What Do We Know About The New Chikungunya Vaccine So Far?

The world of travel health has just gotten a little more exciting with the recent approval in the UK of IXCHIQ®, the first-ever vaccine designed to protect adults against the debilitating Chikungunya virus. This ground-breaking development, marks a crucial step forward in safeguarding travellers and individuals in endemic regions.

What is Chikungunya?

Chikungunya, a mosquito-borne viral disease, has long been a significant concern for travellers venturing into tropical and subtropical areas of Africa, Asia, and the Americas. The virus is primarily transmitted through the bites of infected Aedes aegypti and Aedes albopictus mosquitoes, which are known to bite predominantly during the daytime and around dusk/dawn.

Characterised by a sudden onset of fever and severe joint pain – often so intense it’s described as “that which bends up” in the Kimakonde language of southern Tanzania from which the name originates – Chikungunya can also cause muscle pain, headache, nausea, fatigue, and a maculopapular rash. The joint pain is often symmetrical, affecting areas like the hands, wrists, ankles, and feet, and can be accompanied by joint swelling and stiffness.

While typically not fatal, the long-term effects of Chikungunya can be significant. A substantial proportion of individuals develop post-chikungunya chronic arthralgia, where the debilitating joint pain persists for months or even years, severely impacting their quality of life, ability to work, and participation in daily activities.

Diagnosis and Management of Chikungunya

Chikungunya can have very similar symptoms to Dengue and Zika virus, which can often make diagnosis challenging. Diagnosis of Chikungunya typically involves blood tests to detect the presence of the virus or specific antibodies produced by the immune system in response to the infection. Currently, there is no specific antiviral treatment for Chikungunya. Management focuses on supportive care to relieve symptoms, such as rest, adequate fluid intake, and the use of painkillers like paracetamol.

Historically, chikungunya has been limited to tropical and subtropical regions, but climate change and increased international travel are widening its geographical footprint. Notable outbreaks have occurred in parts of Africa, Asia, Europe, and the Americas.

What We Know About the New Chikungunya Vaccine: IXCHIQ®

Until recently, travellers and residents in endemic areas had no vaccine option for chikungunya. Prevention strategies primarily focused on avoiding mosquito bites through insect repellent, protective clothing, and mosquito nets. While these measures remain important, the approval of IXCHIQ® offers a proactive layer of protection for at-risk individuals.

IXCHIQ® is a single-dose, live-attenuated vaccine developed by Valneva. Unlike inactivated vaccines, live-attenuated vaccines use a weakened form of the virus to stimulate a strong and long-lasting immune response. Because it’s a single-dose vaccine, it offers a significant advantage for travellers who may have limited time before their trip or prefer a simpler vaccination schedule.

Why the Chikungunya Vaccine is a Game-Changer

IXCHIQ® was first approved by the FDA for use in the USA in November 2023, marking an earlier milestone in the fight against this virus. In a significant step for endemic regions, the Brazilian Health Regulatory Agency (ANVISA) recently authorised IXCHIQ® for use in people ages 18 and older, marking the first approval of a Chikungunya vaccine in a country heavily affected by the disease. This approval in Brazil, which has recorded over a million cases between 2019 and 2024, paves the way for further clinical trials in the country to assess real-world effectiveness and is seen as a crucial step in expanding access to this vital preventative measure in endemic areas and for travellers.

Now, with its approval by the Medicines and Healthcare products Regulatory Agency (MHRA) in February 2025, IXCHIQ® is the first licensed vaccine to protect adults aged 18 and older against chikungunya virus in the UK.

Use of the Chikungunya Vaccine in the UK

It’s important to note that while IXCHIQ® has received regulatory approval in the UK, the UK’s Joint Committee on Vaccination and Immunisation (JCVI), whose recommendations are published in the Green Book, have not yet released their specific guidance on the use of this vaccine.

This means that while the vaccine is authorised for use in adults, detailed recommendations regarding who should receive it, under what circumstances, and its place within the broader travel health landscape are still pending official publication in the Green Book. Travel health practitioners should therefore ensure they stay informed through official channels and exercise careful clinical judgement when advising patients about the IXCHIQ® vaccine.

While the UK’s JCVI is yet to issue specific guidance, the vaccine is likely to be particularly beneficial for:

• Travellers to high-risk areas: Those visiting tropical and subtropical regions where Chikungunya is endemic or where outbreaks occur, particularly those who are travelling for prolonged periods of time.
• Laboratory personnel handling the virus: Individuals working with live Chikungunya virus are at higher risk of exposure.
• Aid workers, volunteers and military personnel: Those working in affected areas may have increased exposure risks.

The vaccine is not currently licensed for use in children, pregnant women, and where it is a live vaccine it is contraindicated for immunocompromised individuals. Further details can be found in the Summary of Product Characteristics (SmPC).

How Effective is IXCHIQ®?

Clinical trials have shown IXCHIQ® to be highly effective and have provided valuable data on the safety and efficacy of the vaccine. Key findings include:

• Efficacy: Studies have shown that a single dose of IXCHIQ® is effective in eliciting an immune response against the Chikungunya virus. According to the SmPC, 99% of participants in clinical trials developed protective levels of antibodies within one month of vaccination. While studies on the duration of protection are ongoing, early findings suggest a strong and lasting immune response. Follow-up data revealed that 97% of vaccinated individuals maintained these protective antibody levels two years post-vaccination.
• Safety: The most commonly reported side effects in clinical trials were generally mild and short-lived, including headache, fatigue, muscle pain, joint pain, fever, and nausea. IXCHIQ® has been found to have caused severe or prolonged chikungunya-like adverse reactions in some individuals. More serious adverse events were rare. The US Centers for Disease Control and Prevention (CDC) are currently investigating five hospitalisations for cardiac or neurologic events following vaccination in those over the age of 65 years, although investigations are still ongoing whether this is is a causal relationship or coincidental.

As IXCHIQ® is a newly licensed vaccine, real-world data collection through post-marketing surveillance will continue to refine understanding of its long-term effectiveness and safety profile.

Travel Health Considerations

Even when IXCHIQ® becomes more widely available, standard mosquito bite prevention strategies remain crucial. These include using DEET-based repellents, sleeping under mosquito nets, wearing long-sleeved clothing, and staying in accommodations with effective mosquito control measures. The vaccine adds a significant layer of protection but doesn’t replace these essential practices.

In Summary

The Chikungunya vaccine, IXCHIQ® represents a major advancement in preventing infection in adults in the UK and worldwide. Its single-dose nature, demonstrated efficacy, and acceptable safety profile make it a promising tool for protecting travellers and, potentially in the future, individuals in endemic regions. However, in the UK context, we eagerly await specific guidance from the JCVI and the Green Book to understand its precise role in the broader travel health landscape.

05/05/2025 Update: Since the original publication of this blog post, the MHRA has approved a second Chikungunya vaccine: Vimkunya® on the 1st May 2025. Developed by Bavarian Nordic, it is authorised for individuals aged 12 and above. Clinical trials showed strong effectiveness, with up to 98% of those age 12-64 and 87% of those 65 years + developing neutralising antibodies within 21 days of a single dose. As an inactivated, recombinant protein vaccine, Vimkunya® offers an alternative for those who cannot receive live vaccines.

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