Firm says weakened smallpox vaccine has good safety profile

Lisa Schnirring

Nov 14, 2008 (CIDRAP News) Bavarian Nordic, a Danish pharmaceutical company, announced recently that a smallpox vaccine that it is developing for people with weakened immune systems showed promising safety results in a phase 2 clinical trial involving volunteers with HIV infections.

In June 2007 the US Department of Health and Human Services (HHS) awarded the company a $500 million contract for 20 million doses of the vaccine, called Imvamune. It uses modified vaccinia Ankara (MVA), a virus that has been weakened so it can't replicate in humans. The conventional smallpox vaccine uses live vaccinia virus, which is related to the smallpox virus and can cause rare but potentially life-threatening side effects.

HHS has stockpiled enough conventional smallpox vaccine to protect the entire US population, but it estimates there are 10 million people who have limited immunity because they have conditions such as HIV or are undergoing chemotherapy.

The Imvamune study included 300 people with HIV infections and 86 healthy subjects, none of whom had a history of smallpox vaccination, Bavarian Nordic reported in a Nov 5 press release. The HIV group had CD4 counts between 200 and 750 cells per microliter.

Investigators found no difference between the two groups in adverse events, even among people who had the poorest immune status (CD4 counts of 200 to 350 cells per microliter).

Bavarian Nordic said Imvamune trials have now included more than 2,200 people in 11 complete or ongoing clinical studies, including a large portion of immunocompromised people, such as those with HIV infections or atopic dermatitis.

The company said it would report complete data from the trial in the second half of 2009. The findings will include immunogenicity data, long-term (6-month) safety information, and findings from an additional study arm involving patients with HIV infections who were previously exposed to a conventional smallpox vaccine, according to the release.

The company also said that within the next few days it would submit the initial phase 2 safety findings to the Food and Drug Administration, which will trigger a $25 million milestone payment under the HHS contract.