The impact of RSV/SARS-CoV-2 co-infection on clinical disease and viral replication: insights from a BALB/c mouse model.

Infants and young children are commonly affected by respiratory viral co-infections. While RSV and SARS-CoV-2 are two of the most prevalent respiratory viruses, their co-infection rate in children remains surprisingly low. In this study, we investigate the impact of RSV/SARS-CoV-2 co-infection on clinical disease and viral replication using an animal model. The findings indicate that RSV infection either simultaneously or prior to SARS-CoV-2 infection in mice protect against SARS-CoV-2-induced clinical disease and viral replication. On the other hand, infection with SARS-CoV-2 followed by RSV results in worsening of SARS-CoV-2-induced clinical disease, but also protection from RSV-induced clinical disease. These results highlight a protective role for RSV exposure, given this occurs before infection with SARS-CoV-2. This knowledge could help guide vaccine recommendations in children and sets a basis for future mechanistic studies.