Bird Flu Vaccine Research and Development, Current Status

Vaccines are considered the first line of defence for reducing the excess morbidity and mortality that invariably accompany pandemics. For several reasons, no country will have adequate supplies of vaccine at the start of a pandemic and for many months thereafter. Large-scale commercial vaccine production is not expected to commence until about three to six months following the emergence of a pandemic virus.


Manufacturing capacity for influenza vaccines is overwhelmingly concentrated in Europe and North America. Current production capacity - estimated at around 300 million doses of trivalent seasonal vaccine per year - falls far below the demand that will arise during a pandemic.


WHO, through its network of specialized influenza laboratories, has constantly monitored the evolution of the H5N1 virus since its initial infection of humans in Hong Kong in 1997. These laboratories prepare the prototype vaccine strain that is being provided to industry as the "seed" for vaccine development. Constant molecular analyses of viruses, conducted by these laboratories, help ensure that work on vaccine development stays on track. This is particularly important in view of mutations in the virus detected during 2005.


Around 10 countries have domestic vaccine manufacturers, and several of these are presently working on the development of a pandemic vaccine. Some of these development projects have reached the stage of clinical trails; clinical trials of other candidate vaccines are expected to begin shortly. One company has indicated that it will be presenting the results of its clinical trials to WHO by early December 2005. However, if a pandemic were to begin within the next few months, no company would be ready to move immediately into commercial production.


At present, little knowledge exists to guide formulation of an influenza vaccine that is both effective and economizes on the use of antigen - the component of the vaccine that elicits the immune response. However, clinical trials are under way to test different formulations, and these trials will provide some answers. WHO has encouraged companies to test vaccine formulations that include an adjuvant. This substance boosts the immune response, and theoretically could allow adequate protection at lower quantities of antigen. Work on this approach is also under way.


As a pandemic vaccine needs to be a close match to the actual pandemic virus, commercial production cannot begin prior to emergence and characterization of the pandemic virus. WHO has, however, encouraged industry and regulatory authorities to develop fast-track procedures for licensing and marketing authorization of a pandemic vaccine, and this has been done.


In addition, WHO is using international meetings to urge the international community to find ways to increase manufacturing capacity and ensure that developing countries have access to an effective vaccine at an affordable price. On current trends, however, most developing countries will have no access to a vaccine during the first wave of a pandemic and perhaps throughout its duration.


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