Vaccines have made a major and increasingly important contribution to public health and have brought radical improvements in the prevention of disease throughout the world. For the majority of infectious diseases, vaccination is the most effective preventative measure. Public confidence is critically important for the successful implementation of national immunisation programmes, especially as vaccines are administered to large numbers of healthy, often young, individuals. NIBSC, as an Official Medicines Control Laboratory (OMCL) of the European Union, independently tests vaccines for release onto the EU market to ensure their continued safety and effectiveness from one batch to the next. This work is underpinned by a comprehensive research and development programme aimed at improving the assays used to assess licensed products and developing appropriate tests for novel vaccines.