by Olivia Elsom

Created on: May 10, 2009   Last Updated: December 28, 2009

Although it requires the involvement of some of our top scientific minds and weeks of painstaking work, the creation of a flu vaccine starts in the simplest of ways with an ordinary chicken egg, a little bit of virus, and a scientist with a drill and a steady hand!

It's an old technology that's been used for decades but eggs make excellent production factories, and are perfect for growing flu viruses. Scientists drill a tiny hole in the egg and  then carefully inject a small amount of live flu virus into it. All this takes place in a tightly controlled environment to avoid contaminating the vaccine at this crucial stage of development. After a few days of incubation the process moves on to the next stage.

A number of techniques can then be used but the second stage usually involves taking the H and N proteins from the virus and mixing them with a laboratory virus known as PR8 to create a harmless hybrid virus which can be used for the vaccine. This process is known as reverse genetics. Alternatively, the H1N1 virus and the PR8 lab virus can both be injected directly into the same egg, allowing the hybrid virus to develop through the genetic processes which take place within the egg.  The creation of this first batch of vaccine, which is known as seed strain, will usually take about three or four weeks.

The recent appearance of the new variant of swine flu created a flurry of activity in influenza centres around the world but creating the vaccine is just the first step.  It is then necessary to test its effectiveness and, of course, safety before it can be manufactured and distributed to the general population.   Clinical trials of the swine flu vaccine began in July 2009 where it was administered to healthy adult volunteers in a number of countries including Australia and the United States.  One of the advantages scientists had with this latest flu variant is that the vaccine for swine flu very closely resembles existing vaccines for other pandemics, all of which have been previously tested for safety.    

However, the vaccine then needed to be produced in bulk.  It will normally take vaccine manufacturers four or five months before they can produce sufficient quantities for an immunisation programme.  Flu vaccines have to be produced all the time and, at the time swine flu first emerged as a cause for concern, vaccine manufacturers were in the process of producing routine seasonal flu vaccines.

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