142 Vaccines

under the pressure placed on it by a pandemic. Vaccines may only be available for the second wave of the pandemic, which tends to have a higher mortality than the initial wave.

If the pandemic starts in a year’s time, it is likely that we will then have some experience in developing mock vaccines, so that a vaccine could be produced relatively quickly using a variety of the technologies currently under investigation. There would still be a significant delay, and it is likely that there would still be insufficient quantities, with rationing required.

We don’t know when a pandemic will occur – but starting preparation now is essential. If the pandemic is delayed by a few years, we may well have the required vaccine production capacity to minimise the disastrous consequences.

Solutions

The WHO suggests various strategies to solve these problems (WHO 2005d) and is working with governments, scientists, vaccine and drug companies, and other role players around the world to achieve a solution.

Strategies for expediting the development of a pandemic vaccine

Shorten the time between emergence of a pandemic virus and the start of commercial production.

1.Candidate “pandemic-like” vaccines need to be made and put through trials. This will require adopting a centralized evaluation team to examine the findings of the studies and give clearance for the use of the vaccine. It would not be feasible for each medicine’s evaluation team to do this for their own country. The vaccine needs to become established through “mock” trials in order to be able to be expedited in this way – then, like the current influenza vaccine, it is known, and only brief studies are required to confirm immunogenicity and safety.

2.Increased production capacity must be developed worldwide – for example, changing to cell culture vaccines. Another important means to improve production is to increase consumption – using more of the current vaccine today will not only decrease the burden of current influenza disease, as well as helping to prevent reassortment in humans infected with two strains of virus, but will ultimately enable production to be increased.

Enhance vaccine efficacy

1.Antigen sparing methods, such as intradermal injection, need to be researched more thoroughly, as they provide for a potential saving in antigen – the 1 µg of

antigen (per strain) in current vaccines could be lowered considerably. If we could use one 8th of the dose, our current 900 million monovalent doses could be expanded to 7.2 billion doses – enough for 3.6 billion people, more than half of the world’s population (Fedson 2005).

2.Adjuvants need to be evaluated – if immunogenicity can be enhanced, less antigen would be required for a protective immune response.