Reisinger EC, et al. - Researchers investigated the safety, tolerability, and immunogenicity of a live-attenuated, measles-vectored chikungunya vaccine (MV-CHIK). In this double-blind, randomized, placebo-controlled and active-controlled phase 2 trial, MV-CHIK displayed excellent safety and tolerability and good immunogenicity. The findings were evident irrespective of pre-existing immunity against the vector. This highlights the potential utility of MV-CHIK for the prevention of chikungunya fever, an emerging global disease.

Methods

• Researchers recruited healthy volunteers aged 18–55 years at four study sites in Austria and Germany in this double-blind, randomized, placebo-controlled and active-controlled phase 2 trial.
• They randomly assigned the participants to receive intramuscular injections with MV-CHIK (5 × 10⁴ or 5 × 10 ⁵ 50% tissue culture infectious dose), control vaccine, or measles prime and MV-CHIK, in two different administration regimens.
• Three-digit randomization codes in envelopes provided by a data management service were used to perform randomization.
• Treatment assignment was not revealed to the participants and investigators; this was maintained by use of sterile saline as a placebo injection.
• Immunogenicity, defined as the presence of neutralizing antibodies against chikungunya virus, at day 56, which is 28 days after one or two immunizations, was assessed as the primary endpoint.
• All participants who completed the study without major protocol deviations (per-protocol population) and all randomized participants who received at least one study treatment (modified intention-to-treat population) were assessed for the primary endpoint.
• All participants who received at least one study treatment were included in the safety analysis.

Results

• Two hundred sixty-three participants were randomly assigned to receive control vaccine (n=34), MV-CHIK (n=195), or measles prime and MV-CHIK (n=34) between August 17, 2016 and May 31, 2017; the per-protocol population consisted of 247 participants.
• In all MV-CHIK treatment groups, researchers detected neutralizing antibodies against chikungunya virus after one or two immunizations, with geometric mean titres ranging from 12.87 (95% CI 8.75–18.93) to 174.80 (119.10–256.50) and seroconversion rates ranging from 50.0% to 95.9%, depending on the dose and administration schedule.
• The groups were similar regarding adverse event rates; solicited adverse events were reported in 168 (73%) of 229 participants assigned to MV-CHIK and 24 (71%) of 34 assigned to control vaccine (p=0.84) and unsolicited adverse events in 116 (51%) participants assigned to MV-CHIK and 17 (50%) assigned to control vaccine (p=1.00).
• They identified no vaccine related serious adverse events.