ACAMBIS, the Cambridge-based drugs company that supplies the US government with smallpox vaccines to protect the population against biological attack, today suspended trials on the medicine after finding serious side-effects among some volunteers.
With the US on high terrorist alert, it fast-tracked orders for 209 million doses of the drug from Acambis before it had been fully tested.
Now, intense monitoring has discovered that some of those used in the test suffered a major heart condition. The drug has not been given to anybody outside the trials.
Acambis, headed by chief executive Gordon Cameron, is one of many drugs companies attempting to make a safer version of the only licensed existing vaccine, Dryvax, which has been used for generations. Despite its efficacy, Dryvax's manufacture, from calves' bellies, is seen as dated.The company's Acam2000 is a chemically produced version of the vaccine given by injection.
Acambis was one of the companies that lost out in the bidding for the contract to provide vaccines for Britain. That deal was controversially won by PowderJect, whose founder Paul Drayson was a major Labour Party donor.
Smallpox was eradicated in 1971 after a worldwide Dryvax vaccination and quarantine programme organised by the World Health Organisation.
But the threat of biological weapons use by rogue states and terror organisations has led most first-world governments to stock up on unlicensed vaccines to give to the public in the event of an attack.
The military and front-line medical workers vaccinated since 9/11, considered most likely to come into contact with the disease, have been given Dryvax from old stock.
Shares in the group fell 41 1/2p to 322 1/2p on the news.
• THE threat from terrorists has led governments around the world to rush out orders for stockpiles of smallpox vaccines, none of which has been fully licensed.
As part of its contract with the US, Acambis was asked to get the drug through the normal trials required for other drugs and prove that it was as effective as Dryvax, its predecessor.
The problems now appearing in the Phase III trials were anticipated because heart conditions had been noticed in previous Dryvax vaccination programmes.
It is unclear whether the findings reported today are down to the intensive monitoring now being conducted into Acam2000 or the product itself.
The smallpox vaccine drawn from calves' bellies was invented in the 1890s when a scientist, Edward Jenner, spotted that milkmaids were less prone to the disease than the rest of the population.