Abstract
Smallpox vaccines based on replicating vaccinia virus are known to elicit rare yet serious adverse events, particularly in human populations with immune deficiency, atopic dermatitis and at the extremes of age. A vaccine that induces protective immune responses equivalent to first-generation smallpox vaccines while reducing the risk for severe adverse events is critical for a national stockpile of smallpox vaccines. Modified vaccinia Ankara (MVA) has been proposed as an immediate solution for vaccination of high-risk individuals. Bavarian Nordic's vaccine MVA-BN (IMVAMUNE) is a MVA strain that is replication incompetent in mammalian cell lines. IMVAMUNE has been administered to more than 1900 human subjects to date, including high-risk populations (e.g., people diagnosed with atopic dermatitis or infected with HIV) in which standard replicating vaccines are contraindicated. We review the Phase I clinical trial safety profile and immune responses and compare them with other smallpox vaccines, including ACAM2000 and Dryvax.