Guillain-Barré syndrome after exposure to influenza virus

Recent developments and future directions in Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) encompasses a spectrum of acquired neuropathic conditions characterized by inflammatory demyelinating or axonal peripheral neuropathy with acute onset. Clinical and experimental studies in the past years have led to substantial progress in epidemiology, pathogenesis of GBS variants, and identification of prognostic factors relevant to treatment. In this review we provide an overview and critical assessment of the most recent developments and future directions in GBS research.

Guillain-Barre syndrome following quadrivalent human papillomavirus vaccination among vaccine-eligible individuals in the United States

Post-marketing surveillance studies provide conflicting evidence about whether Guillain-Barre syndrome occurs more frequently following quadrivalent human papillomavirus (HPV4) vaccination. We aimed to assess whether Guillain-Barre syndrome is reported more frequently following HPV4 vaccination than other vaccinations among females and males aged 9 to 26 y in the United States. We used adverse event reports received by the United States Vaccine Adverse Event Reporting System (VAERS) between January 1, 2010 and December 31, 2012 to estimate overall, age-, and sex-specific proportional reporting ratios (PRRs) and corresponding Χ2 values for reports of Guillain-Barre syndrome between 5 and 42 d following HPV vaccination. Minimum criteria for a signal using this approach are 3 or more cases, PRR≥2, and Χ2≥4. Guillain-Barre syndrome was listed as an adverse event in 45 of 14,822 reports, of which 9 reports followed HPV4 vaccination and 36 reports followed all other vaccines. The overall, age-, and sex-specific PRR estimates were uniformly below 1. In addition, the overall, age-, and sex-specific Χ2 values were uniformly below 3. Our analysis of post-marketing surveillance data does not suggest that Guillain-Barre syndrome is reported more frequently following HPV4 vaccination than other vaccinations among vaccine-eligible females or males in the United States. Our findings may be useful when discussing the risks and benefits of HPV4 vaccination.

Acute hepatitis E complicated by Guillain-Barre syndrome in Portugal, December 2012--a case report

Autochthonous hepatitis E virus (HEV) infection has been increasingly reported in Europe and the United States, mostly arising from genotype 3 and less frequently genotype 4. We report here on a patient with HEV genotype 3a infection complicated by Guillain-Barré syndrome in Portugal in December 2012. We draw attention to the diagnosis of autochthonous HEV infection and to its rare, but important, neurological complications.

Guillain-Barré Syndrome, Influenza Vaccination, and Antecedent Respiratory and Gastrointestinal Infections: A Case-Centered Analysis in the Vaccine Safety Datalink, 2009-2011

BACKGROUND

Guillain-Barré Syndrome (GBS) can be triggered by gastrointestinal or respiratory infections, including influenza. During the 2009 influenza A (H1N1) pandemic in the United States, monovalent inactivated influenza vaccine (MIV) availability coincided with high rates of wildtype influenza infections. Several prior studies suggested an elevated GBS risk following MIV, but adjustment for antecedent infection was limited.

METHODS

We identified patients enrolled in health plans participating in the Vaccine Safety Datalink and diagnosed with GBS from July 2009 through June 2011. Medical records of GBS cases with 2009-10 MIV, 2010-11 trivalent inactivated influenza vaccine (TIV), and/or a medically-attended respiratory or gastrointestinal infection in the 1 through 141 days prior to GBS diagnosis were reviewed and classified according to Brighton Collaboration criteria for diagnostic certainty. Using a case-centered design, logistic regression models adjusted for patient-level time-varying sources of confounding, including seasonal vaccinations and infections in GBS cases and population-level controls.

RESULTS

Eighteen confirmed GBS cases received vaccination in the 6 weeks preceding onset, among 1.27 million 2009-10 MIV recipients and 2.80 million 2010-11 TIV recipients. Forty-four confirmed GBS cases had infection in the 6 weeks preceding onset, among 3.77 million patients diagnosed with medically-attended infection. The observed-versus-expected odds that 2009-10 MIV/2010-11 TIV was received in the 6 weeks preceding GBS onset was odds ratio = 1.54, 95% confidence interval (CI), 0.59-3.99; risk difference = 0.93 per million doses, 95% CI, -0.71-5.16. The association between GBS and medically-attended infection was: odds ratio = 7.73, 95% CI, 3.60-16.61; risk difference = 11.62 per million infected patients, 95% CI, 4.49-26.94. These findings were consistent in sensitivity analyses using alternative infection definitions and risk intervals for prior vaccination shorter than 6 weeks.

CONCLUSIONS

After adjusting for antecedent infections, we found no evidence for an elevated GBS risk following 2009-10 MIV/2010-11 TIV influenza vaccines. However, the association between GBS and antecedent infection was strongly elevated.

Orthopaedic manifestations and diagnostic clues in children with Guillain-Barré syndrome

INTRODUCTION

Guillain-Barré syndrome (GBS) is an acute inflammatory demyelinating polyneuropathy characterized by symmetric limb weakness. Children with GBS sometimes consult the orthopaedists because of limb pain and gait disturbance. The orthopaedists, however, are unfamiliar with GBS, since it has rarely been delineated in detail in the orthopaedic literature. In the present study, we specifically describe orthopaedic manifestations and diagnostic clues in pediatric GBS.

METHODS

We reviewed seven patients with pediatric GBS in regard to age, gender, clinical symptoms, department at the first medical consultation, initial diagnosis, physical and laboratory findings, medical interventions, and the latest clinical outcome.

RESULTS

There were five boys and two girls, with a mean age at presentation of 7.2 years. Gait disturbance associated with lower limb pain and weakness was the most frequent early clinical symptom. Among the five patients who presented initially at the orthopaedic department, three were misdiagnosed. Loss of deep tendon reflexes was seen in all patients. Anti-ganglioside antibodies were positive in three and protein levels of cerebrospinal fluid were elevated in five patients. Six patients recovered completely after intravenous immunoglobulin (IVIG) treatment, while one patient who had not undergone IVIG treatment showed minor residual disability.

CONCLUSIONS

Acute symmetrical limb pain and gait disturbance associated with loss of tendon reflexes were important clinical manifestations of pediatric GBS. Early diagnosis is essential to prevent delayed recovery, long-term weakness, and permanent functional disabilities.

Lack of association of Guillain-Barré syndrome with vaccinations

BACKGROUND

Guillain-Barré syndrome (GBS) is an acute polyradiculoneuropathy, thought to be an autoimmune process. Although cases of GBS have been reported following a wide range of vaccines, a clear association has only been established with the 1976 H1N1 inactivated influenza vaccine.

METHODS

We identified hospitalized GBS cases from Kaiser Permanente Northern California (KPNC) from 1995 through 2006. The medical record of each suspected case was neurologist-reviewed according to the Brighton Collaboration GBS case definition; only confirmed cases were included in the analyses, and cases of Miller Fisher syndrome were excluded. Using a case-centered design, we compared the odds of vaccination in the 6 and 10 weeks prior to onset of GBS to the odds of vaccination during the same time intervals in all vaccinated individuals in the entire KPNC population.

RESULTS

We confirmed 415 incident cases of GBS (including Brighton levels 1, 2, and 3) during the study period (>30 million person-years). Incidence peaked during the winter months. The odds ratio of influenza vaccination within a 6-week interval prior to GBS, compared with the prior 9 months, was 1.1 (95% confidence interval [CI], .4-3.1). The risk in the 6-week interval compared to the prior 12 months for tetanus diphtheria combination, 23-valent pneumococcal polysaccharide, and for all vaccines combined was 1.4 (95% CI, .3-4.5), 0.7 (95% CI, .1-2.9), and 1.3 (95% CI, .8-2.3), respectively.

CONCLUSIONS

In this large retrospective study, we did not find evidence of an increased risk of GBS following vaccinations of any kind, including influenza vaccination.

[Guillain-Barré syndrome after exposure to influenza]

Guillain-Barré Syndrome (GBS) is an acquired, monophasic inflammatory polyradiculoneuritis of autoimmune origin, which occurs after infection and occasionally also after vaccination. Seasonal and pandemic influenza vaccines have in particular been implicated as triggers for GBS. However, a number of recent studies indicate that infection with influenza virus may also cause GBS. This review summarizes the epidemiological and experimental data of the association of GBS with exposure to influenza antigens by immunization (including vaccines against A/H1N1/2009) and infection. Vaccination against influenza is associated with a very low risk for the occurrence of GBS. In contrast infection with influenza may play a more important role as a triggering factor for GBS than previously assumed.

Safety of influenza vaccines

PURPOSE OF REVIEW

To review recent publications on the safety of influenza vaccines [both the injectable, inactivated trivalent influenza vaccine (TIV) and the intranasal, live attenuated influenza vaccine (LAIV)] and new recommendations regarding their use.

RECENT FINDINGS

Numerous studies have demonstrated that TIV can be safely administered to patients with egg allergy. Influenza vaccines are very unlikely to cause or exacerbate Guillain-Barré syndrome (GBS). TIV cannot cause asthma exacerbations, whereas there may be some slight risk that LAIV could do so. TIV is well tolerated by patients with immunocompromise. Some brands of influenza vaccine are not indicated for certain age groups due to lack of effectiveness or possible side effects.

SUMMARY

TIV should be administered to patients with egg allergy with appropriate precautions. Influenza vaccines should be withheld from patients with a history of GBS only if the GBS began within 6 weeks of prior influenza immunization. TIV should be given to patients with asthma, but they should not receive LAIV. TIV should be given to immunocompromised patients, but they should not receive LAIV. Contacts of most immunocompromised patients can receive either TIV or LAIV. Age appropriate brands of influenza vaccine should be used.

Simultaneous measurements of auto-immune and infectious disease specific antibodies using a high throughput multiplexing tool

Considering importance of ganglioside antibodies as biomarkers in various immune-mediated neuropathies and neurological disorders, we developed a high throughput multiplexing tool for the assessment of gangliosides-specific antibodies based on Biolpex/Luminex platform. In this report, we demonstrate that the ganglioside high throughput multiplexing tool is robust, highly specific and demonstrating ∼100-fold higher concentration sensitivity for IgG detection than ELISA. In addition to the ganglioside-coated array, the high throughput multiplexing tool contains beads coated with influenza hemagglutinins derived from H1N1 A/Brisbane/59/07 and H1N1 A/California/07/09 strains. Influenza beads provided an added advantage of simultaneous detection of ganglioside- and influenza-specific antibodies, a capacity important for the assay of both infectious antigen-specific and autoimmune antibodies following vaccination or disease. Taken together, these results support the potential adoption of the ganglioside high throughput multiplexing tool for measuring ganglioside antibodies in various neuropathic and neurological disorders.

Neurologic complications of influenza

Neurologic complications associated with influenza infection represent rare, but often underappreciated, manifestations of both seasonal and global pandemic influenza. Seizures are the most common neurologic complication, occurring as febrile seizures, as exacerbations in patients with epilepsy, or as symptoms of other influenza-induced neurologic disorders. Encephalopathy is the second most common neurologic complication associated with influenza. A wide spectrum of conditions ranging from coma with severe long-term morbidity or mortality and more mild altered mental states that resolve with minimal-to-no sequelae have been reported. Other less common neurologic complications that have been described include stroke, focal neurologic deficits, Guillain-Barré syndrome, acute disseminated encephalomyelitis, and transverse myelitis.

Influenza H1N1 (swine flu) vaccination: a safety surveillance feasibility study using self-reporting of serious adverse events and pregnancy outcomes

AIMS

During the global H1N1 influenza A (swine flu) pandemic 2009–2010, swine flu vaccines were expeditiously licensed and a mass vaccination programme for high risk groups, including pregnant women, was introduced in the UK. This pilot active safety surveillance study was performed to establish the feasibility of rapidly monitoring the new swine flu vaccines in large patient numbers receiving or offered the vaccination under normal conditions of use within a short time frame.

METHODS

A cohort design with safety data capture through modern technologies was carried out in Scotland, UK during the winter swine flu vaccination programme 2009–2010 in individuals receiving or offered the swine flu vaccination. The main outcome measures were self-reported serious adverse events (SAEs) and pregnancy outcomes.

RESULTS

The cohort comprised 4066 people; 3754 vaccinated and 312 offered the vaccination but not vaccinated. There were 939 self-reported events (838 different events), 53 judged to fit SAE criteria by the investigators, with nine judged as possibly, probably or definitely vaccine related. None of the seven deaths (six in vaccinees) were judged as vaccine related. One hundred and twenty-eight women reported 130 pregnancies during the study with 117 pregnant at study start. There were reports of four miscarriages in three women and six possible congenital abnormalities in live births.

CONCLUSIONS

Overall, no significant safety issues were identified. The methodology and use of modern technologies to collect safety data from large numbers of patients was successful and could be used again in similar safety studies.

Invited commentary: Influenza vaccine and Guillain-Barre syndrome--is there a risk?

After a new reassortant swine influenza A H1N1 virus caused outbreaks in Mexico and the United States in 2009, a vaccine was prepared from this virus to immunize the entire US population. Surveillance for Guillain-Barré syndrome (GBS) after receipt of this vaccine was carried out in 3 populations: the Vaccine Safety Datalink Project, the 10 Centers for Disease Control and Prevention Emerging Infections Program sites, and a network of large insurance companies. These studies found a small increase of approximately 1 case of GBS per million vaccinees above the baseline rate, which is similar to that observed after administration of seasonal influenza vaccines over the past several years. Enhanced surveillance for GBS was conducted in 2009-2010 because of the experience in 1976 of 362 GBS cases' occurring during the 6 weeks after influenza vaccination of 45 million persons, an 8.8-fold increase over background rates. The 1976 mass immunization had been conducted to prevent an influenza epidemic from another swine influenza A H1N1 recombinant virus. It can be concluded from these recent studies that influenza vaccination overall is of public health benefit, helping to reduce mortality and prevent the thousands of deaths that occur from annual seasonal influenza outbreaks, despite the possibility of a small increased risk of GBS associated with influenza vaccines.

Declining Guillain-Barré syndrome after campylobacteriosis control, New Zealand, 1988-2010

Food safety measures that lower incidence of campylobacteriosis might also prevent Guillain-Barré syndrome.

A 3-month-old baby with H1N1 and Guillain-Barré syndrome

Majority of children with pandemic influenza A (H1N1)pdm09 experience mild illness with full recovery without treatment. A previously healthy two and a half month-old girl was admitted to our paediatric intensive care unit because of severe respiratory failure with A (H1N1)pdm09 infection. Despite initial clinical improvement all attempts to extubate to non-invasive ventilation were unsuccessful and 2 to 3 weeks after symptom onset she started periods of cardiovascular instability and a progressive neurological deterioration with distal symmetrical progressive motor weakness and areflexia. All investigations were normal except elevated liver enzymes and cerebrospinal fluid examination that revealed elevated protein without pleocytosis. A possible diagnosis of Guillain-Barré syndrome (GBS) was considered and electromyogram was compatible with axonal form of GBS. To our knowledge this is the youngest case of GBS acquired postnatally and the first in children associated with H1N1 virus.

Anti-ganglioside antibodies were not detected in human subjects infected with or vaccinated against 2009 pandemic influenza A (H1N1) virus

Recipients of influenza A (H1N1) vaccine in 1976 had an increased risk for the neurologic disorder Guillain-Barré syndrome (GBS). Anti-ganglioside antibodies, which might be associated with the development of GBS, were previously reported to be induced in mice immunized with an H1N1 vaccine of 1976 or another influenza vaccine. In this study we analyzed anti-ganglioside antibodies in human subjects infected with or vaccinated against 2009 pandemic H1N1, including eight patients diagnosed to have post-vaccination GBS. Antibodies against GM1 or another ganglioside were not detected in any subject or in vaccinated mice. Our results did not support the induction of anti-ganglioside antibodies by influenza viruses or vaccines.

The ins and outs of universal childhood influenza vaccination

Influenza viruses continue to cause disease of varying severity among humans. People with underlying disease and the elderly are at increased risk of developing severe disease after infection with an influenza virus. As effective and safe vaccines are available, the WHO has recommended vaccinating these groups against influenza annually. In addition to this recommendation, public health authorities of a number of countries have recently recommended vaccinating all healthy children aged 6-59 months against influenza. Here, we review the currently available data concerning the burden of disease in children, the economical impact of implementing universal vaccination of children, the efficacy of currently available influenza virus vaccines, the theoretical concerns regarding preventing immunity otherwise induced by infections with seasonal influenza viruses, and finally, how to address these concerns.

An incremental economic evaluation of targeted and universal influenza vaccination in pregnant women

OBJECTIVE

Pregnancy is associated with increased influenza hospitalizations and physician visits (events) in healthy women and those with co-morbidities. Annual influenza immunization is recommended for all pregnant women. Although vaccination is expected to reduce influenza-related events, the economic implications are unclear. We developed an economic model to estimate the cost-effectiveness (CE) of different vaccination strategies in Nova Scotia.

METHODS

A decision tree characterized the one-year costs and consequences of targeted (pregnant women with co-morbidities only) and universal (all pregnant women) vaccination strategies relative to a no-vaccination strategy. Baseline event probabilities, vaccine effectiveness, costs and quality-of-life weights were derived from individual-level Nova Scotia administrative databases, health system sources and published reports. Sensitivity analyses tested the impact of varying key parameters, including vaccine effectiveness and mode of delivery.

RESULTS

Targeted vaccination was cost-saving relative to no vaccination when delivered by public health clinics (PHC) or routine family practitioner (FP) visit. Cost per quality-adjusted life year gained by universal vaccination relative to targeted strategy was < $40,000 when delivered by PHC or routine FP visit. Net cost of universal vaccination by PHC or a routine FP visit was < $10 per pregnant woman.

CONCLUSION

Universal vaccination of pregnant women appears cost-effective when delivered by PHC or as part of a routine FP prenatal visit. Targeted vaccination of pregnant women with co-morbidities can be cost-saving, but the possibility of higher vaccine uptake with a universal compared to a targeted strategy must be considered in addition to costs in program planning.

Miller Fisher syndrome associated with influenza A infection

A 36-year-old, previously healthy man presented with Miller Fisher syndrome (MFS) five days after he was diagnosed with an influenza A infection by a rapid antigen test. He had not received any recent vaccinations. He had no loss of consciousness. Bilateral ophthalmoplegia, blepharoptosis, areflexia, and ataxic gait were noted. One week after treatment with intravenous immunoglobulin, his ophthalmoplegia, blepharoptosis, and ataxic gait had gradually improved, and his deep tendon reflexes returned. Anti-GQ1b IgG antibodies were detected in his serum. There has been no previous report of postinfectious MFS following confirmed an influenza A infection in an adult.

Síndrome de Guillain-Barré em associação temporal com a vacina influenza A

OBJETIVO: Descrever um caso de síndrome de Guillain-Barré em associação temporal com a vacina influenza A (H1N1) 2009. DESCRIÇAO DO CASO: Menino de quatro anos com queixa inicial de dor em coxa direita e perda de força muscular ascendente 15 dias após a segunda dose da vacina influenza A (H1N1) 2009. Ao exame neurológico apresentava tetraparesia e arreflexia, com predomínio em membros inferiores. A eletroneuromiografia evidenciou redução da velocidade e bloqueio de condução neuronal, com discreta perda axonal secundária. Foi tratado com imunoglobulina por via intravenosa, atingiu platô no quarto dia de evolução da doença e, depois, houve melhora progressiva da força muscular. COMENTÁRIOS: Com o emprego em larga escala da vacina influenza A (H1N1) 2009 em nosso meio e os dados preliminares do sistema de vigilância norte-americano mostrando associação temporal significante com a síndrome de Guillain-Barré, recomenda-se a descrição dos casos suspeitos dessa associação. A vacina continua sendo o método mais efetivo para prevenir doença grave e morte por influenza.

Events temporarily associated with anti-influenza A (H1N1) vaccination in Mexico

BACKGROUND AND AIMS

In Mexico from December 2009 to June 2010, 45,490,501 doses of the vaccine against the influenza virus were administered; 27,048,330 of those corresponded to influenza A (H1N1) and 18,442,171 to seasonal influenza. Therefore, the assessment of events temporarily associated with vaccination (ETAV) is mandatory.

METHODS

The database corresponding to the ETAV associated with influenza (A [H1N1] and seasonal) immunization reported between December 2009 and June 2010 was analyzed. Patients who displayed at least one ETAV with one of the following schedules were included: A) influenza A (H1N1) vaccine, B) seasonal influenza vaccine, C) influenza A (H1N1) vaccine and seasonal influenza vaccine.

RESULTS

A total of 597 ETAVs were reported. The 20- to 49-year-old age group was the most affected one (52.9%). The ETAV notification rate for influenza A (H1N1) vaccination was 1.41/100,000 applied doses vs. 0.74/100,000 applied doses corresponding to the seasonal influenza vaccination. Fifty seven events were considered serious (14 corresponded to Guillain-Barré syndrome) and these were considered coincidental unrelated events.

CONCLUSIONS

There is no evidence of an increased rate of Guillain-Barré Syndrome with respect to the cases expected in the general population.

Guillain-Barré syndrome associated with the D222E variant of the 2009 pandemic influenza A (H1N1) virus: case report and review of the literature

Guillain-Barré syndrome (GBS) is an acute immune-mediated disorder of the peripheral nervous system and a triggering infectious event is often reported in the weeks before the disease onset. Influenza viruses have been associated with Guillain-Barré syndrome (GBS), both after infection and, in rare cases, after vaccination. However, GBS has rarely reported to be a neurological complication of the recent pandemic influenza A(H1N1) 2009 virus infections. Here we describe the case of a young man, who developed acute severe motor inflammatory demyelinating polyradiculoneuropathy during influenza A(H1N1)2009 infection. Peculiar features are the findings of a mutated haemagglutinin gene (D222E variant), which has never previously been associated with neurological involvement, and the almost simultaneous appearance of respiratory infectious and immune-mediated neurological symptoms. Moreover we review the clinical presentation, laboratory findings and outcome of influenza-related GBS.

No evidence of a link between influenza vaccines and Guillain-Barre syndrome-associated antiganglioside antibodies

Please cite this paper as: Wang et al. (2011) No evidence of a link between influenza vaccines and Guillain–Barre syndrome–associated antiganglioside antibodies. Influenza and Other Respiratory Viruses 6(3), 159–166.

Background  Guillain–Barre syndrome (GBS) is a rare autoimmune disease characterized by acute, progressive peripheral neuropathy and is commonly associated with the presence of antiganglioside antibodies. Previously, influenza vaccination was linked with the increased incidence of GBS; however, whether antiganglioside antibodies are subsequently induced remains unresolved.

Methods  Sera from human subjects vaccinated with seasonal influenza vaccines from the 2007–2008, 2008–2009, or 1976–1977 influenza seasons were screened for the induction of immunity to influenza and the presence of antiganglioside antibodies pre‐ and post‐vaccination. Likewise, sera from mice vaccinated with seasonal influenza vaccines (1988–1989, 2007–2008) or “swine flu” pandemic vaccines (1976, 2009) were assessed in the same manner. Viruses were also screened for cross‐reacting ganglioside epitopes.

Results  Antiganglioside antibodies were found to recognize influenza viruses; this reactivity correlated with virus glycosylation. Antibodies to influenza viruses were detected in human and mouse sera, but the prevalence of antiganglioside antibodies was extremely low.

Conclusions  Although the correlation between antiganglioside antibody cross‐reactivity and glycosylation of viruses suggests the role of shared carbohydrate epitopes, no correlation was observed between hemagglutinin‐inhibition titers and the induction of antiganglioside antibodies after influenza vaccination.

Epidemic viral pneumonia and other emerging pathogens

Viruses cause a high percentage of community-acquired pneumonias. The advent of polymerase chain reaction and other molecular techniques has been associated with the detection of a higher prevalence of common respiratory viruses than previously suspected. Better diagnostics have shown new viral pathogens regularly in epidemics, immunocompromised patients, and occasionally children. Despite better diagnostics, treatment for all but influenza is still very limited.

Guillain-Barre syndrome and adjuvanted pandemic influenza A (H1N1) 2009 vaccine: multinational case-control study in Europe

OBJECTIVE

To assess the association between pandemic influenza A (H1N1) 2009 vaccine and Guillain-Barré syndrome.

DESIGN

Case-control study.

SETTING

Five European countries.

PARTICIPANTS

104 patients with Guillain-Barré syndrome and its variant Miller-Fisher syndrome matched to one or more controls. Case status was classified according to the Brighton Collaboration definition. Controls were matched to cases on age, sex, index date, and country.

MAIN OUTCOME MEASURES

Relative risk estimate for Guillain-Barré syndrome after pandemic influenza vaccine.

RESULTS

Case recruitment and vaccine coverage varied considerably between countries; the most common vaccines used were adjuvanted (Pandemrix and Focetria). The unadjusted pooled risk estimate for all countries was 2.8 (95% confidence interval 1.3 to 6.0). After adjustment for influenza-like illness/upper respiratory tract infection and seasonal influenza vaccination, receipt of pandemic influenza vaccine was not associated with an increased risk of Guillain-Barré syndrome (adjusted odds ratio 1.0, 0.3 to 2.7). The 95% confidence interval shows that the absolute effect of vaccination could range from one avoided case of Guillain-Barré syndrome up to three excess cases within six weeks after vaccination in one million people.

CONCLUSIONS

The risk of occurrence of Guillain-Barré syndrome is not increased after pandemic influenza vaccine, although the upper limit does not exclude a potential increase in risk up to 2.7-fold or three excess cases per one million vaccinated people. When assessing the association between pandemic influenza vaccines and Guillain-Barré syndrome it is important to account for the effects of influenza-like illness/upper respiratory tract infection, seasonal influenza vaccination, and calendar time.

Estimating background rates of Guillain-Barré Syndrome in Ontario in order to respond to safety concerns during pandemic H1N1/09 immunization campaign

BACKGROUND

The province of Ontario, Canada initiated mass immunization clinics with adjuvanted pandemic H1N1 influenza vaccine in October 2009. Due to the scale of the campaign, temporal associations with Guillain-Barré syndrome (GBS) and vaccination were expected. The objectives of this analysis were to estimate the number of background GBS cases expected to occur in the projected vaccinated population and to estimate the number of additional GBS cases which would be expected if an association with vaccination existed. The number of influenza-associated GBS cases was also determined.

METHODS

Baseline incidence rates of GBS were determined from published Canadian studies and applied to projected vaccine coverage data to estimate the expected number of GBS cases in the vaccinated population. Assuming an association with vaccine existed, the number of additional cases of GBS expected was determined by applying the rates observed during the 1976 Swine Flu and 1992/1994 seasonal influenza campaigns in the United States. The number of influenza-associated GBS cases expected to occur during the vaccination campaign was determined based on risk estimates of GBS after influenza infection and provincial influenza infection rates using a combination of laboratory-confirmed cases and data from a seroprevalence study.

RESULTS

The overall provincial vaccine coverage was estimated to be between 32% and 38%. Assuming 38% coverage, between 6 and 13 background cases of GBS were expected within this projected vaccinated cohort (assuming 32% coverage yielded between 5-11 background cases). An additional 6 or 42 cases would be expected if an association between GBS and influenza vaccine was observed (assuming 32% coverage yielded 5 or 35 additional cases); while up to 31 influenza-associated GBS cases could be expected to occur. In comparison, during the same period, only 7 cases of GBS were reported among vaccinated persons.

CONCLUSIONS

Our analyses do not suggest an increased number of GBS cases due to the vaccine. Awareness of expected rates of GBS is crucial when assessing adverse events following influenza immunization. Furthermore, since individuals with influenza infection are also at risk of developing GBS, they must be considered in such analyses, particularly if the vaccine campaign and disease are occurring concurrently.

Adverse events following pandemic influenza vaccine Pandemrix® reported in the French military forces--2009-2010

BACKGROUND

In the face of the A(H1N1) 2009 influenza pandemic, in October 2009 the French military health service (SSA) initiated a large vaccination campaign with Pandemrix(®) vaccine in the military forces. The aim of this study was to describe vaccine adverse events (VAE) reported during this campaign.

METHODS

VAE and the number of people vaccinated were surveyed by the SSA Epidemiological network across all military forces during the campaign, from October 2009 to April 2010. For each case, a notification form was completed, providing patient and clinical information. Three types of VAE were considered: non-serious, serious and unexpected.

RESULTS

There were 315.4 reported VAE per 100,000 vaccinations. Vaccination and VAE incidence rate peaks coincided with influenza epidemic peak in early December. The number of injected doses was 49,138, corresponding to a 14.5% vaccination coverage among military personnel, and 155 VAE were reported, including 5 serious VAE (1 Guillain-Barre syndrome, 2 malaises and 1 convulsive episode). Most VAE were non-serious (97.1%). Among these, 6 cases of local, rapidly regressive paresthesia were observed.

DISCUSSION

The military VAE surveillance system constitutes the only observatory on benign VAE in France. The reporting rate was much higher after the pandemic vaccine than after the seasonal vaccine, which may be a reflection of stimulated reporting. This report provides a useful description of VAE among military personnel during a mass emergency vaccination program, showing that the tolerance of the pandemic vaccine appeared acceptable.