The British Medical Journal published a paper that revealed a correlation between the administering of the A/H1N1 2009 influenza vaccine and an increased risk of narcolepsy in children and adolescents in England. The study, conducted by researchers from the Health Protection Agency and two Cambridge hospitals, confirmed previous findings from Finland and Sweden which first suggested this possible association in 2010 and 2012. Narcolepsy is a chronic neurological disorder characterized by disturbed nocturnal sleep, abnormal daytime sleep pattern and sudden muscular weaknesses caused by strong emotions, that may possibly lead to total collapses.
«The increased risk of narcolepsy after vaccination with ASO3 adjuvanted pandemic A/H1N1 2009 vaccine indicates a causal association, consistent with findings from Finland,» wrote the authors of the study. «Because of variable delay in diagnosis, however, the risk might be overestimated by more rapid referral of vaccinated children.» 

BMJ paper: http://www.bmj.com/cgi/doi/10.1136/bmj.f794