can outpace the immune system. developing a mature immune response to a vaccine may require months, but some cancers (e.g. advanced pancreatic) can kill patients in less time. many cancer vaccine clinical trials target patients' immune responses. correlations typically show that the patients with the strongest immune responses lived the longest, offering evidence that the vaccine is working. an alternative explanation is that patients with the best immune responses were healthier patients with a better prognosis, and would have survived longest even without the vaccine. recommendations in january 2009, a review article made recommendations for successful oncovaccine development as follows: target settings with a low disease burden. conduct randomized phase ii trials so that the phase iii program is sufficiently powered. do not randomize antigen plus adjuvant versus adjuvant alone. the goal is to establish clinical benefit of the immunotherapy (i.e., adjuvanted vaccine) over the standard of care. the adjuvant may have a low-level clinical effect that skews the trial, increasing the chances of a false negative. base development decisions on clinical data rather than immune responses. time-to-event end points are more valuable and clinically relevant. design regulatory into the program from inception; invest in manufacturing and product assays early.