Iain Stephenson has worked on aspects of influenza at the Centers for Disease Control (CDC) in the United States and is now consultant in Infectious Diseases at Leicester Royal Infirmary.
Along with his colleague Professor Karl Nicholson he has worked to test trial vaccines against strains of avian influenza that have shown the ability to infect humans as well as birds.
He explained to Panorama that one of the biggest problems to creating a pandemic vaccine was manufacturing capacity.
In the event of a pandemic influenza, worldwide vaccine demand would soar, but current manufacturing capacity is only around 300 million doses of vaccine a year which is a small percentage of the world's population.
Large amounts of influenza virus are needed to produce vaccine, and this key ingredient must be grown up in eggs.
Studies conducted by the Leicester team have focussed on ways of improving the body's response to vaccines to generate a healthy immune response in each patient without using up more of the virus than is necessary.
So far, clinical trials of H5 vaccine have shown that you need a much larger dose than usual to get to a point of immunity, in comparison to the dose of virus in normal influenza vaccines.
In fact you need two shots rather than one. This is because people have had no exposure to a pandemic strain at all and have no immunity to it.
All of this will place a strain on capacity which will mean a longer wait during a pandemic. As Iain explained to Panorama:
Come a pandemic, everyone is going to be struggling around looking for their vaccine. Manufacturing capacity is certainly limited, that needs to be built up over a period of time and there has to be investment to do that.
The government's already put out a tender for Avian flu vaccine for stockpiling. The problem with this is that at the moment we don't know what dose of vaccine we're going to need, nor how many doses are going to have to be given.