Shares in Acambis closed up nearly 5% at 115 pence on the London Stock Exchange yesterday as investors were pleased by news that US regulators have decided to use the group’s ACAM2000 as the country’s only smallpox vaccine.

ACAM2000 is a second-generation smallpox vaccine and derived from a clone of Wyeth’s Dryvax, which the US Food and Drug Administration licensed back in 1931. An important advantage with Acambis’ vaccine is that it is grown in cell cultures in the lab, while Dryvax is grown on the skin of calves and freeze-dried for storage, but is no longer manufactured and remaining supplies are limited.

ACAM2000 was approved in the USA in September last year, based on a clinical study that demonstrated its non-inferiority to Dryvax, although the FDA noted that about one in 175 healthy adults who received the vaccine for the first time developed myocarditis and/or pericarditis, though there were no fatalities.

According to the World Health Organisation, smallpox is believed to have originated over 3,000 years ago in India or Egypt, and is one of the most devastating diseases in history, killing as many as 30% of those infected. But global efforts in the 1960s to eradicate the disease proved a success, and the last single natural case was reported in Somalia in 1977.

However, the lethal and highly-contagious nature of smallpox makes it a perfect choice of biological weapon, and the purpose of the US government’s stockpile of a vaccine is to protect against a potential terror attack using the disease, which is still locked away in some labs for research.

Long-term supply
“The military needs the smallpox vaccine to inoculate troops against biological weapons that may contain the virus. Acambis will provide a long-term, stable supply of the vaccine manufactured within the United States,” commented Army Colonel Randall Anderson, Director of its Military Vaccine (MILVAX) Agency.

The US Centers for Disease Control and Prevention already has stockpiled 192.5 million doses of the vaccine, under a deal signed in 2001 with Acambis, and the FDA noted that the vaccine will not be available to the public commercially, but rather military personnel, emergency essential and equivalent civilian employees, and laboratory researchers working on certain pox viruses.

“We are delighted to see the Department of Defense relying on ACAM2000,” beamed Ian Garland, Chief Executive Officer of Acambis. “This is in line with our ongoing discussions to secure ACAM2000 production for the US for the long term,” he added.