> health experts say using a placebo poses ethical issues because the group receiving it will not know if they are actually protected against the illness. Ther

> health experts say using a placebo poses ethical issues because the group receiving it will not know if they are actually protected against the illness. There's also the ethical issue of giving a bunch of people an intervention that doesn't do anything, other than create various side-effects. Obviously if you're tweaking strains in the annual flu vaccine there's no need to go back to the drawing board. Just tweak and inject. But if you're testing a new vaccine technology, it would be nice to know it's more effective than salty water.