The declaration of pandemic alert Phase 6 for human influenza A (H1N1) by the WHO and the measures taken by individual countries in June 2009 has shown the world how fragile today's resources in pandemic and prepandemic, but also seasonal, vaccines are. Conventionally, human influenza vaccines are produced in embryonated chicken eggs. However, significant efforts of authorities and vaccine manufacturers over the last decade have led to the establishment of cell culture-derived vaccines. Currently, vaccines produced in three different host cell lines (Madin-Darby Canine Kidney, Vero and PER.C6) are in clinical trials, and the first licenses for seasonal as well as pandemic H5N1 vaccines have been granted. These encouraging developments for cell culture-based influenza virus production are summarized and an overview on potential cell substrates is given.