The side effects of the HiB vaccine are very mild and not very common. About 5 percent of children will have a low-grade fever up to 101ºF. Up to 25 percent of children will have redness, warmth, or swelling at the injection site. There have been no moderate or severe side effects noted for this vaccine at all. There was a concern in an Australian study that linked the HiB vaccine to an increased risk for juvenile diabetes, but additional research has failed to confirm that concern.