Replicating RNA vaccine confers durable immunity against Crimean Congo hemorrhagic fever virus challenge in mice.

Spread by Hyalomma genus ticks, Crimean-Congo hemorrhagic fever virus (CCHFV) causes a severe hemorrhagic disease endemic throughout Southern and Eastern Europe, Asia, and Africa. To date, there are no widely approved vaccines for CCHFV and treatment for disease is largely supportive. Due to this lack of intervention, the WHO lists CCHFV as a high-priority pathogen. Recently, we described a highly efficacious self-replicating RNA vaccine which is protective against CCHFV disease in mice and non-human primates. This vaccine induces high titers of non-neutralizing anti-nucleoprotein (NP) antibodies and a robust T-cell response against the viral glycoprotein. Here, we assess the durability of this vaccine in mice by monitoring the immunogenicity and efficacy of this vaccine up to 1 year post vaccination. We found that while glycoprotein-specific T-cell responses and anti-NP antibody titers waned over time, mice remained protected against lethal CCHFV challenge for at least 1 year post vaccination.