Pandemic vaccines: promises and pitfalls.

Prototype vaccines against influenza A/H5N1 may be poorly immunogenic, and two or more doses may be required to induce levels of neutralising antibody that are deemed to be protective. The actual levels of antibody required to protect against a highly pathogenic virus that potentially can spread beyond the large airways is unknown. The global capacity for vaccine manufacture in eggs or tissue culture is considerable, but the number of doses that can theoretically be produced in a pandemic context will only be sufficient for a small fraction of the world's population, even less if a high antigen content is required. The safety of new pandemic vaccines should be addressed in an internationally coordinated way. Steps are underway through the Therapeutic Goods Administration to evaluate mock-up vaccines now, so that the time to registration of a new product can be minimised. It will be 3-6 months into the pandemic before an effective vaccine becomes available, so other control measures will be important in the early stages of a pandemic. The primary goal of a pandemic influenza vaccine must be to prevent death, and not necessarily to prevent infection.