• Grace L Chen, Emily E Coates, Sarah H Plummer, Cristina A Carter, Nina Berkowitz, Michelle Conan-Cibotti, Josephine H Cox, Allison Beck, Mark O'Callahan, Charla Andrews, Ingelise J Gordon, Brenda Larkin, Rebecca Lampley, Florence Kaltovich, Jason Gall, Kevin Carlton, Jason Mendy, Doug Haney, Jeanine May, Amy Bray, Robert T Bailer, Kimberly A Dowd, Brittanie Brockett, David Gordon, Richard A Koup, Richard Schwartz, John R Mascola, Barney S Graham, Theodore C Pierson, Yeycy Donastorg, Nicolas Rosario, Jean William Pape, Bruno Hoen, André Cabié, Clemente Diaz, Julie E Ledgerwood, and VRC 704 Study Team.
• Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland.
• JAMA. 2020 Apr 14; 323 (14): 1369-1377.

ImportanceChikungunya virus (CHIKV) is a mosquito-borne Alphavirus prevalent worldwide. There are currently no licensed vaccines or therapies.ObjectiveTo evaluate the safety and tolerability of an investigational CHIKV virus-like particle (VLP) vaccine in endemic regions.Design, Setting, And ParticipantsThis was a randomized, placebo-controlled, double-blind, phase 2 clinical trial to assess the vaccine VRC-CHKVLP059-00-VP (CHIKV VLP). The trial was conducted at 6 outpatient clinical research sites located in Haiti, Dominican Republic, Martinique, Guadeloupe, and Puerto Rico. A total of 400 healthy adults aged 18 through 60 years were enrolled after meeting eligibility criteria. The first study enrollment occurred on November 18, 2015; the final study visit, March 6, 2018.InterventionsParticipants were randomized 1:1 to receive 2 intramuscular injections 28 days apart (20 µg, n = 201) or placebo (n = 199) and were followed up for 72 weeks.Main Outcomes And MeasuresThe primary outcome was the safety (laboratory parameters, adverse events, and CHIKV infection) and tolerability (local and systemic reactogenicity) of the vaccine, and the secondary outcome was immune response by neutralization assay 4 weeks after second vaccination.ResultsOf the 400 randomized participants (mean age, 35 years; 199 [50%] women), 393 (98%) completed the primary safety analysis. All injections were well tolerated. Of the 16 serious adverse events unrelated to the study drugs, 4 (25%) occurred among 4 patients in the vaccine group and 12 (75%) occurred among 11 patients in the placebo group. Of the 16 mild to moderate unsolicited adverse events that were potentially related to the drug, 12 (75%) occurred among 8 patients in the vaccine group and 4 (25%) occurred among 3 patients in the placebo group. All potentially related adverse events resolved without clinical sequelae. At baseline, there was no significant difference between the effective concentration (EC50)-which is the dilution of sera that inhibits 50% infection in viral neutralization assay-geometric mean titers (GMTs) of neutralizing antibodies of the vaccine group (46; 95% CI, 34-63) and the placebo group (43; 95% CI, 32-57). Eight weeks following the first administration, the EC50 GMT in the vaccine group was 2005 (95% CI, 1680-2392) vs 43 (95% CI, 32-58; P < .001) in the placebo group. Durability of the immune response was demonstrated through 72 weeks after vaccination.Conclusions And RelevanceAmong healthy adults in a chikungunya endemic population, a virus-like particle vaccine compared with placebo demonstrated safety and tolerability. Phase 3 trials are needed to assess clinical efficacy.Trial RegistrationClinicalTrials.gov Identifier: NCT02562482.

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