Durable humoral immunity and long-term protection induced by a Crimean-Congo hemorrhagic fever virus replicon particle vaccine in mice.

A Crimean-Congo hemorrhagic fever virus replicon particle vaccine was evaluated for long-term immunity and efficacy in mice. IgG responses persisted up to 18 months, with similar titers across dosing strategies through 12 months. Protective efficacy reached ≥75% at 6 months (prime-only) and up to 12 months (prime-boost). Booster dosing enhanced antibody avidity, effector function, and improved long-term protection. These findings support durable immunity from single or boosted vaccination.