Dale R. Burwen

Guillain-Barré syndrome and Fisher syndrome: case definitions and guidelines for collection, analysis, and presentation of immunization safety data.

ames J. Sejvara,∗, Katrin S. Kohla, Jane Gidudua, Anthony Amatob, Nandini Bakshic, Roger Baxterc, ale R. Burwend, David R. Cornblathe, Jan Cleerbout f, Kathryn M. Edwardsg, Ulrich Heiningerh, ichard Hughes i, Najwa Khuri-Bulos j, Rudolf Korinthenbergk, Barbara J. Lawl, Ursula Munrom, elena C. Maltezoun, Patricia Nello,1, James Oleskep, Robert Sparksq, Priscilla Velentgasr, atricia Vermeers, Max Wiznitzer t, The Brighton Collaboration GBS Working Group2

Safety of trivalent inactivated influenza vaccines in adults: Background for pandemic influenza vaccine safety monitoring

In preparation for pandemic vaccine safety monitoring, we assessed adverse events reported to the Vaccine Adverse Event Reporting System following receipt of trivalent inactivated influenza vaccines among adults from 1990 through 2005. We calculated reporting rates for nonserious, serious, and neurological adverse events. We reviewed reports of recurrent events and deaths, as well as reports identified through advanced signal detection. The most frequently reported events were local reactions and systemic symptoms. Guillain-Barré syndrome was the most frequently reported serious event (0.70 reports per million vaccinations). Adverse event reporting rates have been reasonably constant over time. No new safety concerns emerged after our review of 15 years of post-licensure surveillance data. These findings provide useful information if pandemic vaccine is rapidly distributed and pre-licensure data are limited.

Association between Guillain-Barré syndrome and influenza A (H1N1) 2009 monovalent inactivated vaccines in the USA: a meta-analysis

BACKGROUND The influenza A (H1N1) 2009 monovalent vaccination programme was the largest mass vaccination initiative in recent US history. Commensurate with the size and scope of the vaccination programme, a project to monitor vaccine adverse events was undertaken, the most comprehensive safety surveillance agenda in the USA to date. The adverse event monitoring project identified an increased risk of Guillain-Barré syndrome after vaccination; however, some individual variability in results was noted. Guillain-Barré syndrome is a rare but serious health disorder in which a persons own immune system damages their nerve cells, causing muscle weakness, sometimes paralysis, and infrequently death. We did a meta-analysis of data from the adverse event monitoring project to ascertain whether influenza A (H1N1) 2009 monovalent inactivated vaccines used in the USA increased the risk of Guillain-Barré syndrome. METHODS Data were obtained from six adverse event monitoring systems. About 23 million vaccinated people were included in the analysis. The primary analysis entailed calculation of incidence rate ratios and attributable risks of excess cases of Guillain-Barré syndrome per million vaccinations. We used a self-controlled risk-interval design. FINDINGS Influenza A (H1N1) 2009 monovalent inactivated vaccines were associated with a small increased risk of Guillain-Barré syndrome (incidence rate ratio 2·35, 95% CI 1·42-4·01, p=0·0003). This finding translated to about 1·6 excess cases of Guillain-Barré syndrome per million people vaccinated. INTERPRETATION The modest risk of Guillain-Barré syndrome attributed to vaccination is consistent with previous estimates of the disorder after seasonal influenza vaccination. A risk of this small magnitude would be difficult to capture during routine seasonal influenza vaccine programmes, which have extensive, but comparatively less, safety monitoring. In view of the morbidity and mortality caused by 2009 H1N1 influenza and the effectiveness of the vaccine, clinicians, policy makers, and those eligible for vaccination should be assured that the benefits of inactivated pandemic vaccines greatly outweigh the risks. FUNDING US Federal Government.

Extensive Limb Swelling after Immunization: Reports to the Vaccine Adverse Event Reporting System

Extensive limb swelling (ELS) has been reported after vaccination with a limited number of vaccine types. We sought to describe vaccine types involved in and the clinical characteristics of ELS cases reported to the Vaccine Adverse Event Reporting System (VAERS). A case of ELS was defined as any report of edema extending at least to the elbow or knee of a vaccinated extremity. Four hundred ninety-seven cases were identified, with some describing swelling from the shoulder to the hand or the hip to the foot. Patient age ranged from 0.1 to 91 years. The proportion of reports of ELS associated with a given vaccine, among all VAERS reports received for that vaccine, varied substantially among vaccines. Most reactions began within 1 day after vaccination and involved other signs of inflammation. Postvaccination ELS can involve both the proximal and distal segments of the extremity, affects all age groups, and occurs after vaccination with a broad range of vaccines.

Effects of Stratification on Data Mining in the US Vaccine Adverse Event Reporting System (VAERS)

AbstractBackground: Vaccines are administered differentially according to age and sex, and disease patterns also vary among people of different age and sex groups. Estimates of disproportionality should be calculated based on comparisons of groups that have a similar likelihood of receiving similar vaccines and experiencing similar adverse events, to prevent false disproportionality from occurring. Stratified empirical Bayesian (EB) methods have been compared with crude, but not stratified, proportional reporting ratios (PRRs) in their performance on adverse event data. Objectives: (i) to implement stratification of PRR; (ii) to quantify and compare vaccine-event pairs that are highlighted by PRR and EB05 (the lower bound of the 90% CI of the EB geometric mean), for both crude and stratified; and (iii) to evaluate the effects of stratification by age and sex, in identifying adverse events that are accepted to be caused by vaccines. Methods: We applied EB and PRR data mining methods to data from the US Vaccine Adverse Event Reporting System (VAERS). We stratified PRR and EB05 by age and sex. To study the effects of stratification, we compared the crude PRR and stratified PRR. We also assessed the crude EB05 and stratified EB05, and then compared the effects of stratification on EB05 and PRR. Results: Stratification not only changed the number of vaccine-event pairs that were highlighted, but also changed which pairs were highlighted. There were 283 vaccine-event pairs that were highlighted by the crude EB05, but not the stratified; 12 that were highlighted by the stratified EB05, but not the crude; and 162 that were highlighted by both. Similarly, there were 701 vaccine-event pairs that were highlighted by the crude PRR, but not the stratified; 139 that were highlighted by the stratified PRR, but not the crude; and 895 that were highlighted by both. There were 1466 vaccine-event pairs in which the effect of stratification was different for EB05 and PRR. Conclusion: To our knowledge, this is the first published analysis using stratified PRRs. In this analysis of passive surveillance data, stratification revealed and reduced confounding in EB and PRR, and also unmasked some vaccine-event pairs that the crude values did not highlight. Stratification should be applied if confounding is suspected. By decreasing the total number of highlighted vaccine-event pairs, stratification is likely to increase efficiency and therefore might reduce workload.

Evaluation of Guillain-Barré Syndrome Among Recipients of Influenza Vaccine in 2000 and 2001

BACKGROUND The 1976-1977 swine influenza vaccine was associated with an elevated risk of Guillain-Barré Syndrome (GBS), especially within 6 weeks after vaccination. A 2004 IOM report concluded that evidence was inadequate to accept or reject a causal relationship between subsequent influenza vaccine formulations and GBS. Studies published after the IOM report have been limited by passively reported data or lack of validation of coded diagnoses. PURPOSE To evaluate whether influenza vaccine is associated with GBS. METHODS Controlled observational study using national data from the Medicare program, which ensures a predominantly elderly population. People included had a Medicare claim for influenza vaccination during September-December in 2000 or 2001. Medical records were reviewed to classify definite, probable, or possible GBS (or not a case) using a standardized case definition. In a risk interval design, the incidence rate of GBS during Weeks 0-6 after vaccination (exposed period) was compared to Weeks 9-14 after vaccination (comparison period). Data collection occurred during 2003-2007, and analysis was conducted during 2007-2009. RESULTS Primary analysis included 22.2 million vaccinees, among whom 164 definite or probable GBS cases with onset during Weeks 0-6 or 9-14 were identified. The incidence rate ratio (IRR [95% CIs]) based on the GBS rate in the vaccine-exposed versus comparison periods, was 1.04 (0.76, 1.43) for combined years; 0.86 (0.52, 1.41) among people vaccinated in 2000; and 1.21 (0.79, 1.86) among people vaccinated in 2001. Secondary analysis additionally included 74 possible GBS cases; results were similar. CONCLUSIONS Overall, the results do not support an association between influenza vaccine receipt and GBS among the elderly for the years studied (2000-2001 and 2001-2002 formulations).

Blood use by inpatient elderly population in the United States

BACKGROUND: Our objective was to characterize inpatient blood use by the US elderly population during 2001. As the US population ages the demand for blood is expected to grow. There have been no comprehensive studies, however, detailing blood use by the elderly in the United States.

Surveillance for Guillain–Barré Syndrome After Influenza Vaccination Among the Medicare Population, 2009–2010

OBJECTIVES We implemented active surveillance for Guillain-Barré syndrome (GBS) following seasonal or H1N1 influenza vaccination among the Medicare population during the 2009-2010 influenza season. METHODS We used weekly Medicare claims data to monitor vaccinations and subsequent hospitalizations with principal diagnosis code for GBS within 42 days. Group sequential testing assessed whether the observed GBS rate exceeded a critical limit based on the expected rate from 5 previous years adjusted for claims delay. We evaluated the lag between date of service and date of claims availability and used it for adjustment. RESULTS By July 30, 2010 (after 26 interim surveillance tests), 14.0 million seasonal and 3.3 million H1N1 vaccinations had accrued. Taking into account claims delay appropriately lowered the critical limit during early monitoring. The observed GBS rate was below the critical limit throughout the surveillance. CONCLUSIONS Medicare data contributed rapid safety monitoring among millions of 2009-2010 influenza vaccine recipients. Adjustment for claims delay facilitates early detection of potential safety issues. Although limited by lack of medical record review to confirm cases, this claims-based surveillance did not indicate a statistically significant elevated GBS rate following seasonal or H1N1 influenza vaccination.

Adverse events after anthrax vaccination reported to the Vaccine Adverse Event Reporting System (VAERS), 1990-2007.

During the period March 1, 1998 to January 14, 2007, approximately 6 million doses of Anthrax vaccine adsorbed (AVA) vaccine were administered. As of January 16, 2007, 4753 reports of adverse events following receipt of AVA vaccination had been submitted to the Vaccine Adverse Event Reporting System (VAERS). Taken together, reports to VAERS did not definitively link any serious unexpected risk to this vaccine, and review of death and serious reports did not show a distinctive pattern indicative of a causal relationship to AVA vaccination. Continued monitoring of VAERS and analysis of potential associations between AVA vaccination and rare, serious events is warranted.

Chart-Confirmed Guillain-Barré Syndrome After 2009 H1N1 Influenza Vaccination Among the Medicare Population, 2009–2010

Given the increased risk of Guillain-Barré Syndrome (GBS) found with the 1976 swine influenza vaccine, both active surveillance and end-of-season analyses on chart-confirmed cases were performed across multiple US vaccine safety monitoring systems, including the Medicare system, to evaluate the association of GBS after 2009 monovalent H1N1 influenza vaccination. Medically reviewed cases consisted of H1N1-vaccinated Medicare beneficiaries who were hospitalized for GBS. These cases were then classified by using Brighton Collaboration diagnostic criteria. Thirty-one persons had Brighton level 1, 2, or 3 GBS or Fisher Syndrome, with symptom onset 1-119 days after vaccination. Self-controlled risk interval analyses estimated GBS risk within the 6-week period immediately following H1N1 vaccination compared with a later control period, with additional adjustment for seasonality. Our results showed an elevated risk of GBS with 2009 monovalent H1N1 vaccination (incidence rate ratio = 2.41, 95% confidence interval: 1.14, 5.11; attributable risk = 2.84 per million doses administered, 95% confidence interval: 0.21, 5.48). This observed risk was slightly higher than that seen with previous seasonal influenza vaccines; however, additional results that used a stricter case definition (Brighton level 1 or 2) were not statistically significant, and our ability to account for preceding respiratory/gastrointestinal illness was limited. Furthermore, the observed risk was substantially lower than that seen with the 1976 swine influenza vaccine.