Vaccines were created to protect us from pathogens ranging from influenza and measles to smallpox, polio, and diphtheria. But vaccines to some pathogens—like HIV and the herpes simplex virus (HSV)—have repeatedly failed in clinical trials. In the lone successful HIV vaccine trial to date, the vaccine only provided slight protection over the placebo. And GlaxoSmithKline (GSK) reported last year that its promising HSV2 vaccine against genital herpes sputtered in a large, late-stage trial.
Most vaccines provide the immune system with key pathogen-derived molecules to help it later recognize and attack the same intruder. But many of the molecules are, by themselves, “not really capable of provoking strong immune responses,” explained Dennis Klinman, an immunologist at the National Cancer Institute.