An Expert Review and Strategic Analysis of RSV/Flu-01E: An Influenza-Vectored Intranasal Vaccine Candidate for Respiratory Syncytial Virus

Executive Summary

This report provides a comprehensive analysis of RSV/Flu-01E, an investigational intranasal vaccine for the prevention of Respiratory Syncytial Virus (RSV) infection, developed by the Smorodintsev Research Institute of Influenza in St. Petersburg, Russia. The candidate utilizes a novel influenza virus vector to express the RSV fusion (F) protein, a scientifically validated antigenic target. This platform offers a compelling theoretical advantage over existing intramuscular vaccines by aiming to induce robust mucosal immunity directly at the site of infection, with the implicit long-term strategic goal of creating a single-dose combination vaccine for both RSV and influenza. This approach could address significant public health needs for convenience and compliance, particularly in older adult populations who face a substantial disease burden from both co-circulating viruses.

The clinical development program for RSV/Flu-01E has progressed through a Phase 1 trial in adults (NCT05970744) and a Phase 2 trial in older adults (NCT06890429), both of which are reported as completed. However, a critical and defining feature of this program is the complete absence of publicly available, peer-reviewed clinical data. This "data void" presents an insurmountable obstacle to any rigorous, independent assessment of the vaccine's safety, immunogenicity, or efficacy. While preclinical studies were reportedly positive, this lack of transparency stands in stark contrast to the data-rich development programs of Western competitors and raises significant questions about the trial outcomes.