Narcolepsy as an adverse event following immunization: Case definition and guidelines for data collection, analysis and presentation

Is there a role for repeating the multiple sleep latency test across childhood when initially non-diagnostic?

BACKGROUND

The gold standard investigation for central disorders of hypersomnolence is the Multiple Sleep Latency Test (MSLT). As the clinical features of these disorders of hypersomnolence evolve with time in children, clinicians may consider repeating a previously non-diagnostic MSLT. Currently there are no guidelines available regards the utility and timing of repeating paediatric MSLTs.

METHODS

Retrospective review of children aged 3-18years with ≥2MSLTs between 2005 and 2022. Narcolepsy was defined as mean sleep latency (MSL) <8min with ≥2 sleep onset REM (SOREM); idiopathic hypersomnia (IH) was defined as MSL <8min with <2 SOREM. MSLTs not meeting these criteria were labelled non-diagnostic.

RESULTS

19 children (9 female) with initial non-diagnostic MSLT underwent repeat MSLT, with 6 proceeding to a 3rd MSLT following 2 non-diagnostic MSLTs. The 2nd MSLT resulted in diagnosis in 6/19 (32 %) (3 narcolepsy, 3 IH); and 2/6 (33 %) 3rd MSLT were diagnostic (2 IH). Median age at initial MSLT was 7.5y (range 3.4-17.8y), with repeat performed after median of 2.9y (range 0.9-8.2y), and 3rd after a further 1.9 years (range 1.2-4.2y). Mean change in MSL on repeat testing was -2min (range -15.5min to +4.9min, p = 0.18). Of the 8 diagnostic repeat MSLTs, in addition to the MSL falling below 8 min, 2 children also developed ≥2 SOREM that had not been previously present.

CONCLUSIONS

A third of repeat MSLTs became diagnostic, suggesting repeat MSLT should be considered in childhood if clinical suspicion persists. Further work needs to address the ideal interval between MSLTs and diagnostic cut-points specific to the paediatric population.

Lessons learned from COVID-19, H1N1, and routine vaccine pharmacovigilance in the United States: a path to a more robust vaccine safety program

INTRODUCTION

Vaccine pharmacovigilance is an essential component of vaccine safety programs. Vaccine pharmacovigilance refers to detecting uncommon adverse events following immunization (AEFI), determining whether they are due to the vaccine or are only a coincidence, and, for those AEFI considered related to vaccination, characterizing them further. When AEFI are due to vaccination, it is important to characterize the attributable risk and ascertain the biological mechanism causing the adverse reaction to inform efforts to prevent or mitigate the risk. A robust post-authorization safety system is necessary for vaccine decision-making, clinical recommendations, vaccine compensation, and vaccine communication and confidence.

AREAS COVERED

This paper describes the key characteristics of vaccine pharmacovigilance programs, reviews US vaccine pharmacovigilance for routine vaccination programs, COVID-19, and H1N1, and makes recommendations for improving future vaccine safety systems.

EXPERT OPINION

The key characteristics of vaccine pharmacovigilance programs include passive surveillance, active surveillance, clinical investigation and special studies, and causality assessment. Recent examples illustrate the strengths of US pharmacovigilance systems, including systems for passive and active surveillance, as well as areas for improvement, including study of pathogenesis, consistent funding, and leadership. We make recommendations that would, if implemented, further strengthen the vaccine safety system for future routine and pandemic immunizations.

Sleepy Kids: are the current diagnostic criteria for multiple sleep latency tests enough?

Excessive daytime sleepiness (EDS) is common in childhood and is currently quantified using adult criteria on a multiple sleep latency test (MSLT). This study aimed to describe paediatric MSLT results, particularly focussing on a previously proposed alternative mean sleep latency (MSL) threshold for children of 12 min, and assess the impact of a 5th nap. We performed a retrospective analysis of MSLTs at a single paediatric centre from 2004 to 2021. Narcolepsy was defined as a mean sleep latency (MSL) ≤8min with ≥2 sleep onset REM (SOREM) periods. Idiopathic Hypersomnia (IH) was defined as a MSL ≤8min with <2 SOREMs. An ambiguous MSLT result was defined as a MSL 8-12min and/or ≥2 SOREM periods. Of 214 MSLTs [50 % female, median age 14.0y (range 3.3-20.1y)], narcolepsy was diagnosed in 48 (22 %), IH in 22 (10 %) and the result was ambiguous in 44 (21 %). Those with ambiguous MSLT results were older (15.6 vs 13.4y, p = 0.006) with a higher proportion of females (61 % vs 35 %, p = 0.01) in comparison to the narcolepsy group. A 5th nap was performed in 60 (28 %) of MSLTs and only changed the outcome in one case. In conclusion, MSLT results are borderline in 21 % of paediatric cases, suggesting that current adult diagnostic criteria may miss narcolepsy and IH in children. A 5th nap usually makes no difference or increases the MSL, suggesting that a four nap MSLT protocol could be used apart from rare cases where the result is borderline after the 4th nap.

Narcolepsy-A Neuropathological Obscure Sleep Disorder: A Narrative Review of Current Literature

Narcolepsy is a chronic, long-term neurological disorder characterized by a decreased ability to regulate sleep-wake cycles. Some clinical symptoms enter into differential diagnosis with other neurological diseases. Excessive daytime sleepiness and brief involuntary sleep episodes are the main clinical symptoms. The majority of people with narcolepsy experience cataplexy, which is a loss of muscle tone. Many people experience neurological complications such as sleep cycle disruption, hallucinations or sleep paralysis. Because of the associated neurological conditions, the exact pathophysiology of narcolepsy is unknown. The differential diagnosis is essential because relatively clinical symptoms of narcolepsy are easy to diagnose when all symptoms are present, but it becomes much more complicated when sleep attacks are isolated and cataplexy is episodic or absent. Treatment is tailored to the patient's symptoms and clinical diagnosis. To facilitate the diagnosis and treatment of sleep disorders and to better understand the neuropathological mechanisms of this sleep disorder, this review summarizes current knowledge on narcolepsy, in particular, genetic and non-genetic associations of narcolepsy, the pathophysiology up to the inflammatory response, the neuromorphological hallmarks of narcolepsy, and possible links with other diseases, such as diabetes, ischemic stroke and Alzheimer's disease. This review also reports all of the most recent updated research and therapeutic advances in narcolepsy. There have been significant advances in highlighting the pathogenesis of narcolepsy, with substantial evidence for an autoimmune response against hypocretin neurons; however, there are some gaps that need to be filled. To treat narcolepsy, more research should be focused on identifying molecular targets and novel autoantigens. In addition to therapeutic advances, standardized criteria for narcolepsy and diagnostic measures are widely accepted, but they may be reviewed and updated in the future with comprehension. Tailored treatment to the patient's symptoms and clinical diagnosis and future treatment modalities with hypocretin agonists, GABA agonists, histamine receptor antagonists and immunomodulatory drugs should be aimed at addressing the underlying cause of narcolepsy.

Narcolepsy in Children: Sleep disorders in children, A rapidly evolving field seeking consensus

Narcolepsy is a life-long sleep disorder with two distinct subtypes, narcolepsy type I and narcolepsy type II. It is now well recognized that the loss of hypocretin neurons underlies the pathogenesis of narcolepsy type I, however, the pathogenesis of narcolepsy type II is currently unknown. Both genetic and environmental factors play an important role in the pathogenesis of narcolepsy. There is increasing evidence that autoimmune processes may play a critical role in the loss of hypocretin neurons. Infections especially streptococcus and influenza have been proposed as a potential trigger for the autoimmune-mediated mechanism. Several recent studies have shown increased cases of pediatric narcolepsy following the 2009 H1N1 pandemic. The increased cases in Europe seem to be related to a specific type of H1N1 influenza vaccination (Pandemrix), while the increased cases in China are related to influenza infection. Children with narcolepsy can have an unusual presentation at disease onset including complex motor movements which may lead to delayed diagnosis. All classic narcolepsy tetrads are present in only a small proportion of children. The diagnosis of narcolepsy is confirmed by either obtaining cerebrospinal fluid hypocretin or overnight sleep study with the multiple sleep latency test (MSLT). There are limitations of using MSLT in young children such that a negative MSLT test cannot exclude narcolepsy. HLA markers have limited utility in narcolepsy, but it may be useful in young children with clinical suspicion of narcolepsy. For management, both pharmacologic and non-pharmacologic treatments are important in the management of narcolepsy. Pharmacotherapy is primarily aimed to address excessive daytime sleepiness and REM-related symptoms such as cataplexy. In addition to pharmacotherapy, routine screening of behavioral and psychosocial issues is warranted to identify patients who would benefit from bio-behavior intervention.

Misdiagnosis of narcolepsy caused by a false positive orexin-A/hypocretin-1 enzyme immune assay

The diagnosis of narcolepsy is based on clinical history, sleep studies, and, in some cases, cerebrospinal fluid orexin-A/hypocretin-1 measurement. The gold standard for orexin measurement is the radioimmune assay (RIA), but other commercial kits are also available, such as the enzyme immune assay (EIA). The specificity of orexin EIA in humans is unknown. We report four cases where orexin levels were measured by EIA and resulted in false positives and the misdiagnosis of narcolepsy. Therefore, orexin EIA measurement should be strongly discouraged in a clinical setting.

Narcolepsy with intermediate cerebrospinal level of hypocretin-1

STUDY OBJECTIVES

To describe the phenotype of narcolepsy with intermediate cerebrospinal hypocretin-1 levels (CSF hcrt-1).

METHODS

From 1600 consecutive patients with narcolepsy from Bologna and Montpellier sleep centers we selected patients with intermediate CSF hcrt-1 levels (110-200 pg/ml). Clinical, neurophysiological and biological data were contrasted for the presence of cataplexy, HLA-DQB1*06:02, and median CSF hcrt-1 levels (149.34 pg/mL).

RESULTS

Forty-five (55% males, aged 35 ± 17 years) patients (2.8% of all cases) were included. Thirty-three (73%) were HLA-DQB1*06:02, 29 (64%) reported cataplexy (21, 72.4% with typical features), and 5 (11%) had presumed secondary etiology. Cataplexy was associated with other core narcolepsy symptoms, increased sleep onset REM periods, and nocturnal sleep disruption. Cataplexy and irrepressible daytime sleep were more frequent in HLA DQB1*06:02 positive patients. Lower CSF hcrt-1 levels were associated with hallucinations.

CONCLUSION

Narcolepsy with intermediate CSF hcrt-1 level is a rare condition with heterogeneous phenotype. HLA DQB1*06:02 and lower CSF hcrt-1 were associated with typical narcolepsy features, calling for future research to distinguish incomplete from secondary narcolepsy forms.

Narcolepsy in children and young people in Ireland: 2006-2017

AIM

To describe the population of young people in Ireland diagnosed with narcolepsy with regards to vaccine exposure, symptomatology, investigation results and experience of medical treatment.

METHOD

Retrospective review of medical records at the single tertiary referral centre for young people with narcolepsy in Ireland.

RESULTS

Sixty-seven patients were diagnosed with narcolepsy between July 2006 and July 2017. Sixty-one (91%) of these developed symptoms after receiving the Pandemrix vaccine. The population was largely homogeneous with low hypocretin (87.5%), HLA DQB1∗0602 positivity (95%) and unremarkable findings on MRI Brain (100%). 77.6% experienced cataplexy; we also measured high levels of obesity, school non-attendance and psychosocial complexity. Symptoms often continued despite treatment, with multiple medications prescribed in 76.1% of patients. Prescription of sodium oxybate was associated with a significant reduction in BMI standard deviation scores at 6 months, with improved IOTF obesity scores seen at 36 month follow-up.

CONCLUSIONS

This paper describes the experience of narcolepsy in children and young people in Ireland from 2006 - 2017 at the national tertiary referral centre. Narcolepsy in children and young people in Ireland carries a significant burden of illness, with impact on participation in education as well as physical and mental health. Symptoms can be refractory to medical treatment. Referral to tertiary centres for prompt treatment and multidisciplinary input is essential.

[Recommendations on the approach when unusual neurological symptoms occur in temporal association with vaccinations in childhood and adolescence]

Vaccinations are often administered at an age when many neurological diseases of childhood and adolescence also occur. Febrile seizures may occur following vaccination in patients with an appropriate genetic predisposition. The occurrence of narcolepsy has been described more frequently after pandemic influenza A-H1N1 vaccinations. The causality has not been proven. Data regarding an association between Guillain-Barré syndrome and influenza vaccinations are inconclusive. It was conclusively shown that vaccinations do not cause neurological disorders, such as autism and do not trigger multiple sclerosis. In summary, there is currently no confirmed evidence for the occurrence of chronic neurological diseases as a consequence of generally recommended vaccinations in Germany. If unusual neurological symptoms are observed in temporal association with vaccinations, a comprehensive evaluation is necessary to exclude a causal relationship and to diagnose the underlying neurological disease independent of the vaccination. This statement gives specific recommendations for the practical approach when neurological symptoms are observed in temporal association with vaccinations with respect to taking the patient history, initial diagnostic procedures, accurate and prompt documentation and the obligation to report the event. The committee also proposes procedures for further clarification and differential diagnostics of causal neurological diseases in childhood and adolescence.

Prevalence and incidence of narcolepsy in a US health care claims database, 2008-2010

STUDY OBJECTIVES

To determine the prevalence and incidence of narcolepsy using a large US health care claims database.

METHODS

The Truven Health MarketScan Commercial Dissertation Database (THMCDD) was used to estimate prevalence and incidence of narcolepsy, with and without cataplexy, by age groups, gender, and region among patients under age 66 years with continuous enrollment for years 2008-2010. THMCDD contains health claims information for more than 18 million people. Prevalence was expressed as cases/100 000 persons. Average annual incidence (using varying criteria for latency between the diagnostic tests, polysomnograph coupled with multiple sleep latency test [MSLT], and the diagnosis) was expressed as new cases/100 000 persons/year.

RESULTS

There were 8 444 517 continuously enrolled patients and 6703 diagnosed with narcolepsy (prevalence overall: 79.4/100 000; without cataplexy: 65.4/100 000; with cataplexy: 14.0/100 000). On the basis of the three definitions of incidence, overall average annual incidence was 7.67, 7.13, and 4.87/100 000 persons/year. Incidence for narcolepsy without cataplexy was generally several times higher than narcolepsy with cataplexy. Prevalence and incidence were approximately 50% greater for females compared to males across most age groups. Prevalence was highest among the 21-30 years age group, with incidence highest among enrollees in their early 20s and late teens. Regionally, the North Central United States had the highest prevalence and incidence, whereas the West was the lowest.

CONCLUSION

We found greater prevalence and incidence of narcolepsy (including without cataplexy) than most previous studies. The increased proportions in females, enrollees in their early 20s, and US regional differences require further study. Increased awareness and early identification is critical in the management of this burdensome condition.

Validation of Multiple Sleep Latency Test for the diagnosis of pediatric narcolepsy type 1

Objective

To validate polysomnographic markers (sleep latency and sleep-onset REM periods [SOREMPs] at the Multiple Sleep Latency Test [MSLT] and nocturnal polysomnography [PSG]) for pediatric narcolepsy type 1 (NT1) against CSF hypocretin-1 (hcrt-1) deficiency and presence of cataplexy, as no criteria are currently validated in children.

Methods

Clinical, neurophysiologic, and, when available, biological data (HLA-DQB1*06:02 positivity, CSF hcrt-1 levels) of 357 consecutive children below 18 years of age evaluated for suspected narcolepsy were collected. Best MSLT cutoffs were obtained by receiver operating characteristic (ROC) curve analysis by contrasting among patients with available CSF hcrt-1 assay (n = 228) with vs without CSF hcrt-1 deficiency, and further validated in patients without available CSF hcrt-1 against cataplexy (n = 129).

Results

Patients with CSF hcrt-1 deficiency were best recognized using a mean MSLT sleep latency ≤8.2 minutes (area under the ROC curve of 0.985), or by at least 2 SOREMPs at the MSLT (area under the ROC curve of 0.975), or the combined PSG + MSLT (area under the ROC curve of 0.977). Although specificity and sensitivity of reference MSLT sleep latency ≤8 minutes and ≥2 SOREMPs (nocturnal SOREMP included) was 100% and 94.87%, the combination of MSLT sleep latency and SOREMP counts did not improve diagnostic accuracy. Age or sex also did not significantly influence these results in our pediatric population.

Conclusions

At least 2 SOREMPs or a mean sleep latency ≤8.2 minutes at the MSLT are valid and reliable markers for pediatric NT1 diagnosis, a result contrasting with adult NT1 criteria.

Classification of evidence

This study provides Class III evidence that for children with suspected narcolepsy, polysomnographic and MSLT markers accurately identify those with narcolepsy type 1.

[A Child's Sleep: A Book with Seven Seals? A Guide to Systematic Problem Identification and Solution]

A Child's Sleep: A Book with Seven Seals? A Guide to Systematic Problem Identification and Solution Abstract. The sleep of a child can be influenced and sometimes disturbed by many, often development-associated, phenomena. This results not only in a burden for the child, but regularly also for the parents, who in their need for help, often seek the advice of the attending physician. The child- and adolescent-specific questionnaire BEARS, which was developed by J. Owens and K. Mindell, allows the first diagnostic steps and classifications based on the most important symptoms such as bedtime problems, excessive daytime sleepiness, waking up at night, problems with regularity and sleep duration as well as nocturnal breathing disorders. The aim of this article is to show that important conclusions can be drawn in the everyday practice as to which symptoms need to be clarified how and how urgently, and which belong in the hands of a specialized sleep center.

Narcolepsy and adjuvanted pandemic influenza A (H1N1) 2009 vaccines - Multi-country assessment

BACKGROUND

In 2010, a safety signal was detected for narcolepsy following vaccination with Pandemrix, an AS03-adjuvanted monovalent pandemic H1N1 influenza (pH1N1) vaccine. To further assess a possible association and inform policy on future use of adjuvants, we conducted a multi-country study of narcolepsy and adjuvanted pH1N1 vaccines.

METHODS

We used electronic health databases to conduct a dynamic retrospective cohort study to assess narcolepsy incidence rates (IR) before and during pH1N1 virus circulation, and after pH1N1 vaccination campaigns in Canada, Denmark, Spain, Sweden, Taiwan, the Netherlands, and the United Kingdom. Using a case-control study design, we evaluated the risk of narcolepsy following AS03- and MF59-adjuvanted pH1N1 vaccines in Argentina, Canada, Spain, Switzerland, Taiwan, and the Netherlands. In the Netherlands, we also conducted a case-coverage study in children born between 2004 and 2009.

RESULTS

No changes in narcolepsy IRs were observed in any periods in single study sites except Sweden and Taiwan; in Taiwan incidence increased after wild-type pH1N1 virus circulation and in Sweden (a previously identified signaling country), incidence increased after the start of pH1N1 vaccination. No association was observed for Arepanrix-AS03 or Focetria-MF59 adjuvanted pH1N1 vaccines and narcolepsy in children or adults in the case-control study nor for children born between 2004 and 2009 in the Netherlands case-coverage study for Pandemrix-AS03.

CONCLUSIONS

Other than elevated narcolepsy IRs in the period after vaccination campaigns in Sweden, we did not find an association between AS03- or MF59-adjuvanted pH1N1 vaccines and narcolepsy in children or adults in the sites studied, although power to evaluate the AS03-adjuvanted Pandemrix brand vaccine was limited in our study.

Innovative Digital Tools and Surveillance Systems for the Timely Detection of Adverse Events at the Point of Care: A Proof-of-Concept Study

INTRODUCTION AND OBJECTIVE

Regulatory authorities often receive poorly structured safety reports requiring considerable effort to investigate potential adverse events post hoc. Automated question-and-answer systems may help to improve the overall quality of safety information transmitted to pharmacovigilance agencies. This paper explores the use of the VACC-Tool (ViVI Automated Case Classification Tool) 2.0, a mobile application enabling physicians to classify clinical cases according to 14 pre-defined case definitions for neuroinflammatory adverse events (NIAE) and in full compliance with data standards issued by the Clinical Data Interchange Standards Consortium.

METHODS

The validation of the VACC-Tool 2.0 (beta-version) was conducted in the context of a unique quality management program for children with suspected NIAE in collaboration with the Robert Koch Institute in Berlin, Germany. The VACC-Tool was used for instant case classification and for longitudinal follow-up throughout the course of hospitalization. Results were compared to International Classification of Diseases , Tenth Revision (ICD-10) codes assigned in the emergency department (ED).

RESULTS

From 07/2013 to 10/2014, a total of 34,368 patients were seen in the ED, and 5243 patients were hospitalized; 243 of these were admitted for suspected NIAE (mean age: 8.5 years), thus participating in the quality management program. Using the VACC-Tool in the ED, 209 cases were classified successfully, 69 % of which had been missed or miscoded in the ED reports. Longitudinal follow-up with the VACC-Tool identified additional NIAE.

CONCLUSION

Mobile applications are taking data standards to the point of care, enabling clinicians to ascertain potential adverse events in the ED setting and during inpatient follow-up. Compliance with Clinical Data Interchange Standards Consortium (CDISC) data standards facilitates data interoperability according to regulatory requirements.

Temporal Changes in the Cerebrospinal Fluid Level of Hypocretin-1 and Histamine in Narcolepsy

Study Objectives:

To follow the temporal changes of cerebrospinal fluid (CSF) biomarker levels in narcoleptic patients with unexpected hypocretin level at referral.

Methods:

From 2007 to 2015, 170 human leukocyte antigen (HLA) DQB1*06:02-positive patients with primary narcolepsy and definite (n = 155, 95 males, 60 females, 36 children) or atypical cataplexy (n = 15, 4 males, 3 children) were referred to our center. Cerebrospinal hypocretin deficiency was found in 95.5% and 20% of patients with definitive and atypical cataplexy, respectively. CSF hypocretin-1 (n = 6) and histamine/tele-methylhistamine (n = 5) levels were assessed twice (median interval: 14.4 months) in four patients with definite and in two with atypical cataplexy and hypocretin level greater than 100 pg/mL at baseline.

Results:

CSF hypocretin levels decreased from normal/intermediate to undetectable levels in three of the four patients with definite cataplexy and remained stable in the other (>250 pg/mL). Hypocretin level decreased from 106 to 27 pg/mL in one patient with atypical cataplexy, and remained stable in the other (101 and 106 pg/mL). CSF histamine and tele-methylhistamine levels remained stable, but for one patient showing increased frequency of cataplexy and a strong decrease (−72.5%) of tele-methylhistamine levels several years after disease onset. No significant association was found between relative or absolute change in hypocretin level and demographic/clinical features.

Conclusions:

These findings show that in few patients with narcolepsy with cataplexy, symptoms and CSF marker levels can change over time. In these rare patients with cataplexy without baseline hypocretin deficiency, CSF markers should be monitored over time with potential for immune therapies in early stages to try limiting hypocretin neuron loss.

Incidence of narcolepsy after H1N1 influenza and vaccinations: Systematic review and meta-analysis

An increased incidence of narcolepsy was seen in many countries after the pandemic H1N1 influenza vaccination campaign in 2009-2010. The H1N1 vaccine - narcolepsy connection is based on observational studies that are prone to various biases, e.g., confounding by H1N1 infection, and ascertainment, recall and selection biases. A direct pathogenic link has, however, remained elusive. We conducted a systematic review and meta-analysis to analyze the magnitude of H1N1 vaccination related risk and to examine if there was any association with H1N1 infection itself. We searched all articles from PubMed, Web of Science and Scopus, and other relevant sources reporting the incidence and risk of post-vaccine narcolepsy. In our paper, we show that the risk appears to be limited to only one vaccine (Pandemrix^®). During the first year after vaccination, the relative risk of narcolepsy was increased 5 to 14-fold in children and adolescents and 2 to 7-fold in adults. The vaccine attributable risk in children and adolescents was around 1 per 18,400 vaccine doses. Studies from Finland and Sweden also appear to demonstrate an extended risk of narcolepsy into the second year following vaccination, but such conclusions should be interpreted with a word of caution due to possible biases. Benefits of immunization outweigh the risk of vaccination-associated narcolepsy, which remains a rare disease.

The immunogenetics of narcolepsy associated with A(H1N1)pdm09 vaccination (Pandemrix) supports a potent gene-environment interaction

The influenza A(H1N1)pdm09 vaccination campaign from 2009 to 2010 was associated with a sudden increase in the incidence of narcolepsy in several countries. Narcolepsy with cataplexy is strongly associated with the human leukocyte antigen (HLA) class II DQB1*06:02 allele, and protective associations with the DQB1*06:03 allele have been reported. Several non-HLA gene loci are also associated, such as common variants of the T-cell receptor-α (TRA), the purinergic receptor P2RY11, cathepsin H (CTSH) and TNFSF4/OX40L/CD252. In this retrospective multicenter study, we investigated if these predisposing gene loci were also involved in vaccination-associated narcolepsy. We compared HLA- along with single-nucleotide polymorphism genotypes for non-HLA regions between 42 Pandemrix-vaccinated narcolepsy cases and 1990 population-based controls. The class II gene loci associations supported previous findings. Nominal association (P-value<0.05) with TRA as well as suggestive (P-value<0.1) associations with P2RY11 and CTSH were found. These associations suggest a very strong gene-environment interaction, in which the influenza A(H1N1)pdm09 strain or Pandemrix vaccine can act as potent environmental triggers.

Retrospective multicenter matched case-control study on the risk factors for narcolepsy with special focus on vaccinations (including pandemic influenza vaccination) and infections in Germany

OBJECTIVE

Studies associate pandemic influenza vaccination with narcolepsy. In Germany, a retrospective, multicenter, matched case-control study was performed to identify risk factors for narcolepsy, particularly regarding vaccinations (seasonal and pandemic influenza vaccination) and infections (seasonal and pandemic influenza) and to quantify the detected risks.

METHODS

Patients with excessive daytime sleepiness who had been referred to a sleep center between April 2009 and December 2012 for multiple sleep latency test (MSLT) were eligible. Case report forms were validated according to the criteria for narcolepsy defined by the Brighton Collaboration (BC). Confirmed cases of narcolepsy (BC level of diagnostic certainty 1-4a) were matched with population-based controls by year of birth, gender, and place of residence. A second control group was established including patients in whom narcolepsy was definitely excluded (test-negative controls).

RESULTS

A total of 103 validated cases of narcolepsy were matched with 264 population-based controls. The second control group included 29 test-negative controls. A significantly increased odd ratio (OR) to develop narcolepsy (crude OR [cOR] = 3.9, 95% confidence interval [CI] = 1.8-8.5; adjusted OR [aOR] = 4.5, 95% CI = 2.0-9.9) was detected in individuals immunized with pandemic influenza A/H1N1/v vaccine prior to symptoms onset as compared to nonvaccinated individuals. Using test-negative controls, in individuals immunized with pandemic influenza A/H1N1/v vaccine prior to symptoms onset, a nonsignificantly increased OR of narcolepsy was detected when compared to nonvaccinated individuals (whole study population, BC levels 1-4a: cOR = 1.9, 95% CI = 0.5-6.9; aOR = 1.8, 95% CI = 0.3-10.1).

CONCLUSIONS

The findings of this study support an increased risk for narcolepsy after immunization with pandemic influenza A/H1N1/v vaccine.

Narcolepsy and hypersomnia in Norwegian children and young adults following the influenza A(H1N1) 2009 pandemic

BACKGROUND

Associations between influenza infection and sleep disorders are poorly studied. We investigated if pandemic influenza infection or vaccination with Pandemrix in 2009/2010 was associated with narcolepsy or hypersomnia in children and young adults.

METHODS

We followed the Norwegian population under age 30 from January 2008 through December 2012 by linking national health registry data. Narcolepsy diagnoses were validated using hospital records. Risks of narcolepsy or hypersomnia were estimated as adjusted hazard ratios (HRs) in Cox regression models with influenza infection and vaccination as time-dependent exposures.

RESULTS

Among the 1,638,526 persons under age 30 in Norway in 2009, 3.6% received a physician diagnosis of influenza during the pandemic, while 41.9% were vaccinated against pandemic influenza. Between October 1st 2009 and December 31st 2012, 72 persons had onset of narcolepsy and 305 were diagnosed with hypersomnia. The risk of a sleep disorder was associated with infection during the first six months, adjusted HR 3.31 with 95% confidence interval [CI], 1.01-10.79 for narcolepsy and adjusted HR 3.13 (95% CI, 1.12-8.76) for hypersomnia. The risk of narcolepsy was strongly associated with vaccination during the first six months adjusted HR 17.21 (95% CI, 6.28-47.14), while the adjusted HR for hypersomnia was 1.54 (95% CI, 0.81-2.93).

CONCLUSIONS

The study confirms an increased HR of narcolepsy following pandemic vaccination. Slightly increased HRs of narcolepsy and hypersomnia are also seen after influenza infection. However, the role of infection should be viewed with caution due to underreporting of influenza.

Narcolepsy Type 1 Is Associated with a Systemic Increase and Activation of Regulatory T Cells and with a Systemic Activation of Global T Cells

Narcolepsy is a rare neurologic disorder characterized by excessive daytime sleepiness, cataplexy and disturbed nocturnal sleep patterns. Narcolepsy type 1 (NT1) has been shown to result from a selective loss of hypothalamic hypocretin-secreting neurons with patients typically showing low CSF-hypocretin levels (<110 pg/ml). This specific loss of hypocretin and the strong association with the HLA-DQB1*06:02 allele led to the hypothesis that NT1 could be an immune-mediated pathology. Moreover, susceptibility to NT1 has recently been associated with several pathogens, particularly with influenza A H1N1 virus either through infection or vaccination. The goal of this study was to compare peripheral blood immune cell populations in recent onset pediatric NT1 subjects (post or non-post 2009-influenza A H1N1 vaccination) to healthy donors. We demonstrated an increased number of central memory CD4+ T cells (CD62L+ CD45RA-) associated to an activated phenotype (increase in CD69 and CD25 expression) in NT1 patients. Percentage and absolute count of regulatory T cells (Tregs) in NT1 patients were increased associated with an activated phenotype (increase in GITR and LAP expression), and of activated memory phenotype. Cytokine production by CD4+ and CD8+ T cells after activation was not modified in NT1 patients. In H1N1 vaccinated NT1 patients, absolute counts of CD3+, CD8+ T cells, and B cells were increased compared to non-vaccinated NT1 patients. These results support a global T cell activation in NT1 patients and thus support a T cell-mediated autoimmune origin of NT1, but do not demonstrate the pathological role of H1N1 prophylactic vaccination. They should prompt further studies of T cells, particularly of Tregs (such as suppression and proliferation antigen specific assays, and also T-cell receptor sequencing), in NT1.

Psychosocial intervention for children with narcolepsy:: Parents' expectations and perceived support

The study focuses on the parents of children who were affected by narcolepsy after a pandemic influenza and vaccination campaign in Finland. The main aim of the study was to clarify parents' expectations and perceived support from the intervention and to assess their need for additional support. The data were gathered using questionnaires. Fifty-eight parents answered the baseline questionnaire and 40 parents the final questionnaire. Parents' expectations of and perceived support from the intervention mainly related to peer support. The intervention offered an arena for sharing information and experiences and provided encouragement for coping in everyday life. Many expectations were not met, especially those concerning information about needed services, financial benefits and availability of local support. The results highlight that for persons with rare disorders and their families, an inpatient psychosocial intervention can offer an important arena to receive both informal and professionally led peer support. Comprehensive psychosocial and other support services are also needed in the community. Listening to parents' perspectives on the intervention and perceived support can help to establish multiform family-centred support for families with children affected by a rare chronic disabling condition.

Patterns of spontaneous reports on narcolepsy following administration of pandemic influenza vaccine; a case series of individual case safety reports in Eudravigilance

OBJECTIVE

This study aims to describe the frequency and quality of spontaneous narcolepsy case reports following administration of pandemic influenza vaccine as captured in the Eudravigilance database.

METHODS

We conducted a retrospective descriptive study of spontaneous Individual Case Safety Reports (ICSRs), reporting narcolepsy following administration of pandemic influenza vaccine as received by Eudravigilance until July 2014. De-duplication was carried out by Eudravigilance. Frequency of reporting is described as number of ICSRs received per month over time. The quality of the ICSRs was evaluated by completeness of information and diagnostic certainty using the Automated Brighton Collaboration case definition tool (ABC-tool) for narcolepsy.

RESULTS

After de-duplication, a total of 1333 ICSRs of narcolepsy and/or cataplexy following pandemic influenza vaccine were identified, originating from 18 countries worldwide. Most of the ICSRs (61.9%) originated from the signaling countries, Sweden and Finland. Although de-duplication of case reports was carried out, it is suspected that many duplicates exist, in particular from Sweden. The majority of the ICSRs (95.3%), reported exposure to Pandemrix®. Only few reports were received for Arepanrix® (1.6%) or Focetria® (0.5%), and Celvapan® (0.1%). Of those ICSRs reporting age, 73.1% concerned persons below age of 20years. When using the ABC-tool, all ICSRs were classified as having insufficient information to meet the Brighton Collaboration case definition of narcolepsy.

CONCLUSION

An increase in reporting of narcolepsy appeared in Eudravigilance only after awareness was raised by the national authorities. Most narcolepsy reports were received from countries where the signal initially occurred, and were related to Pandemrix® in children/adolescents. Basic information about the patient and the exposure was present in most of the ICSRs. The ICSRs captured by Eudravigilance however, do not collect enough information to assess the diagnostic certainty according to the Brighton Collaboration case definition.

Narcolepsy Following Yellow Fever Vaccination: A Case Report

Narcolepsy with cataplexy is a rare, but important differential diagnosis for daytime sleepiness and atonic paroxysms in an adolescent. A recent increase in incidence in the pediatric age group probably linked to the use of the Pandemrix influenza vaccine in 2009, has increased awareness that different environmental factors can “trigger” narcolepsy with cataplexy in a genetically susceptible population. Here, we describe the case of a 13-year-old boy with narcolepsy following yellow fever vaccination. He carries the HLA DQB1*0602 haplotype strongly associated with narcolepsy and cataplexy. Polysomnography showed rapid sleep onset with rapid eye movement (REM) latency of 47 min, significant sleep fragmentation and a mean sleep latency of 1.6 min with sleep onset REM in four out of four nap periods. Together with the clinical history, these findings are diagnostic of narcolepsy type 1. The envelope protein E of the yellow fever vaccine strain 17D has significant amino acid sequence overlap with both hypocretin and the hypocretin receptor 2 receptors in protein regions that are predicted to act as epitopes for antibody production. These findings raise the question whether the yellow fever vaccine strain may, through a potential molecular mimicry mechanism, be another infectious trigger for this neuro-immunological disorder.

Intermittent head drops: the differential spectrum

Intermittent Head Drops are episodic head flexion movements that can occur in a number of conditions. Typically, the term has mainly been related to epileptic episodes, but the spectrum of clinical conditions associated with this feature is wide-ranging even if never discussed in detail. By searching the electronic database, we may find that apart from the epileptic conditions, Intermittent Head Drops have been in fact reported in the setting of movement disorders, sleep disorders and even internal medicine disorders, such as Sandifer syndrome. We render an in-depth description of this characteristic phenomenon in different diseases, describing the clinical clues and neurophysiological patterns that may help the clinician to distinguish between the different settings of occurrence.

Application of Probabilistic Multiple-Bias Analyses to a Cohort- and a Case-Control Study on the Association between Pandemrix™ and Narcolepsy

Background

An increase in narcolepsy cases was observed in Finland and Sweden towards the end of the 2009 H1N1 influenza pandemic. Preliminary observational studies suggested a temporal link with the pandemic influenza vaccine Pandemrix™, leading to a number of additional studies across Europe. Given the public health urgency, these studies used readily available retrospective data from various sources. The potential for bias in such settings was generally acknowledged. Although generally advocated by key opinion leaders and international health authorities, no systematic quantitative assessment of the potential joint impact of biases was undertaken in any of these studies.

Methods

We applied bias-level multiple-bias analyses to two of the published narcolepsy studies: a pediatric cohort study from Finland and a case-control study from France. In particular, we developed Monte Carlo simulation models to evaluate a potential cascade of biases, including confounding by age, by indication and by natural H1N1 infection, selection bias, disease- and exposure misclassification. All bias parameters were evidence-based to the extent possible.

Results

Given the assumptions used for confounding, selection bias and misclassification, the Finnish rate ratio of 13.78 (95% CI: 5.72–28.11) reduced to a median value of 6.06 (2.5^th- 97.5^th percentile: 2.49–15.1) and the French odds ratio of 5.43 (95% CI: 2.6–10.08) to 1.85 (2.5^th—97.5^th percentile: 0.85–4.08).

Conclusion

We illustrate multiple-bias analyses using two studies on the Pandemrix^™-narcolepsy association and advocate their use to better understand the robustness of study findings. Based on our multiple-bias models, the observed Pandemrix^™-narcolepsy association consistently persists in the Finnish study. For the French study, the results of our multiple-bias models were inconclusive.

The safety of influenza vaccines in children: An Institute for Vaccine Safety white paper

Most influenza vaccines are generally safe, but influenza vaccines can cause rare serious adverse events. Some adverse events, such as fever and febrile seizures, are more common in children than adults. There can be differences in the safety of vaccines in different populations due to underlying differences in genetic predisposition to the adverse event. Live attenuated vaccines have not been studied adequately in children under 2 years of age to determine the risks of adverse events; more studies are needed to address this and several other priority safety issues with all influenza vaccines in children. All vaccines intended for use in children require safety testing in the target age group, especially in young children. Safety of one influenza vaccine in children should not be extrapolated to assumed safety of all influenza vaccines in children. The low rates of adverse events from influenza vaccines should not be a deterrent to the use of influenza vaccines because of the overwhelming evidence of the burden of disease due to influenza in children.

Autoimmune/inflammatory syndrome induced by adjuvants (ASIA): clues and pitfalls in the pediatric background

The development and increasing diffusion of new vaccinations and global immunization protocols have aroused burning debates about safety of adjuvants and their immunogenicity-enhancing effect in vaccines. Shoenfeld and Agmon-Levin have grouped under the term "autoimmune/inflammatory syndrome induced by adjuvants" (ASIA) a complex of variable signs and symptoms that may occur after a previous exposure to different adjuvants and also external environmental triggers, even eliciting specific overt immune-mediated disorders. This entity subsumes five medical conditions: post-vaccination phenomena, gulf war syndrome, macrophagic myofasciitis syndrome, siliconosis, and sick building syndrome, but the relevance and magnitude of the syndrome in the pediatric age is fundamentally limited to post-vaccination autoimmune or inflammatory disorders. The occurrence of vaccine-triggered phenomena represents a diagnostic challenge for clinicians and a research conundrum for many investigators. In this paper, we will analyze the general features of ASIA and focus on specific post-vaccination events in relation with the pediatric background. In the presence of a favorable genetic background, many autoimmune/inflammatory responses can be triggered by adjuvants and external factors, showing how the man himself might breach immune tolerance and drive many pathogenetic aspects of human diseases. Nonetheless, the elective application of ASIA diagnostic criteria to the pediatric population requires further assessment and evaluations. Additional studies are needed to help clarify connections between innate or adaptive immunity and pathological and/or protective autoantibodies mostly in the pediatric age, as children and adolescents are mainly involved in the immunization agendas related to vaccine-preventable diseases.

Nocturnal Sleep Dynamics Identify Narcolepsy Type 1

STUDY OBJECTIVES

To evaluate the reliability of nocturnal sleep dynamics in the differential diagnosis of central disorders of hypersomnolence.

DESIGN

Cross-sectional.

SETTING

Sleep laboratory.

PATIENTS

One hundred seventy-five patients with hypocretin-deficient narcolepsy type 1 (NT1, n = 79), narcolepsy type 2 (NT2, n = 22), idiopathic hypersomnia (IH, n = 22), and "subjective" hypersomnolence (sHS, n = 52).

INTERVENTIONS

None.

METHODS

Polysomnographic (PSG) work-up included 48 h of continuous PSG recording. From nocturnal PSG conventional sleep macrostructure, occurrence of sleep onset rapid eye movement period (SOREMP), sleep stages distribution, and sleep stage transitions were calculated. Patient groups were compared, and receiver operating characteristic (ROC) curve analysis was used to test the diagnostic utility of nocturnal PSG data to identify NT1.

RESULTS

Sleep macrostructure was substantially stable in the 2 nights of each diagnostic group. NT1 and NT2 patients had lower latency to rapid eye movement (REM) sleep, and NT1 patients showed the highest number of awakenings, sleep stage transitions, and more time spent in N1 sleep, as well as most SOREMPs at daytime PSG and at multiple sleep latency test (MSLT) than all other groups. ROC curve analysis showed that nocturnal SOREMP (area under the curve of 0.724 ± 0.041, P < 0.0001), percent of total sleep time spent in N1 (0.896 ± 0.023, P < 0.0001), and the wakefulness-sleep transition index (0.796 ± 0.034, P < 0.0001) had a good sensitivity and specificity profile to identify NT1 sleep, especially when used in combination (0.903 ± 0.023, P < 0.0001), similarly to SOREMP number at continuous daytime PSG (0.899 ± 0.026, P < 0.0001) and at MSLT (0.956 ± 0.015, P < 0.0001).

CONCLUSIONS

Sleep macrostructure (i.e. SOREMP, N1 timing) including stage transitions reliably identifies hypocretin-deficient narcolepsy type 1 among central disorders of hypersomnolence.

Incidence of narcolepsy before and after MF59-adjuvanted influenza A(H1N1)pdm09 vaccination in South Korean soldiers

BACKGROUND

Previous reports mostly from Europe suggested an association between an occurrence of narcolepsy and an influenza A(H1N1)pdm09 vaccine adjuvanted with AS03 (Pandemrix(®)). During the 2009 H1N1 pandemic vaccination campaign, the Korean military performed a vaccination campaign with one type of influenza vaccine containing MF59-adjuvants. This study was conducted to investigate the background incidence rate of narcolepsy in South Korean soldiers and the association of the MF59-adjuvanted vaccine with the occurrence of narcolepsy in a young adult group.

METHODS

To assess the incidence of narcolepsy, we retrospectively reviewed medical records of suspicious cases of narcolepsy in 2007-2013 in the whole 20 military hospitals of the Korean military. The screened cases were classified according to the Brighton Collaboration case definition of narcolepsy. After obtaining the number of confirmed cases of narcolepsy per 3 months in 2007-2013, we compared the crude incidence rate of narcolepsy before and after the vaccination campaign.

RESULTS

We included 218 narcolepsy suspicious cases in the initial review, which were screened by the diagnostic code on the computerized disease registry in 2007-2013. Forty-one cases were finally diagnosed with narcolepsy in 2007-2013 (male sex, 95%; median age, 21 years). The average background incidence rate of narcolepsy in Korean soldiers was 0.91 cases per 100,000 persons per year. During the 9 months before vaccination implementation (April to December 2009), 6 narcolepsy cases occurred, whereas during the next 9 months (January to September 2010) including the 3-month vaccination campaign, 5 cases occurred.

CONCLUSIONS

The incidence of narcolepsy in South Korean soldiers was not increased after the pandemic vaccination campaign using the MF59-adjuvanted vaccine. Our results suggest that the MF59-adjuvanted H1N1 vaccine did not contribute to the occurrence of narcolepsy in this young adult group.

Polysomnographic and actigraphic characteristics of patients with H1N1-vaccine-related and sporadic narcolepsy

OBJECTIVE

After the pandemic H1N1 influenza ASO3-adjuvanted vaccine, Pandemrix©, was used in late 2009 and early 2010, the incidence of narcolepsy increased in many European countries. This incidence mainly increased in children and adolescents and, to a lesser degree, in adults.

PATIENTS/METHODS

125 unmedicated patients, aged 4 to 61 years, were included in this case-series study. Of these, 69 were diagnosed to have an H1N1-vaccine-related narcolepsy and 57 had sporadic narcolepsy. Most of these patients had: an actigraphy recording of 1-2 weeks, polysomnography, a Multiple Sleep Latency Test (MSLT), and cerebrospinal fluid hypocretin-1 concentration analysis.

RESULTS

Patients with H1N1-vaccine-related narcolepsy had shorter diagnostic delays, lower periodic leg movement index during sleep, earlier sleep-wake rhythm, and were younger in age at diagnosis, compared with sporadic cases. They also had shorter sleep latency and more sleep onset REM periods in MSLT, but these results were strongly age-dependent. Actigraphy showed quantitatively less sleep and more sleep fragmentation than polysomnography.

CONCLUSION

Regarding polysomnographic and actigraphic characteristics, there were no dramatic deviations between H1N1-vaccine-related and sporadic narcolepsy. Circadian rhythms indicated some interesting new findings with respect to the H1N1-vaccine-related disease. An actigraphy recording of 1-2 weeks is useful when studying the nocturnal aspects of narcolepsy and sleep-wake rhythms of narcoleptic patients.

Clinical features of narcolepsy in children vaccinated with AS03 adjuvanted pandemic A/H1N1 2009 influenza vaccine in England

AIM

The aim of this study was to investigate whether children in England with narcolepsy who received the ASO3 adjuvanted pandemic A/H1N1 2009 influenza vaccine (Pandemrix) differed clinically from unvaccinated patients.

METHOD

A retrospective review was conducted in children with narcolepsy diagnosed by sleep centres and paediatric neurologists in 16 English hospitals. The inclusion criteria were patient age 4 to 18 years, onset of narcolepsy after January 2008, and diagnosis by the time of the key data-gathering visit in 2011. Clinical data came from hospital notes and general practitioner questionnaires. An expert panel validated the diagnoses.

RESULTS

Seventy-five patients with narcolepsy were identified (43 males, 32 females; mean age at onset 10y 4mo, range 3-18y). Of these patients, 11 received the Pandemrix vaccine before narcolepsy onset. On first presentation, there were more frequent reports of cataplexy, among other features, in vaccinated than in unvaccinated patients (82% vs 55%), but only excessive weight gain (55% vs 20%) was significantly more frequent (p=0.03). Facial hypotonia (p=0.03) and tongue protrusion (p=0.01) were eventually seen more frequently in vaccinated children. When considering patients diagnosed within a year of onset, vaccinated children were not diagnosed more rapidly than unvaccinated children.

INTERPRETATION

Some symptoms and signs of narcolepsy were more frequently reported in Pandemrix-vaccinated patients. There was no evidence of the more rapid diagnosis in vaccinated patients that has been reported in Finland and Sweden.

Case of early childhood-onset narcolepsy with cataplexy: comparison with a monozygotic co-twin

We describe here a rare case of early childhood-onset (5 years of age) narcolepsy. This case was interesting because of the ability to compare the patient's symptoms to the condition of her healthy monozygotic co-twin sister. The only environmental difference between the co-twins was head injury, which may be associated with the presence of narcolepsy. The co-twin was extroverted, sociable, reliable, and dexterous. In contrast, the patient could be described as introverted, gentle, honest and persevering, but was weak at conversation, assessment of a situation, memory, planning, activity (she was inactive), a sense of time, understanding of an analog clock, operating efficiency, and physical education (due to obesity). The sisters showed the same degree of appetite and dexterity with their fingers. Narcolepsy is often under-recognized or underdiagnosed, especially when the onset occurs in childhood. When we observe preschoolers with excessive daytime sleepiness, we should consider the possibility of narcolepsy with cataplexy.

[Narcolepsy]

Narcolepsy is a rare sleep disorder. The classical presentation includes the four symptoms excessive daytime sleepiness, cataplexy, sleep paralysis and hypnagogic hallucinations. As a model disease with all the transitions from awake to sleeping conditions, non-rapid eye movement (NREM) and rapid eye movement (REM), it plays an important role in neurology and sleep medicine. Patients with narcolepsy possess a reduced number of hypocretin-producing neurons in the hypothalamus and accordingly the hypocretin level in the cerebrospinal fluid is low. The neuropeptide hypocretin (orexin) has functions, such as the regulation of the sleep-wake cycle, the autonomous nerve system, motor system and metabolic processes. The delay in diagnosing narcolepsy is difficult to comprehend in modern medicine. The frequent association with other sleep-wake disorders may be responsible for the delay. Genomewide association studies have subsequently been able to prove that autoimmune mechanisms are responsible for the manifestation of narcolepsy with the HLA association being the most important for susceptibility and protection. Imaging studies have revealed neurodegenerative changes, making a multifactorial etiopathogenesis probable. The frequent occurrence of metabolic disorders has not yet been clarified. Early diagnosis of narcolepsy has the possibility to offer affected persons an adequate medication to lead an almost normal life and the future possibility to cure narcolepsy through immunomodulation therapy.

Risk of narcolepsy associated with inactivated adjuvanted (AS03) A/H1N1 (2009) pandemic influenza vaccine in Quebec

Context

An association between an adjuvanted (AS03) A/H1N1 pandemic vaccine and narcolepsy has been reported in Europe.

Objective

To assess narcolepsy risk following administration of a similar vaccine in Quebec.

Design

Retrospective population-based study.

Setting

Neurologists and lung specialists in the province were invited to report narcolepsy cases to a single reference centre.

Population

Patients were interviewed by two sleep experts and standard diagnostic tests were performed. Immunization status was verified in the provincial pandemic influenza vaccination registry.

Main Outcome Measures

Confirmed narcolepsy with or without cataplexy with onset of excessive daytime sleepiness between January 1^st, 2009, and December 31^st, 2010. Relative risks (RRs) were calculated using a Poisson model in a cohort analysis, by a self-controlled case series (SCCS) and a case-control method.

Results

A total of 24 cases were included and overall incidence rate was 1.5 per million person-years. A cluster of 7 cases was observed among vaccinated persons in the winter 2009–2010. In the primary cohort analysis, 16-week post-vaccination RR was 4.32 (95% CI: 1.50–11.12). RR was 2.07 (0.70–6.17) in the SCCS, and 1.48 (0.37–7.03) using the case-control method. Estimates were lower when observation was restricted to the period of pandemic influenza circulation, and tended to be higher in persons <20 years old and for cataplexy cases.

Conclusions

Results are compatible with an excess risk of approximately one case per million vaccine doses, mainly in persons less than 20 years of age. However, a confounding effect of the influenza infection cannot be ruled out.

Did narcolepsy occur following administration of AS03-adjuvanted A(H1N1) pandemic vaccine in Ontario, Canada? A review of post-marketing safety surveillance data

A vaccine safety signal and association between new onset of narcolepsy and AS03-adjuvanted pandemic influenza A(H1N1) vaccine (Pandemrix, GlaxoSmithKline) in children and young adults has been reported in several European countries. In Ontario, Canada, AS03-adjuvanted pandemic A(H1N1) vaccine (Arepanrix, GlaxoSmithKline) was the primary vaccine administered in 2009/10, with 4.8 million doses distributed. We assessed post-marketing safety surveillance data by extracting adverse events following immunisation (AEFIs) associated with this vaccine from the integrated Public Health Information System. Reports were screened for key terms related to narcolepsy and further limited to children and young adults four to 29 years of age. Of 1,604 AEFIs reported in Ontario, 53 reports met the search criteria. Individual assessment by a nurse consultant for additional context suggestive of narcolepsy yielded five reports for secondary medical review. None of the five reports proved consistent with a possible narcolepsy diagnosis based on the available information. We present the first post-marketing assessment from Canada of narcolepsy reports following receipt of Arepanix. Continued investigation of differences between Arepanrix and Pandemrix and subsequent risk of narcolepsy is indicated. In light of the limitations of passive surveillance to detect a signal in this instance, validation using other data sources is prudent.

Narcolepsy as an autoimmune disease: the role of H1N1 infection and vaccination

Narcolepsy is a sleep disorder characterised by loss of hypothalamic hypocretin (orexin) neurons. The prevalence of narcolepsy is about 30 per 100 000 people, and typical age at onset is 12-16 years. Narcolepsy is strongly associated with the HLA-DQB1*06:02 genotype, and has been thought of as an immune-mediated disease. Other risk genes, such as T-cell-receptor α chain and purinergic receptor subtype 2Y11, are also implicated. Interest in narcolepsy has increased since the epidemiological observations that H1N1 infection and vaccination are potential triggering factors, and an increase in the incidence of narcolepsy after the pandemic AS03 adjuvanted H1N1 vaccination in 2010 from Sweden and Finland supports the immune-mediated pathogenesis. Epidemiological observations from studies in China also suggest a role for H1N1 virus infections as a trigger for narcolepsy. Although the pathological mechanisms are unknown, an H1N1 virus-derived antigen might be the trigger.

Investigation of an association between onset of narcolepsy and vaccination with pandemic influenza vaccine, Ireland April 2009-December 2010

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Increased risk of narcolepsy in children and adults after pandemic H1N1 vaccination in France

An increased incidence of narcolepsy in children was detected in Scandinavian countries where pandemic H1N1 influenza ASO3-adjuvanted vaccine was used. A campaign of vaccination against pandemic H1N1 influenza was implemented in France using both ASO3-adjuvanted and non-adjuvanted vaccines. As part of a study considering all-type narcolepsy, we investigated the association between H1N1 vaccination and narcolepsy with cataplexy in children and adults compared with matched controls; and compared the phenotype of narcolepsy with cataplexy according to exposure to the H1N1 vaccination. Patients with narcolepsy-cataplexy were included from 14 expert centres in France. Date of diagnosis constituted the index date. Validation of cases was performed by independent experts using the Brighton collaboration criteria. Up to four controls were individually matched to cases according to age, gender and geographic location. A structured telephone interview was performed to collect information on medical history, past infections and vaccinations. Eighty-five cases with narcolepsy-cataplexy were included; 23 being further excluded regarding eligibility criteria. Of the 62 eligible cases, 59 (64% males, 57.6% children) could be matched with 135 control subjects. H1N1 vaccination was associated with narcolepsy-cataplexy with an odds ratio of 6.5 (2.1-19.9) in subjects aged<18 years, and 4.7 (1.6-13.9) in those aged 18 and over. Sensitivity analyses considering date of referral for diagnosis or the date of onset of symptoms as the index date gave similar results, as did analyses focusing only on exposure to ASO3-adjuvanted vaccine. Slight differences were found when comparing cases with narcolepsy-cataplexy exposed to H1N1 vaccination (n=32; mostly AS03-adjuvanted vaccine, n=28) to non-exposed cases (n=30), including shorter delay of diagnosis and a higher number of sleep onset rapid eye movement periods for exposed cases. No difference was found regarding history of infections. In this sub-analysis, H1N1 vaccination was strongly associated with an increased risk of narcolepsy-cataplexy in both children and adults in France. Even if, as in every observational study, the possibility that some biases participated in the association cannot be completely ruled out, the associations appeared robust to sensitivity analyses, and a specific analysis focusing on ASO3-adjuvanted vaccine found similar increase.

The autoimmune basis of narcolepsy

Narcolepsy is a neurological disorder characterized by excessive daytime sleepiness, cataplexy, hypnagonic hallucinations, sleep paralysis, and disturbed nocturnal sleep patterns. Narcolepsy is caused by the loss of hypocretin (orexin)-producing neurons in the lateral hypothalamus. Evidence, such as a strong association with HLA DQB1*06:02, strongly suggests an autoimmune basis targeting hypocretin neurons. Genome-wide association studies have strengthened the association between narcolepsy and immune system gene polymorphisms, including the identification of polymorphisms in the T cell receptor alpha locus, TNFSF4 (also called OX40L), Cathepsin H (CTSH) the purinergic receptor P2RY11, and the DNA methyltransferase DNMT1. Recently, attention has been raised regarding a spike in cases of childhood narcolepsy in 2010 following the 2009 H1N1 pandemic (pH1N1) in China and vaccination with Pandemrix, an adjuvanted H1N1 vaccine that was used in Europe. How the immune system may be involved in disease initiation and/or progression remains a challenge to researchers. Potential immunological pathways that could lead to the specific elimination of hypocretin producing neurons include molecular mimicry or bystander activation, and are likely a combination of genetic and environmental factors, such as upper airway infections.