The first influenza pandemic of the 21st century, due to a new strain of A(H1N1) virus, was declared on 11 June 2009 by the Director-General of the World Health Organization. Fortunately, the international community, including influenza vaccine manufacturers, has been increasing its preparedness for such an event, triggered by the need to stem the spread of the highly pathogenic avian influenza A(H5N1) virus over recent years. Today, the development of a pandemic influenza vaccine in the fastest possible time is a global priority. However, two major issues need to be taken into consideration: how long will it take to produce sufficient pandemic vaccine doses to immunize the global population at risk, including poor populations that have no resources to purchase the vaccine; and how will pandemic vaccine production affect availability of trivalent vaccine for the forthcoming 2009-2010 influenza season. To address these questions, WHO carried out a survey in May 2009 among influenza vaccine manufacturers on their planned seasonal and pandemic production with a view to developing recommendations on the distribution and use of pandemic influenza vaccine.