The stop smoking vaccine NicVAX had some success in its initial tests and phase II trials, but failed both of its more-intensive phase III clinical trials in 2011. The vaccine's side effects included colds, headaches and upper respiratory tract infections. A smoking vaccine remains in development, as of 2015.
The initial tests of NicVAX involved injections into lab rats, which cut nicotine levels in the brain. Phase II of the trials, which used human patients, demonstrated that of the patients with a high anti-nicotine antibody response, a significantly higher percentage abstained from smoking after the NicVAX injection. However, phase III had a larger sample size and followed patients for a longer time period. Patients in this trial had similar success rates whether or not they received the vaccine.