A paradigm shift in vaccine production for pandemic influenza

The recent introduction of an H5N8 subtype highly pathogenic avian influenza virus (HPAIV) into the United States from Asia is a timely reminder of the propensity of avian influenza viruses to undergo rapid global movement. The subsequent reassortment of this virus to generate an H5N2 subtype variant, which has caused significant mortality in commercial poultry across America, similarly highlights the potential of HPAIV to change quickly and unpredictably. Concurrent with the introduction of H5N2 subtype influenza into the US, H7N9 subtype avian influenza virus continues to circulate in birds in China and to cause associated zoonotic infection of humans, with a high case fatality rate in confirmed cases. Although the incidence of human infections with H7N9 is relatively low, the outbreak has persisted for more than 2 years and spread throughout Eastern China, a region with large areas of high human population density. Given the current high case fatality rate, if the H7N9 virus were to acquire the ability to transmit efficiently in humans, its subsequent emergence into an immunologically naïve population would likely require a major global public health response.