Bavarian Nordic has delivered one million doses of its Imvamune smallpox vaccine to the US Strategic National Stockpile as part of the country’s preparations against a potential bioterrorism attack.

The vaccine is a non-replicating strain of vaccinia virus which, unlike conventional smallpox vaccines, cannot replicate in human cells, thereby eliminating the risk of accidental infection.

Current smallpox vaccines are considered a risk to up to 25% of the population, who may be immunocompromised or have other medical conditions that could make the vaccine dangerous.

Imvamune is the first vaccine successfully developed under Project BioShield, the programme created by Congress in 2004 to develop and purchase medicines and vaccines to guard against bioterror agents.

It was clinically developed and manufactured under contracts with the National Institutes of Health and Biomedical Advanced Research and Development Authority (BARDA), a division of the US Department of Health & Human Services.

Under the BARDA contract, Bavarian Nordic will deliver 20 million doses of Imvamune to the US Strategic National Stockpile, with an option for 60 million more.