The US Food and Drug Administration (FDA) announced on Thursday the approval of Ixchiq, the first vaccine for the prevention of chikungunya virus disease in adults at increased risk of exposure.
Chikungunya is a mosquito-borne viral disease whose name means “that which bends up” in the Makonde language of Tanzania and Mozambique. The disease is characterized by high fever and severe joint pain which can be debilitating and even fatal in newborns.
The virus is transmitted to people by two species of mosquitoes – Aedes aegypti and Aedes albopictus. These mosquitoes bite during the daytime and are found throughout much of the Americas, including parts of the United States.
Chikungunya outbreaks have occurred since the 1950s in Africa, Asia, Europe, and the Indian and Pacific Oceans. However, the disease was not detected in the Americas until late 2013 when the first local transmission was reported on islands in the Caribbean.
Since then, more than 3 million suspected cases have been recorded in 45 countries and territories in the Americas. Several US states, including Florida, Texas, and Puerto Rico, have reported local transmission.
According to the World Health Organization (WHO), chikungunya is considered an emerging threat to global health exacerbated by climate change. At least 5 million cases have been reported globally in the past 15 years.
Symptoms and Treatment
The most common symptoms of chikungunya virus infection are fever and joint pain. Other symptoms may include headache, muscle pain, joint swelling, and rash.
Joint pain is often debilitating and can persist for weeks to years. Older adults and those with underlying medical conditions are at risk of more severe disease outcomes.
There are no specific treatments for the disease. Care is focused on relieving symptoms with rest, fluids, and medications for fever and pain.
Infants infected around the time of birth are at risk of severe and life-threatening complications. Newborn mortality associated with chikungunya ranges from 5% to 48%, according to the European Centre for Disease Prevention and Control.
In the absence of targeted therapies, vaccination represents the best option for controlling chikungunya and preventing disease, especially in high-risk regions.
Ixchiq is a live, attenuated vaccine developed by Valneva Austria GmbH. The vaccine contains a weakened form of the chikungunya virus that provokes protective immunity without causing illness.
The vaccine was granted fast track and breakthrough therapy designation by the FDA due to the lack of treatment options and the potential to address an unmet medical need.
Efficacy and Safety Data
The FDA based its approval on results from two randomized, placebo-controlled Phase 3 trials involving over 3,500 adults aged 18 years and older. The trials were conducted at sites in the United States and internationally.
In both trials, a single dose of Ixchiq was highly efficacious in preventing chikungunya disease. Vaccine efficacy ranged from 79% to 93% starting 14 days after vaccination. Protection lasted for at least 1 year.
The most common side effects were headache, muscle pain, joint pain, injection site tenderness, fatigue, and fever. Most reactions were mild to moderate in severity.
Severe chikungunya-like reactions requiring medical care occurred in less than 2% of vaccine recipients. Only two hospitalizations were reported out of nearly 3,500 vaccinated individuals.
Warnings and Precautions
As Ixchiq contains live, weakened virus, vaccination may result in chikungunya-like symptoms. Vaccinees should avoid mosquito exposure for up to 28 days to prevent transmission.
The vaccine virus can persist in blood for several weeks and has the potential to pass from mother to baby during pregnancy. The risks and benefits of vaccination should be assessed for pregnant women based on risk of exposure.
Healthcare providers should advise receipients about possible side effects and ensure monitoring of vaccine complications. Use of Ixchiq should be avoided in persons with severe immunodeficiency.
Approval and Recommendations
Ixchiq is approved for use in adults aged 18 years and older who are at increased risk of chikungunya virus infection. At-risk groups include:
- Travelers going to areas with chikungunya outbreaks
- Laboratory workers handling the virus
- Military personnel deployed to endemic regions
The vaccine is administered as a single 0.5 mL dose by subcutaneous injection. The FDA has requested that the manufacturer conduct a post-approval observational study to evaluate safety risks in a real-world setting.
Public health officials recommend vaccination for people traveling to or living in high-risk areas, especially if outbreaks are occurring. Routine vaccination is not advised for lower risk populations at this time.
Peter Marks, Director of the FDA’s Center for Biologics Evaluation and Research, commented, “Infection with chikungunya virus can lead to severe disease, and today’s approval addresses a significant public health need. This vaccine provides an important tool for reducing the disease burden from this virus.”
The approval of Ixchiq represents a major advance in controlling the emerging threat posed by chikungunya virus in the face of climate change and rising global temperatures. Ongoing research efforts are focused on assessing vaccine effectiveness against new viral variants and potential expanded use in broader populations.