As a few vaccines inch closer to approval, experts warn that it may leave the recipients not feeling too well.
In a CDC meeting, a physician said the vaccine will not "feel wonderful" after injection.
Many vaccine trial participants reported flu-like symptoms after immunization.
Now health experts said this is the appropriate immune response to a vaccine working.
But they're worried because of this, people won't want to get the vaccine or come back for a second dose if needed.