Because of widespread distribution of the influenza A (H1N1) 2009 monovalent vaccine (pH1N1 vaccine) and the prior association between Guillain-Barré syndrome (GBS) and the 1976 H1N1 influenza vaccine, enhanced surveillance was implemented to estimate the magnitude of any increased GBS risk following administration of pH1N1 vaccine. The authors conducted active, population-based surveillance for incident cases of GBS among 45 million persons residing at 10 Emerging Infections Program sites during October 2009-May 2010; GBS was defined according to published criteria. The authors determined medical and vaccine history for GBS cases through medical record review and patient interviews. The authors used vaccine coverage data to estimate person-time exposed and unexposed to pH1N1 vaccine and calculated age- and sex-adjusted rate ratios comparing GBS incidence in these groups, as well as age- and sex-adjusted numbers of excess GBS cases. The authors received 411 reports of confirmed or probable GBS. The rate of GBS immediately following pH1N1 vaccination was 57% higher than in person-time unexposed to vaccine (adjusted rate ratio = 1.57, 95% confidence interval: 1.02, 2.21), corresponding to 0.74 excess GBS cases per million pH1N1 vaccine doses (95% confidence interval: 0.04, 1.56). This excess risk was much smaller than that observed during the 1976 vaccine campaign and was comparable to some previous seasonal influenza vaccine risk assessments.

Background:Acute exertional rhabdomyolysis has been infrequently reported among adolescents. In August 2010, several high school football players from one team developed rhabdomyolysis and triceps compartment syndrome following an upper arm exercise held in a non-air-conditioned wrestling room.Purpose:To confirm the diagnoses, characterize the spectrum of illnesses, and determine the factors contributing to rhabdomyolysis and triceps compartment syndromes.Study Design:Descriptive epidemiology study.Methods:The authors reviewed hospital medical records and interviewed players, coaches, school administrators, and hospital staff, using a standardized questionnaire that assessed symptoms, exposures, and activities.Results:Among 43 players, 22 (51%) experienced rhabdomyolysis (peak creatine kinase range, 2434-42 000 U/L): 22 patients had upper arm myalgia; 12 were hospitalized; 3 experienced triceps compartment syndrome; none experienced renal failure. Illnesses started 1 to 3 days after the triceps exercise. Forty players (93%) completed questionnaires. Among 19 players receiving at least 1 vote from a teammate as 1 of the 3 hardest working players, 13 (68%) experienced rhabdomyolysis versus 7 (33%) of 21 not considered hardest working (relative risk, 2.1; 95% confidence interval, 1.04-4.0). Of 40 players, 10 (25%) reported creatine supplement use, which was not associated with rhabdomyolysis. No player acknowledged use of alcohol, illicit drugs, or performance-enhancing drugs; results of performance-enhancing drug tests on the 4 players tested were negative. Environmental investigation did not identify additional factors contributing to illness.Conclusions:The upper arm exercise, possibly exacerbated by heat, led to rhabdomyolysis and compartment syndrome. Greater awareness of specific exercise hazards and prevention strategies can minimize risk for clinically significant muscle injury.