Experimental chikungunya vaccine in clinical trial
An experimental chikungunya vaccine prompted an immune response in all 25 volunteers in an early-stage clinical trial. Researchers believe an effective vaccine could prevent future outbreaks of the disease.
According to the latest data from the Pan American Health Organization, so far this year there have been chikungunya outbreaks in approximately 50 countries in the Americas and the Caribbean, with officially 748,403 suspected cases, 11,545 confirmed cases and 141 deaths.
There are currently no vaccines or specific treatments for chikungunya. In 2010, scientists at the National Institute of Health's H's National Institute of Allergy and Infectious Diseases (NIAID) in the United States and colleagues tested an experimental chikungunya vaccine in non-human primates. They found that all the vaccinated animals were protected from infection by the virus.
Whereas traditional vaccines are typically made from either killed viruses or weakened live viruses, the experimental vaccine is a virus-like particle (VLP) vaccine. These vaccines contain outer shell proteins of the virus but lack components the virus needs to replicate. Because they contain no viral genetic material, VLPs can't become active viruses and don't need to be produced under high-level biocontainment conditions.
The researchers, led by NIAID's Dr Julie E. Ledgerwood, enrolled 25 healthy adults in an early-stage clinical trial. The volunteers received three injections over 20 weeks at one of three different vaccine dosages (10, 20, or 40 micrograms). Antibody production (a measure of immune system response) was measured at multiple time points following each injection. The trial was completed by all but two volunteers, who left the study for personal reasons unrelated to the study. The study appeared online in August in the Lancet.
Chikungunya-neutralising antibodies were detected in all volunteers following the second injection, with a significant boost of antibodies following the third injection. The antibodies persisted in all volunteers, even those who received the lowest dosage, for at least 11 months after the final vaccination.
"The candidate vaccine prompted a robust immunological response in recipients and was very well tolerated," Ledgerwood said. "Notably, the levels of neutralising antibody produced in response to the experimental vaccine were comparable to those seen in two patients who had recovered from a chikungunya virus infection acquired elsewhere."
The researchers plan to continue working on the vaccine.