A single injection of unadjuvanted vaccine could provide adequate immunity to protect most people during the expected influenza A (H1N1) pandemic, an early study suggests. The findings published in September (N. Engl. J. Med. 361, 2009, doi:10.1056/NEJMoa0907413) suggest vaccine stockpiles could go twice as far as originally predicted, potentially allowing health authorities around the world to reduce their vaccine orders. So far, the US Health and Human Services Department, which has ordered over $1.4 billion in nonadjuvanted H1N1 vaccines, has left manufacturing contracts and vaccination plans unchanged. “We have the ability to deliver 251 million doses of vaccine,” said Tom Skinner, a spokesperson for the Centers for Disease Control and Prevention in Atlanta, Georgia. “We just don't know what the demand will be.” In September, the US Food and Drug Administration cleared four H1N1 vaccines produced following the same egg-based process as seasonal flu strains (Nat. Biotechnol. 27, 489–491, 2009). Vaccine manufacturers expect to meet the demand for the US vaccination campaign, which began mid-October, following a two-dose schedule. European authorities have licensed two adjuvanted and one nonadjuvanted vaccine. They anticipate reviewing the current primer and booster schedule in coming months pending results from single-shot vaccination trials.