MVA-BN-RSV Vaccine Effective in Lowering Viral Load, Reducing RSV Infections

According to a study published in The Journal of Infectious Diseases, lower viral load, lower symptom scores, fewer infections, and induced humoral and cellular responses were reported after patients received the MVA-BN-RSV vaccine for respiratory syncytial virus (RSV).

RSV, which is a recurring and common infectious disease, most often strikes young infants who are high risk. An estimated 120,000 children aged less than 5 years die from RSV around the world. Older adults are also at a higher risk of contracting RSV. A novel vaccine, MVA-BN-RSV, aims for immunogenicity by inducing humoral and cellular responses to RSV proteins. This study aimed to evaluate the safety and immunogenicity of the MVA-BN-RSV vaccine through a human challenge trial.

The phase 2a, randomized, double-blind, placebo-controlled trial evaluated the efficacy of the MVA-BN-RSV vaccine against the Memphis 37b strain of RSV. The study took place in London, United Kingdom by hVIVO Services Limited at the Queen Mary BioEnterprises Innovation Centre from January to November 2021. All participants were aged 18 to 50 years and were expected to be susceptible to RSV based on neutralizing antibody titers.

All participants were randomized into placebo and MVA-BN-RSV groups. All participants collected data on adverse effects, and blood was collected to assess antibody measurements. Participants entered quarantine 2 days prior to injection of the challenge virus, which came 4 weeks after vaccination. All participants were observed for 12 days after injection and then followed after discharge. Incidence of infection was calculated as the proportion of participants infected from Day 2 until the end of quarantine.

There were 61 participants who were included in this analysis, with baseline characteristics similar between the placebo and MVA-BN-RSV groups (median age 25 years and 26.5 years; female sex 45.9% and 36.1%; white race 89.2% and 91.7%, respectively).

The area under curve (AUC) of RSV Memphis 37b was lower in the MVA-BN-RSV group (median, 0.00; IQR 0.00-53.44) than in the placebo group (median, 49.05; IQR 0.00-999.94). The viral load AUC by quantitative virus culture was found to be lower in the MVA-BN-RSV group, with the differences mostly occurring in Days 3 to 7. Less disease acuity was also found in the MVA-BN-RSV group when using peak viral load measures.

Vaccine efficacy was found to range from a low of 9.6% for infection confirmed through a laboratory measure to a peak of 58.7% for infection confirmed by a laboratory measure and the presence of a symptom of RSV when using priori definitions. When an infection was defined using viral load the efficacy ranged from 51.8% to 79.3%. The vaccine had 88.5% efficacy when the infection was defined by virus culture results.

Both immunglobin A and immunoglobin G saw the largest increases in geometric mean titers (GMT) from baseline to 2 weeks after vaccination with neither increasing in response to challenge. The placebo group had smaller increases in response, which peaked at 28 days. The most common adverse effects reported were injections site pain.

The researchers concluded that the MVA-BN-RSV vaccine was able to lower viral load AUC after challenge with the RSV Memphis 37b strain compared with the placebo. Vaccine efficacy between 79.3% and 88.5% was found when measuring by viral load.

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