
Phase II Vaccine Trials
In the second phase, scientists go from up to 80 subjects to several hundred. It’s also during this phase where they’ll look at people who may have some underlying health problems, so they learn of any risks with the disease and vaccine. The subjects in this phase don’t know if they are in the placebo group or received the vaccine. The trials are all randomized but also controlled.
Other than safety, other goals of phase II include immunogenicity, schedule of immunizations, proposed doses, and method of delivery. Once phase II is proven successful, which can take up to several months, the scientists move on to the next step.