Trial Finds Lower Viral Load, Symptom Scores With MVA-BN-RSV Vaccine

A novel respiratory syncytial virus (RSV) vaccine led to lower viral load and symptom scores and fewer confirmed infections in a human challenge trial, according to results published online ahead of print in The Journal of Infectious Diseases.

“MVA-BN-RSV is a novel vaccine aimed at broad immunogenicity,” researchers explained, “inducing both humoral and cellular responses to multiple RSV proteins.”

The double-blind phase 2a trial included healthy adults between ages 18 and 50 who were randomized to receive either MVA-BN-RSV or placebo. Among participants, 31 who received the vaccine and 32 who received placebo were challenged 4 weeks later with RSV-A Memphis 37b.

Viral load areas under the curve from nasal washes were a median 0.00 with the vaccine and 49.05 with placebo, according to the study. Symptom scores were a median 2.50 with the vaccine and 27.00 with placebo.

The efficacy of the vaccine against symptomatic, laboratory-confirmed, or culture-confirmed RSV infection was between 79.3% and 88.5%.

Researchers also reported humoral and cellular response induced by the vaccine. Serum immunoglobulin A and G titers increased approximately 4-fold, and interferon-γ–producing cells increased 4- to 6-fold in response to stimulation with encoded RSV internal antigens.

“Humoral and cellular responses support broad immunogenicity of the vaccine. Injection site pain was the most common adverse event,” the authors wrote. “Phase 3 evaluation of MVA-BN-RSV to determine clinical efficacy in an older adult population has commenced (NCT05238025).”

Reference: 
Jordan E, Kabir G, Schultz S, et al. Reduced respiratory syncytial virus load, symptoms, and infections: a human challenge trial of MVA-BN-RSV vaccine. J Infect Dis. Published online April 20, 2023. doi:10.1093/infdis/jiad108