N 1999, THE RHESUS TETRAVALENT rotavirus vaccine (RRV, Rotashield, Wyeth) was withdrawn from the US market due to a significantly increased risk of intussusception following vaccination. The largest increased risk (Ͼ30-fold) of intussusception was observed during the 3 to 7 days following the first dose of the vaccine. [1][2][3] Since then, 2 vaccines to prevent rotavirus infection have been licensed for use in the United States: a pentavalent rotavirus vaccine (RV5, RotaTeq, Merck) in 2006 and a monovalent rotavirus vaccine (RV1, Rotarix, GlaxoSmithKline Biologicals) in 2008. 4,5 The pentavalent rotavirus vaccine is a 3-dose series that, according to the Advisory Committee on Immunization Practices, should be given at ages 2, 4, and 6 months; RV1 is a 2-dose series to be

Background/Aim: We describe the incidence of Guillain-Barré syndrome (GBS) in a large United States cohort. Methods: Between 2000 and 2009, we identified visits with an ICD-9 code for GBS (357.0) from all persons with continuous enrollment for at least 1 year. The primary case definition was restricted to emergency department and inpatient visits. We calculated age-standardized rates and used multivariate Poisson regression to assess variation in rates by sex, age, season and year of diagnosis. We tabulated descriptive characteristics and the positive predictive value (PPV) for a subset of the visits with available medical record review. Results: 1,619 visits with the GBS ICD-9 code were identified from 50,290,898 person-years of observation. After considering the PPV (55%) for record-reviewed visits, the age-standardized incidence rate was approximately 1.72/100,000 person-years. The rate was 40% higher for males and increased by 50% for every 10-year increase in age. The rate was 15% higher in winter and spring compared with summer. Rates were higher in more recent years. Conclusions: GBS rates are higher in males and increase considerably with age. The potential reasons for differences in rates by season and the increased rates in more recent years should be further investigated.

The Post-Licensure Rapid Immunization Safety Monitoring (PRISM) system is a cohort-based active surveillance network initiated by the US Department of Health and Human Services to supplement preexisting and other vaccine safety monitoring systems in tracking the safety of monovalent pandemic 2009 H1N1 influenza vaccine in the United States during 2009-2010. PRISM investigators conducted retrospective analysis to determine whether 2009 H1N1 vaccination was associated with increased risk of any of 14 prespecified outcomes. Five health insurance and associated companies with 38 million members and 9 state/city immunization registries contributed records on more than 2.6 million doses of 2009 H1N1 vaccine. Data on outcomes came from insurance claims. Complementary designs (self-controlled risk interval, case-centered, and current-vs.-historical comparison) were used to optimize control for confounding and statistical power. The self-controlled risk interval analysis of chart-confirmed Guillain-Barré syndrome found an elevated but not statistically significant incidence rate ratio following receipt of inactivated 2009 H1N1 vaccine (incidence rate ratio = 2.50, 95% confidence interval: 0.42, 15.0) and no cases following live attenuated 2009 H1N1 vaccine. The study did not control for infection prior to Guillain-Barré syndrome, which may have been a confounder. The risks of other health outcomes of interest were generally not significantly elevated after 2009 H1N1 vaccination.

An increased risk of Guillain-Barré syndrome (GBS) following administration of the 1976 swine influenza vaccine led to a heightened focus on GBS when monovalent vaccines against a novel influenza A (H1N1) virus of swine origin were introduced in 2009. GBS cases following receipt of monovalent inactivated (MIV) and seasonal trivalent inactivated (TIV) influenza vaccines in the Vaccine Safety Datalink Project in 2009-2010 were identified in electronic data and confirmed by medical record review. Within 1-42 days following vaccination, 9 cases were confirmed in MIV recipients (1.48 million doses), and 8 cases were confirmed in TIV-only recipients who did not also receive MIV during 2009-2010 (1.72 million doses). Five cases following MIV and 1 case following TIV-only had an antecedent respiratory infection, a known GBS risk factor; furthermore, unlike TIV, MIV administration was concurrent with heightened influenza activity. In a self-controlled risk interval analysis comparing GBS onset within 1-42 days following MIV with GBS onset 43-127 days following MIV, the risk difference was 5.0 cases per million doses (95% confidence interval: 0.5, 9.5). No statistically significant increased GBS risk was found within 1-42 days following TIV-only vaccination versus 43-84 days following vaccination (risk difference = 1.1 cases per million doses, 95% confidence interval: -3.1, 5.4). Further evaluation to assess GBS risk following both vaccination and respiratory infection is warranted.

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