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Trial Shows Vaccine Induces Chikungunya Immune Response

Aedes aegypti mosquito

Aedes aegypti mosquito biting a human (U.S. Dept of Agriculture)

7 Aug. 2023. Initial findings from a large clinical trial testing a vaccine against the chikungunya virus show the vaccine generates protective antibodies in the vast majority of recipients. The results were released by biopharmaceutical company Bavarian Nordic A/S in Copenhagen, Denmark, developer of the candidate vaccine code-named CHIKV VLP, and are not yet peer-reviewed.

Chikungunya is a viral disease spread by mosquitoes, causing fever and severe joint pain, and often joint swelling, headache, nausea, fatigue, and rash. Symptoms in most people last a few days, but for others can continue for weeks and months, and become debilitating. Because chikungunya symptoms are similar to Zika and dengue, misdiagnoses are common, and the condition is often underreported.  The disease was first diagnosed in Africa and Asia, where Aedes aegypti and Aedes albopictus mosquitoes reside, but has since spread to the Americas, including the U.S. As yet, there are no approved treatments nor vaccines for chikungunya.

Bavarian Nordic is an established vaccine developer and manufacturer with several products approved and on the market for encephalitis, smallpox and monkeypox, rabies, cholera, and typhoid. Of its vaccines in development, chikungunya and SARS-CoV-2 are in late-stage clinical trials. The company’s technology is derived from modified vaccinia Ankara, a weakened and benign form of smallpox that does not replicate in recipients. Bavarian Nordic says the technology produces vaccines that generate both antibodies as well as cellular immune responses. The company’s CHIKV VLP candidate vaccine delivers virus-like particles on an aluminum hydroxide adjuvant designed to induce immune responses in recipients.

Protective levels of neutralizing antibodies

Bavarian Northern is testing CHIKV VLP in two late-stage clinical trials among healthy participants, one study with people age 65 and over and the other with younger adults and adolescents, age 12 to 64. In the latter trial with results reported yesterday, the study team enrolled 3,254 participants across the U.S. Participants were randomly assigned to receive a single dose of CHIKV VLP vaccine or a placebo, with individuals first tracked for 22 days, then six months. Researchers looked for anti-chikungunya antibody concentrations in blood samples after those intervals, as well as adverse effects.

Findings reported by Bavarian Northern show CHIKV VLP induces protective levels of neutralizing antibodies against chikungunya viruses in 98 percent of recipients after 22 days, with the percentage of participants with protective levels of antibodies dropping off somewhat to 86 percent after six months. The company says the vaccine is well tolerated among adolescents and adults up to age 64 with adverse effects rated mild or moderate, but no efficacy nor adverse effects results from the placebo group are reported.

In the second late-stage clinical trial, among 413 healthy adults age 65 and over and reported in June 2023, Bavarian Northern says 82 percent reported protective concentrations of antibodies after 15 days, with that percentage growing to 87 percent by 22 days. The company says the vaccine was well tolerated among recipients with rates of adverse effects similar for vaccine and placebo recipients. Six-month follow-up data, says the company, are still being collected.

Paul Chaplin, president and CEO of Bavarian Nordic, says in a company statement, “Our focus remains to finalize the studies and prepare for regulatory submissions next year.” Chaplin adds, “Chikungunya can often result in a severe and incapacitating disease that affects large parts of the world, and with international travel on the rise again, our CHIKV vaccine offers a significant opportunity to address this large unmet medical need.”

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