Though many early vaccines worked well, side effects were always a concern, sometimes because the virus was still infectious, sometimes because proteins were present that triggered severe immune reactions. (newscientist.com)
Healthy monkeys died from severe immune reactions after «doping» with the EPO gene. (science.howstuffworks.com)
Histological analysis of the brain tissue is performed and shows no sign of severe immune reaction to the implant. (csne-erc.org)