CHIKUNGUNYA VACCINE WARNING FOR OLDER ADULTS: FDA, CDC ISSUE ADVISORY
Medically Reviewed by Dr. Sony Sherpa (MBBS)
Chikungunya is a viral infection spread mainly by the Aedes aegypti and Aedes albopictus mosquitoes, which also transmit dengue and Zika viruses. First identified in Tanzania in the 1950s, chikungunya has since caused multiple outbreaks across Africa, Asia, Europe, and the Americas.
From January to the start of June 2025, over 220,000 chikungunya virus disease (CHIKVD) cases and 80 related fatalities were reported across 14 countries, with the majority occurring in the Americas, particularly Brazil (141,436 cases), followed by Argentina, Bolivia, and Peru. While there were no reported cases in mainland Europe, significant outbreaks were recorded in the French outermost regions of Réunion (over 51,000 cases) and Mayotte (560 cases), both of which were under elevated epidemic response levels as of the time of writing.
The virus is known for causing sudden-onset fever, severe joint pain, headache, muscle pain, rash, and fatigue. In most individuals, symptoms resolve within a week, but joint pain can persist for months, particularly in older adults and those with pre-existing conditions. There is no specific antiviral treatment, making prevention - through mosquito control and vaccination - the cornerstone of public health response in endemic and outbreak-prone regions.
Aiming to protect vulnerable populations from this debilitating disease, the U.S. Food and Drug Administration (FDA) approved the chikungunya vaccine, Ixchiq, in November 2023. Developed by Valneva, the vaccine promised a much-needed preventive measure for a disease with a growing geographic spread due to climate change and global travel.
However, the vaccine’s rollout has recently encountered a significant roadblock. On May 12, 2025, the FDA and the Centers for Disease Control and Prevention (CDC) issued a joint announcement recommending to pause the use of Ixchiq in individuals aged 60 and older. This advisory follows a series of serious adverse events reported in older recipients of the vaccine. The CDC emphasized that the recommendation is precautionary, issued while additional safety reviews are conducted.
The announcement has prompted global concern, particularly among healthcare providers and travelers in the affected age group. As regulators conduct ongoing safety assessments, the pause highlights the importance of continuous pharmacovigilance, especially when deploying new vaccines in older populations.
What is The Ixchiq Vaccine?
Ixchiq is the first live-attenuated vaccine developed specifically to prevent chikungunya virus infection. It was designed to offer single-dose, long-term protection against the virus - a major advancement considering the global burden and increasing spread of this mosquito-borne disease.
The vaccine received FDA approval in November 2023 for use in adults over 18 years, particularly those traveling to or residing in regions where chikungunya virus transmission is ongoing. This decision was based on clinical trials demonstrating a strong immune response in recipients and a safety profile that was generally well-tolerated in healthy adults. At the time of approval, Ixchiq was hailed as a breakthrough, especially for at-risk populations and public health programs in endemic areas.
Ixchiq works through a live-attenuated virus platform, which means that it contains a weakened form of the chikungunya virus that stimulates the immune system to identify and fight the virus without causing disease in healthy individuals. Unlike inactivated or subunit vaccines, live-attenuated vaccines tend to provoke a robust and durable immune response, often after just one dose, because they closely mimic natural infection.
As mentioned above, the target demographics for Ixchiq included healthy adults aged 18 and older. Besides travelers to endemic regions and individuals living in high-risk areas, this includes military personnel and healthcare workers. However, due to its live-attenuated nature, the vaccine was not recommended for immunocompromised individuals or those with certain underlying conditions, including older adults with frail health, unless the benefits outweighed the potential risks.
With chikungunya outbreaks increasingly reported across the Americas, Africa, Asia, and parts of Europe, the approval of Ixchiq marked a significant milestone in preventive healthcare. Yet, as with all live vaccines, careful post-market surveillance is critical to detecting rare or delayed adverse events, particularly in older populations who may have underlying vulnerabilities.
Reason for the "Time Out": Emerging Safety Concerns and Reported Adverse Events
The May 2025 joint decision by the FDA and the CDC followed the identification of serious adverse events (SAEs) in older adults who had recently received the vaccine.
Summary of Reported Adverse Events
As of the advisory, a total of 17 serious adverse events were reported worldwide among vaccine recipients aged 62 to 89 years, including two deaths. The FDA notes that these reports were submitted through the Vaccine Adverse Event Reporting System (VAERS) and international channels. The types of adverse events included neurologic conditions (such as encephalitis) and cardiac issues, raising concerns about potential risks in the elderly population, particularly those with pre-existing medical conditions.
EMA's Safety Review
Simultaneously, the European Medicines Agency (EMA) announced its own safety review of Ixchiq, initiated by the Pharmacovigilance Risk Assessment Committee (PRAC). EMA noted that while the total number of cases is small, the serious nature of the events, including neurologic and cardiac complications in patients aged 65 years and above, justified a formal risk evaluation.
Most of the affected individuals were found to have underlying medical conditions that may have increased their vulnerability to complications from a live-attenuated vaccine.
Ongoing Safety Assessments
The FDA and CDC continue to review data from the VAERS, international surveillance, and manufacturer-submitted reports. Investigations are focused on understanding the possible link between the live-attenuated virus in Ixchiq and the neurological and cardiac events reported, especially among individuals with underlying health issues.
European Response
According to a May 2025 report by Reuters, the EMA's review follows multiple reports of serious side effects, including in people over 65. These efforts mirror the FDA's cautionary stance and signal a global re-evaluation of the vaccine’s risk-benefit balance for older populations. In the meantime, the agency has also temporarily suspended the use of Ixchiq in individuals aged 65-plus.
Implications for Travelers and Healthcare Providers
For Travelers Aged 60 and Above
Individuals 60 years and older who are planning to travel to chikungunya-endemic regions are advised to postpone receiving the Ixchiq vaccine until further safety data becomes available. The FDA and CDC stress the importance of using alternative preventive strategies, such as mosquito bite avoidance through repellents, protective clothing, and bed nets.
For Those Recently Vaccinated
Individuals in the 60+ age group who have recently received the Ixchiq vaccine should be vigilant for unusual symptoms, especially those involving the heart or nervous system, such as chest pain, palpitations, confusion, or weakness. These individuals should seek immediate medical attention and inform their provider of their vaccination history.
Guidance for Healthcare Providers
Clinicians are advised to defer administration of the Ixchiq vaccine to patients aged 60 or older, unless a compelling benefit outweighs the risk. Providers should review patient medical histories thoroughly, particularly for cardiovascular and neurological conditions, before considering vaccination in borderline cases.
Importance of Adverse Event Reporting
Healthcare professionals should report any suspected vaccine-related adverse events using the VAERS to support national and international safety monitoring. Prompt reporting ensures real-time data collection for ongoing pharmacovigilance and regulatory decision-making.
Alternative Preventive Measures
Mosquito Bite Prevention Strategies
For all travelers, especially those over 60, mosquito avoidance remains the most effective preventive measure against the chikungunya virus. Key strategies include:
- Wearing long-sleeved clothing and pants, particularly during daylight hours when Aedes mosquitoes are most active.
- Applying EPA-registered insect repellents like DEET, picaridin, or oil of lemon eucalyptus.
- Using mosquito nets and window screens, especially in regions without air conditioning.
- Eliminating standing water around homes to reduce mosquito breeding sites.
These precautions are vital for all age groups but especially critical now for older adults unable to receive the Ixchiq vaccine during the ongoing review.
Other Vaccine Candidates Under Development
Several alternative chikungunya vaccine candidates are currently under investigation in clinical trials. These include:
- Virus-like particle (VLP) vaccines, which are non-replicating and may present a safer profile for older adults.
- mRNA-based vaccines and protein subunit vaccines, offering newer platforms with potentially fewer risks for individuals with comorbidities.
However, none are yet approved for public use, and their availability is still pending safety and efficacy evaluations. The pause in Ixchiq use may increase urgency in evaluating these next-generation candidates.
What This Means for Other Age Groups
The current FDA and CDC advisory applies only to individuals aged 60 and older. The Ixchiq vaccine remains authorized for use in adults 18 to 59 years of age, with no changes in guidance for this group. No elevated risk signals have been identified in this demographic, and younger travelers may still receive the vaccine if traveling to high-risk areas.
However, continued vigilance is encouraged across all age groups, and any unusual symptoms following vaccination should be reported to healthcare providers and VAERS.
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