Influenza update: vaccine development and clinical trials

Although influenza activity throughout the world has been relatively low during the past year, epidemics of influenza A, in particular, which are caused by new virus variants, continue to be a major public health problem. Widespread vaccination is the only rational measure that can be used for the prevention of illness in key risk groups. Although current inactivated split/subunit vaccines are reasonably effective, significant improvements have been shown to be possible in the boosting of responses by the use of particular adjuvants and/or the direct administration of vaccines to the respiratory tract. Live attenuated vaccines, also administered directly to the respiratory tract, have continued to be shown to be safe and effective, and, in the longer term, probably will have a major role in influenza prophylaxis, especially in children and young adults.