A global race to prepare a vaccine against swine flu was under way yesterday as health officials confirmed that the disease had spread to at least seven countries.
The World Health Organisation has contacted vaccine manufacturers, who are on standby to produce the vaccine should the virus continue to spread.
A WHO spokesman said it had not yet advised pharmaceutical companies to begin producing a vaccine, but he confirmed that work had already begun at collaborating laboratories in the US.
British scientists at the Health Protection Agency's high containment laboratories in Potters Bar, north London, are due to receive samples of the fresh virus today. They will spend the next three to four weeks making it safe but it will take a further three to five months before it will be ready as a vaccine.
It is likely that the WHO would raise the threat level of the flu outbreak to phase five before ordering a vaccine to be made. A phase five alert means the virus is spreading freely between humans in at least two countries in one WHO region, a strong indication that a pandemic is imminent.
On Monday night, the threat assessment was upgraded from three to four, as it became clear the disease was causing "community-level outbreaks".
In Britain, the pharmaceutical company GSK will take the lead in manufacturing the new vaccine under a "sleeper contract" with the Department of Health. The contract is agreed in advance to avoid tendering delays in the event of a global pandemic.
The Centres for Disease Control and Prevention in Atlanta, Georgia, has isolated the swine flu virus from a patient in California and work is under way to make it usable by vaccine manufacturers. It could take between four and six months to make a vaccine.
The US lab will receive support from scientists at the HPA's National Institute for Biological Standards and Control in Potters Bar. A specialist courier used to handling infectious material is due to deliver to them a sample of the California swine flu strain today or tomorrow. "It's too risky to depend on just one laboratory making these viruses, you need to have back-up. If for some reason, the CDC has a problem with this, we're there," said John Wood, a principal scientist at the Potters Bar lab.
The virus will be transferred to a high security room at the lab and disassembled using a technique called "reverse genetics". Scientists will then take the genes that make the swine virus's outer coating and attach them to a harmless human virus called PR8. This reconstructed virus is safe for humans, but triggers an immune response that specifically protects against the swine flu strain.
Wood said there was some concern over pharmaceutical companies being able to manufacture any new vaccine while still making enough seasonal flu jabs for the coming winter. Most have already begun and would have to halt production before switching to a new vaccine.
"This is the difficulty with all flu manufacturers at the moment," said Wood. "They are two months into production, and if they have to stop now, there could be shortages of the seasonal vaccine in the winter."
A spokesman for GSK confirmed that discussions were taking place between the company, WHO and the CDC about a vaccine for swine flu, but refused to elaborate on its strategy for making enough of both vaccines. "We have a lot of product capacity around the world and we have a flexible approach to moving things around," he said. The company has sent 170,000 doses of its seasonal flu vaccine to Mexico at the request of local health officials.
WHO has also contacted Novartis, the Swiss pharmaceutical company, about its ability to make swine flu vaccine at its plant in Liverpool. The facility produces a small amount of seasonal flu vaccine for Britain, but most is exported to the US.
"We are in the middle of producing flu vaccine for next season, and we'd have to stop that before we can start making another vaccine. It's not that there is spare capacity just waiting there for a pandemic to happen," a Novartis spokesman said.
WHO may consider adding a swine flu component to the seasonal vaccine in time for a second wave of infections that many scientists expect to strike in the autumn.
The seasonal flu vaccine protects against three strains of influenza virus, and each component has to be grown in a hen's egg, meaning three eggs are needed to make one flu jab. The swine flu vaccine is expected to protect against only one strain, so only one egg will be needed for each shot.