Astudy was done to see whether a smaller dose of flu vaccine could be used successfully. in this study, the usual amount of vaccine was injected into half the patients, and the other half of the patients had only a small amount of vaccine injected. the response was measured by looking at the production of antibodies. in the end, the lower dose of vaccine was just as effective as a higher dose for those under 65 years old. what more do we need to know to be able to conclude that the lower dose of vaccine was equally effective at preventing the flu for those under 65?