On Nov. 9, 2023, the U.S. Food and Drug Administration (FDA) approved Valneva’s Ixchiq, the first chikungunya vaccine. Ixchiq is approved for individuals 18 years of age and older who are at increased risk of exposure to chikungunya virus.

The chikungunya virus is primarily transmitted to people through the bite of an infected mosquito. Chikungunya is an emerging global health threat with at least 5 million cases of chikungunya virus infection reported during the past 15 years. The highest risk of infection is in tropical and subtropical regions of Africa, Southeast Asia, and parts of the Americas where chikungunya virus-carrying mosquitos are endemic. However, chikungunya virus has spread to new geographical areas causing a rise in global prevalence of the disease.

The most common symptoms of chikungunya include fever and joint pain. Other symptoms may include a rash, headache, and muscle pain. Some individuals may experience debilitating joint pain that persists for months or even years. Treatment includes rest, fluids, and over-the-counter medications for pain and fever.

Ixchiq is administered as a single dose by injection into the muscle. It contains a live, weakened version of the chikungunya virus and may cause symptoms in the vaccine recipient similar to those experienced by people who have chikungunya disease.

The safety of Ixchiq was evaluated in two clinical studies conducted in North America in which about 3,500 participants 18 years of age and older received a dose of the vaccine with one study including about 1,000 participants who received a placebo. The most commonly reported side effects by vaccine recipients were headache, fatigue, muscle pain, joint pain, fever, nausea and tenderness at the injection site.

The effectiveness of Ixchiq is based on immune response data from a clinical study conducted in the United States in individuals 18 years of age and older. In this study, the immune response of 266 participants who received the vaccine was compared to the immune response of 96 participants who received placebo. The level of antibody evaluated in study participants was based on a level shown to be protective in non-human primates that had received blood from people who had been vaccinated. Almost all vaccine study participants achieved this antibody level.

Ixchiq was approved using the Accelerated Approval pathway. Accelerated approval allows the FDA to approve certain products for serious or life-threatening conditions based on evidence of a product’s effectiveness that is reasonably likely to predict clinical benefit. In the FDA’s evaluation of Ixchiq for accelerated approval, evidence of effectiveness is based on immune response data in clinical trial participants. As a condition for approval for Ixchiq, the FDA is requiring confirmatory clinical studies to be conducted to verify clinical benefit.