Gates Package — page 1035

te's safety and studying Preclinical studies. A year or two assessing your candidate's safety and studying whether it actually triggers an immune response in animals. Phase 1 trials. If you get permission from your government's regulator to run clinical trials in humans, you'll start a small one involving a few dozen volunteers, some of whom also get a placebo. At this point you're just looking to see if it causes any adverse effects. Phase 2 trials. You'll give the vaccine candidate to several hundred people and measure whether it's safe, check whether it bolsters their immune systems in the right way, and calculate the proper dosage. Phase 3 trials. You'll run even larger trials involving thousands or tens of thousands of people, half of whom get a placebo or the most effective vaccine that's currently available. In Phase 3, you want to do two things, both of which require lots of volunteers from various communities where the disease you want to block is prevalent. One goal is to prove that the vaccine significantly reduces disease when compared with a placebo. Once the trial is under way, you have to wait until you have enough cases of sickness to know whether most of the infections are among people who get the placebo rather than those who get the vaccine. The other goal in this phase is to identify relatively rare bad side effects, which might show up in, say, one in every 1,000 cases. So even with 10,000 participants, you'll see the side effect in just 10 of them. Just as in a drug trial, you'll also need a diverse pool of volunteers from both sexes and different communities, races, ethnicities, and age groups. Stephaun Wallace, an epidemiologist at Fred Hutch in Seattle, is one of many people around the world who are trying to deepen the pool of potential volunteers.