Vaccination is the best option by which to prevent the spread of a pandemic virus and reduce the severity of disease. Defi ning the host response to infl uenza (H5N1) in natural infection is urgently needed to better understand the basis of protection and subsequent development of effi cacious vaccines. Improved vaccine strategies, which will require less antigen and be more robust in inducing both antibody and cell-mediated immunity for neutralizing infl uenza (H5N1) viruses, should be considered. To create an effective vaccine, a combination of factors must be optimized-such as number of doses, formulation without or with better adjuvant, and dose range. We also need to develop a reproducible assay that measures immunogenicity of a vaccine and to establish adequate correlates of protection. The effi cacy of potential cross-reactive vaccine candidates to induce broad-spectrum immunity to infl uenza (H5N1) viruses should be assessed critically; stockpiling of such vaccines may be justifi ed in the absence of optimally matched and approved vaccine during early stages of an H5 pandemic. Search for therapeutic vaccines (antidisease vaccines) aimed at controlling innate immune responses should be pursued, given the clinical evidence that the H5N1 subtype elicits a cytokine storm that contributes to disease pathogenesis. Vaccine development and deploy-ment need to be undertaken by a partnership of academia, government, and industry. The risk for dissemination of pandemic virus will remain if the disease is controlled in 1 area but not in others. A global approach is vital for combating the next infl uenza pandemic, a monumental public health challenge. Global Public Health Security National public health institutes will play a key role in implementation of the revised International Health Regulations. from transnational health threats demands a global public health perspective and investment in global public health infrastructure. The theme of this year's World Health Day and the World Health Report 2007 is "Global public health security-the need to reduce the vulnerability of people around the world to new, acute, or rapidly spreading risks to health, particularly those that cross international borders" (5) . With a call to all nations to "invest in health, and build a safer future," the World Health Organization (WHO) emphasizes the need for collaboration among nations to increase our collective capacity and infrastructure to respond to potential international health emergencies and other public health risks. As recent events have shown, global public health security is a complex, costly, and information-intense undertaking that requires strong national public health leadership and infrastructure, cross-border collaboration, capacity to identify problems rapidly and design real-time evidence-based solutions, well-trained and well-equipped workforces, well-functioning laboratories and service-delivery systems, capacity to sustain interventions, and ability to respond to unexpected events (5, 6) . Investment in these elements will strengthen not only global public health security but also the infrastructure needed to help broaden access to healthcare services and improve individual health outcomes, which would help break the cycles of poverty and political instability and thus contribute to national economic development and achievement of the Millennium Development Goals (7) .