The aim of this Focus issue is to highlight some of the most recent examples of the progress that has been made in developing vaccines for diseases that disproportionately affect the developing world.

Vaccines are among the most cost-effective tools for reducing the morbidity and mortality associated with infectious diseases and, as Almond points out in the Foreword (page 478), there has been a quiet renaissance in vaccine research and development in recent years. Kaufmann (page 491) and Guy (page 505) provide the groundwork, summarizing the advances in our understanding of the immune response that should facilitate the development of new antibacterial vaccines and adjuvants, respectively. Whitehead and colleagues (page 518) give an update on the quest to develop a dengue vaccine, a goal that will hopefully be achieved in the next few years. This goal has already been reached for rotavirus, and Angel and co-workers (page 529) address the outstanding questions that remain about the two recently licensed rotavirus vaccines. For shigellosis, a vaccine remains elusive, and Levine and colleagues (page 540) consider the lessons that can be learned from more than 40 years of intensive research. In their Opinion article (page 555), Welsh and Fujinami question the wisdom of designing vaccines against viral diseases using just a small number of epitopes. Finally, this issue would not be complete without considering the three biggest killers. Accordingly, in our News & Analysis section, Nabel, Andersen, and Todryk and Hill each provide a short Vaccine watch article that gives a précis of the current state of play of vaccine development for HIV/AIDS, tuberculosis and malaria, respectively.

As usual, this Focus issue is accompanied by a Web Focus (http://www.nature.com/nrmicro/focus/vaccines), an online collection of recent articles on vaccines published in Nature Publishing Group journals.