 or Older and Planning Travel

Until safety reviews are complete:

• Delay Ixchiq vaccination

• Rely on strict mosquito-avoidance measures

• Consult a travel medicine specialist before departure

If You Were Recently Vaccinated

Seek immediate medical care if you experience:

• Chest pain or irregular heartbeat

• Confusion or altered consciousness

• Weakness or neurological symptoms

Always inform healthcare providers about recent vaccination history.

Guidance for Doctors and Healthcare Professionals

Medical professionals are advised to:

• Avoid prescribing Ixchiq to patients aged 60+

• Carefully evaluate cardiac and neurological history

• Report any suspected vaccine reactions through VAERS

Timely reporting plays a critical role in ensuring vaccine safety worldwide.

Preventing Chikungunya Without Vaccination

Mosquito Protection Remains Essential

For all age groups, especially older adults, prevention focuses on mosquito control:

• Wear long sleeves and full-length clothing

• Use EPA-approved repellents (DEET, picaridin, lemon eucalyptus oil)

• Sleep under mosquito nets

• Use window screens and air-conditioned rooms

• Remove standing water around living areas

Are Other Chikungunya Vaccines Coming?

Several alternative vaccines are in development, including:

• Virus-like particle (VLP) vaccines

• mRNA-based vaccines

• Protein subunit vaccines

These platforms may offer improved safety for older adults, but none are yet approved for public use.

What About Younger Adults?

The current advisory does not apply to adults aged 18–59. Ixchiq remains authorized for this group, with no new safety concerns identified. Continued monitoring is ongoing for all recipients.

Final Takeaway

The temporary pause in Ixchiq use among older adults reflects responsible vaccine safety monitoring, not a rejection of the vaccine itself. As regulatory agencies continue their evaluations, prevention through mosquito control remains the most reliable defense—particularly for vulnerable populations.

Staying informed, reporting side effects, and consulting healthcare professionals are key to navigating evolving public health guidance.