A novel chikungunya virus vaccine caused no serious adverse effects and was about as immunogenic as natural infection, authors of a phase I trial reported in the Lancet.
Eleven months after receiving the noninfectious viruslike particle (VLP) vaccine, trial participants had neutralizing antibody titers that resembled those seen in natural infection, said Dr. Lee-Jah Chang and associates at the National Institutes of Health in Bethesda, Md. (Lancet 2014 Aug. 15 [doi: 10.1016/S0140-6736(14)61185-5]).
Chikungunya virus infection is rarely fatal, but it causes fever and severe arthritis. The mosquito-born pathogen spread to the Americas in 2013, is now epidemic in the Caribbean, and has no approved vaccine or treatment.
To test a novel VLP vaccine candidate, researchers enrolled 25 healthy adults into a phase I, open-label, dose-escalation trial with doses of 10, 20, or 40 mcg administered at weeks 0, 4, and 20, the investigators reported. Participants were followed for 44 weeks after enrollment.
All groups had detectable neutralizing antibodies on ELISA (enzyme-linked immunosorbent assay) after the second dose, with geometric mean titers of the half-maximum inhibitory concentration of 2,688 in the 10-mcg group, 1,775 in the 20-mcg group, and 7,246 in the 40-mcg group. Antibody levels after the second dose substantially exceeded those measured after the first dose, with P values for differences ranging from .07 for the 10-mcg group to less than .0001 for the 40-mcg group, the investigators said. And titers did not significantly differ 4 weeks after the second and third doses, they added.
Participants reported no arthralgias or other serious adverse effects. Mild to moderate side effects occurred in four participants, and consisted of transient neutropenia (three cases) and transient increases in alanine aminotransferase (four cases), all of which resolved without clinical consequences, the investigators said.
"These clinical data represent an important step in vaccine development to combat this rapidly emerging pathogen," the researchers said. The next step is to test the vaccine in larger studies that include persons at risk of chikungunya virus infection, they added.
The trial was funded by the Intramural Research Program of the Vaccine Research Center, National Institute of Allergy and Infectious Diseases; and the National Institutes of Health. The authors declared no competing interests.