Vaccines against swine flu have already been developed in laboratories around the world, but will not be readily available until at least October and perhaps as late as December.

Around the world pharmaceutical companies have been producing vaccine strains for at least a month. Some are in the experimental stages, while others are approaching the need for clinical trials. However they are “by no means” ready yet, according to the World Health Organisation.

The UK's Department of Health has said it has signed contracts to supply enough vaccines for the entire British population and expects the first batches to arrive in the “early autumn”.

In April, the race to produce a successful vaccine against H1N1 began in earnest, when, under orders from the WHO, institutes in the UK, the US, Japan and Australia began work to produce a “seed strain” of the virus, which could then go on to provide for a vaccine.

In the UK, scientists at the Health Protection Agency's National Institute for Biological Standards and Control (NIBSC) in Potters Bar, Hertfordshire, began work on a strain isolated from a patient in the US.

Using a technique called “reverse genetics” the scientists took the genes that make the outer coating of the swine flu virus and then attached them to a harmless human virus known as PR8.

This reconstructed virus is considered safe for humans and will trigger an immune response that protects people against the swine flu strain.

— The Guardian, London