Recent years have seen unprecedented outbreaks of avian influenza A viruses. In particular, highly pathogenic H5N1 viruses have not only resulted in widespread outbreaks in domestic poultry, but have been transmitted to humans, resulting in numerous fatalities. The rapid expansion in their geographic distribution and the possibility that these viruses could acquire the ability to spread from person to person raises the risk that such a virus could cause a global pandemic with high morbidity and mortality. An effective influenza vaccine represents the best approach to prevent and control such an emerging pandemic. However, current influenza vaccines are directed at existing seasonal influenza viruses, which have little or no antigenic relationship to the highly pathogenic H5N1 strains. Concerns about pandemic preparedness have greatly stimulated research activities to develop eff- tive vaccines for pandemic influenza viruses, and to overcome the limitations inh- ent in current approaches to vaccine production and distribution. These limitations include the use of embryonated chicken eggs as the substrate for vaccine prod- tion, which is time-consuming and could involve potential biohazards in growth of new virus strains. Other limitations include the requirement that the current inac- vated influenza vaccines be administered using needles and syringes, requiring trained personnel, which could be a bottleneck when attempting to vaccinate large populations in mass campaigns. In addition, the current inactivated vaccines that are delivered by injection elicit limited protective immunity in the upper respiratory tract where the infection process is initiated.

Pandemic Influenza Overview

Pandemic Influenza as a Current Threat
Antigenic Cross-Reactivity Among H5N1 Viruses
Current Approaches for Human and Avian Vaccine Production
Seasonal Influenza Vaccines
Generation and Characterization of Candidate Vaccine Viruses for Prepandemic Influenza Vaccines
Live Attenuated Vaccines for Pandemic Influenza
Influenza Vaccines for Avian Species
Development and Application of Avian Influenza Vaccines in China
Novel Vaccine Approaches
Designing Vaccines for Pandemic Influenza
Attenuated Influenza Virus Vaccines with Modified NS1 Proteins
DNA Vaccines Against Influenza Viruses
Recombinant Proteins Produced in Insect Cells
Influenza Neuraminidase as a Vaccine Antigen
Recombinant Vectors as Influenza Vaccines
Influenza Virus-Like Particles as Pandemic Vaccines
Pandemic Influenza Vaccines
Adjuvants for Pandemic Influenza Vaccines
Novel Approaches for Vaccine Delivery
Transcutaneous Immunization with Influenza Vaccines
Microneedle-Based Vaccines
Vaccine Evaluation, Production and Distribution
Animal Models for Evaluation of Influenza Vaccines
Immunosenescence and Influenza Vaccine Efficacy
Vaccines for Pandemic Influenza: Summary of Recent Clinical Trials
Considerations for Licensure of Influenza Vaccines with Pandemic and Prepandemic Indications
Strategies for Broad Global Access to Pandemic Influenza Vaccines
Prioritization of Pandemic Influenza Vaccine: Rationale and Strategy for Decision Making.