JAMA：H1N1疫苗与格林-巴利综合征风险有关

格林-巴利综合征（GBS）常以快速发展的运动性功能虚弱和无反射（反射阙如）为特征。根据文章的背景资料：“该病被认为是自身免疫性疾病，并由某种外源刺激所触发。在1976-1977年间，人们发现在接种了灭活的‘猪’A型流感（H1N1）疫苗后，在美国出现了GBS的不寻常的高发生率。2003年，医药研究所（Institute of Medicine IOM）得出结论：证据倾向于接受在1976年的猪流感疫苗与成人中的GBS之间存在着因果关系。在随后的年份中，给予季节性流感疫苗的研究发现该风险增加幅度很小或没有。在对季节性流感疫苗、动物中的实验研究及在人群中的案例报告的流行病学研究所做的一项较为近来的评估中，IOM疫苗不良作用审查委员会得出结论，接受或否认存在某种因果关系的证据不足。”

加拿大魁北克市拉瓦尔大学的Philippe De Wals，M.D.，Ph.D等研究人员刊登在JAMA上一项研究旨在评估大流行性流感疫苗接种后的GBS风险。2009年秋季，魁北克启动了一场针对2009年A型流感（H1N1）大流行病毒株的疫苗接种活动。在该年底的时候，有440万居民接种了疫苗。该研究包括了在主动监测或在省医院出院总结数据库中的在2009年10月至2010年3月的6个月中的对由医生，其中大多数为神经内科医生，所报告的疑似及确认的GBS案子的跟踪。免疫接种的状态得到了核实。

在为期6个月的时间里发现了83例确认的GBS病例。25个被确认的病例是在起病前8周或不到8周时接受了2009年A型流感（H1N1）的疫苗接种，其中大多数人（19/25）是在起病前4周或不到4周时接种该疫苗的。数据分析表明，在接种了A型流感（H1N1）疫苗之后出现了GBS的小幅但明显的风险。归因于疫苗接种的病例数大约为每1百万剂中出现2例。仅在那些50岁或以上的人中观察到过度的风险。

文章的作者写道：“在魁北克，发生一例有记录的A型流感（H1N1 ）感染之后的个人住院的风险为1/2500，死亡风险为1/7，3000。该H1N1疫苗对防止感染及其并发症非常有效。很有可能该免疫接种的裨益要大于其风险。”

doi:10.1001/jama.2012.7342
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Risk of Guillain-Barré Syndrome Following H1N1 Influenza Vaccination in Quebec

Philippe De Wals, PhD; Geneviève Deceuninck, MD; Eveline Toth, MSc; Nicole Boulianne, MSc; Denis Brunet, MD; Renée-Myriam Boucher, MD; Monique Landry, MD; Gaston De Serres, PhD

Context In fall 2009 in Quebec, Canada, an immunization campaign was launched against the 2009 influenza A(H1N1) pandemic strain, mostly using an AS03 adjuvant vaccine. By the end of the year, 57% of the 7.8 million residents had been vaccinated. Objective To assess the risk of Guillain-Barré syndrome (GBS) following pandemic influenza vaccine administration. Design Population-based cohort study with follow-up over the 6-month period October 2009 through March 2010. The investigation was ordered by the chief medical officer of health in accordance with the Quebec Public Health Act. Setting All acute care hospitals and neurology clinics in Quebec. Population Suspected and confirmed GBS cases reported by physicians, mostly neurologists, during active surveillance or identified in the provincial hospital summary discharge database. Medical records were reviewed and cases classified according to Brighton Collaboration definitions (categorized as level 1, 2, or 3, corresponding to criteria of decreasing certainty in diagnosis). Immunization status was verified and denominators were estimated from the provincial immunization registry (4.4 million vaccinated) and census data (total target population aged ≥6 months, 7.8 million), with a total of 3 623 046 person-years of observation. Main Outcome Measures Relative and attributable risks were calculated using a Poisson model and the self-controlled case-series method. Results Over a 6-month period, 83 confirmed GBS cases were identified, including 71 Brighton level 1 through 3 cases. Twenty-five confirmed cases had been vaccinated against 2009 influenza A(H1N1) 8 or fewer weeks before disease onset, with most (19/25) vaccinated 4 or fewer weeks before onset. In the Poisson model, the age- and sex-adjusted relative risk was 1.80 (95% CI, 1.12-2.87) for all confirmed cases during the 8-week postvaccination period and was 2.75 (95% CI, 1.63-4.62) during the 4-week postvaccination period. Using the self-controlled case-series method, relative risk estimates during the 4-week postvaccination period were 3.02 (95% CI, 1.64-5.56) for all confirmed cases (n = 42) and 2.33 (95% CI, 1.19-4.57) for Brighton level 1 through 3 cases (n = 36). The number of GBS cases attributable to vaccination was approximately 2 per 1 million doses. There was no indication of an excess risk in persons younger than 50 years. Conclusions In Quebec, the 2009 influenza A(H1N1) vaccine was associated with a small but significant risk of GBS. It is likely that the benefits of immunization outweigh the risks. Guillain-Barré syndrome (GBS) is a peripheral neuropathy with acute onset and is characterized, in its typical presentation, by rapidly developing motor weakness and areflexia.1 - 2 The disease is thought to be autoimmune and triggered by a stimulus of external origin.1 - 2 In 1976-1977, an unusually high rate of GBS was identified in the United States following the administration of inactivated “swine” influenza A(H1N1) vaccines.3 In 2003, the Institute of Medicine (IOM) concluded that the evidence favored acceptance of a causal relationship between the 1976 swine influenza vaccines and GBS in adults.4 Studies of seasonal influenza vaccines administered in subsequent years have found small or no increased risk.5 In mice, different influenza vaccines can induce antiganglioside antibodies that are associated with the development of GBS in humans.6 Extrapolation of results of animal studies to humans, however, is difficult. In a more recent assessment of epidemiologic studies on seasonal influenza vaccines, experimental studies in animals, and case reports in humans, the IOM Committee to Review Adverse Effects of Vaccines concluded that the evidence was inadequate to accept or reject a causal relationship.7 In the province of Quebec, Canada, a mass immunization campaign was launched in the fall of 2009 to control a pandemic caused by a new influenza A(H1N1) virus.8 - 9 Herein we report results of a population-based epidemiologic investigation ordered by the chief medical officer of health, based on GBS cases notified to public health authorities and others found in the MEDECHO provincial hospitalization database.