Surveillance for Guillain-Barré syndrome after influenza vaccination among the Medicare population, 2009-2010

Current status of Guillain-Barré syndrome (GBS) in China: a 10-year comprehensive overview

Guillain-Barré syndrome (GBS) is an acute inflammatory polyradiculoneuropathy; a disease involving the peripheral nervous system which is the most common cause of acute flaccid paralysis worldwide. So far, it is still lack of a comprehensive overview and understanding of the national epidemiological, clinical characteristics, and the risk factors of GBS in China, as well as differences between China and other countries and regions in these respects. With the global outbreak of the coronavirus disease 2019 (COVID-19), an epidemiological or phenotypic association between severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and GBS has attracted great attention. In this review, we outlined the current clinical data of GBS in China by retrieving literature, extracting and synthesizing the data of GBS in China from 2010 to 2021. Besides, we compared the characteristics of epidemiology, preceding events and clinical profiles of GBS between China and other countries and regions. Furthermore, in addition to conventional intravenous immunoglobulin (IVIG) and plasma exchange (PE) therapy, the potential therapeutic effects with novel medications in GBS, such as complement inhibitors, etc., have become the research focus in treatments. We found that epidemiological and clinical findings of GBS in China are approximately consistent with those in the International GBS Outcome Study (IGOS) cohort. We provided an overall picture of the present clinical status of GBS in China and summarized the global research progress of GBS, aiming to further understand the characteristics of GBS and improve the future work of GBS worldwide, especially in countries with the middle and low incomes.

Surveillance of COVID-19 vaccine safety among elderly persons aged 65 years and older

BACKGROUND

Monitoring safety outcomes following COVID-19 vaccination is critical for understanding vaccine safety especially when used in key populations such as elderly persons age 65 years and older who can benefit greatly from vaccination. We present new findings from a nationally representative early warning system that may expand the safety knowledge base to further public trust and inform decision making on vaccine safety by government agencies, healthcare providers, interested stakeholders, and the public.

METHODS

We evaluated 14 outcomes of interest following COVID-19 vaccination using the US Centers for Medicare & Medicaid Services (CMS) data covering 30,712,101 elderly persons. The CMS data from December 11, 2020 through Jan 15, 2022 included 17,411,342 COVID-19 vaccinees who received a total of 34,639,937 doses. We conducted weekly sequential testing and generated rate ratios (RR) of observed outcome rates compared to historical (or expected) rates prior to COVID-19 vaccination.

FINDINGS

Four outcomes met the threshold for a statistical signal following BNT162b2 vaccination including pulmonary embolism (PE; RR = 1.54), acute myocardial infarction (AMI; RR = 1.42), disseminated intravascular coagulation (DIC; RR = 1.91), and immune thrombocytopenia (ITP; RR = 1.44). After further evaluation, only the RR for PE still met the statistical threshold for a signal; however, the RRs for AMI, DIC, and ITP no longer did. No statistical signals were identified following vaccination with either the mRNA-1273 or Ad26 COV2.S vaccines.

INTERPRETATION

This early warning system is the first to identify temporal associations for PE, AMI, DIC, and ITP following BNT162b2 vaccination in the elderly. Because an early warning system does not prove that the vaccines cause these outcomes, more robust epidemiologic studies with adjustment for confounding, including age and nursing home residency, are underway to further evaluate these signals. FDA strongly believes the potential benefits of COVID-19 vaccination outweigh the potential risks of COVID-19 infection.

Postmarketing safety surveillance of quadrivalent recombinant influenza vaccine: Reports to the vaccine adverse event reporting system

On October 7, 2016, the Food and Drug Administration approved recombinant hemagglutinin quadrivalent influenza vaccine (RIV4) (Spodoptera frugiperda cell line; Flublok Quadrivalent) for active immunization for the prevention of influenza disease in individuals 18 years of age and older. Clinical trials did not reveal any major differences in adverse events or serious adverse events following Flublok Quadrivalent versus standard-dose quadrivalent inactivated influenza vaccine. To improve our understanding of the safety profile of this vaccine, we reviewed and summarized adverse event reports after Flublok Quadrivalent administration to the Vaccine Adverse Event Reporting System (VAERS). Through June 30, 2020, VAERS received 849 reports after RIV4 vaccination. The vast majority (810; 95%) were non-serious. Among serious events, there were 10 cases of Guillain-Barré syndrome, including 5 people who required mechanical ventilation and 2 people who died. Many allergic reactions were reported as non-serious, but required interventions to treat a life-threatening event, e.g., epinephrine, nebulizers, albuterol, glucocorticoids, and supplemental oxygen. Two people experienced a positive rechallenge (i.e., allergic reactions after repeated vaccination with RIV4), including a person who-despite premedication with antihistamines-developed respiratory difficulties, required epinephrine, and was transported to the emergency department. The occurrence of anaphylaxis and other allergic reactions in some individuals may reflect an underlying predisposition to atopy that may manifest itself after an exposure to any drug or vaccine, and does not necessarily suggest that Flublok Quadrivalent is particularly allergenic. Postmarketing safety surveillance will continue to be vital for understanding the benefits and risks of quadrivalent recombinant influenza vaccine.

Guillain-Barré Syndrome After High-Dose Influenza Vaccine Administration in the United States, 2018-2019 Season

BACKGROUND

The Vaccine Safety Datalink (VSD) identified a statistical signal for an increased risk of Guillain-Barré syndrome (GBS) in days 1-42 after 2018-2019 high-dose influenza vaccine (IIV3-HD) administration. We evaluated the signal using Medicare.

METHODS

We conducted early- and end-of-season claims-based self-controlled risk interval analyses among Medicare beneficiaries ages ≥65 years, using days 8-21 and 1-42 postvaccination as risk windows and days 43-84 as control window. The VSD conducted chart-confirmed analyses.

RESULTS

Among 7 453 690 IIV3-HD vaccinations, we did not detect a statistically significant increased GBS risk for either the 8- to 21-day (odds ratio [OR], 1.85; 95% confidence interval [CI], 0.99-3.44) or 1- to 42-day (OR, 1.31; 95% CI, 0.78-2.18) risk windows. The findings from the end-of-season analyses were fully consistent with the early-season analyses for both the 8- to 21-day (OR, 1.64; 95% CI, 0.92-2.91) and 1- to 42-day (OR, 1.12; 95% CI, 0.70-1.79) risk windows. The VSD's chart-confirmed analysis, involving 646 996 IIV3-HD vaccinations, with 1 case each in the risk and control windows, yielded a relative risk of 1.00 (95% CI, 0.06-15.99).

CONCLUSIONS

The Medicare analyses did not exclude an association between IIV3-HD and GBS, but it determined that, if such a risk existed, it was similar in magnitude to prior seasons. Chart-confirmed VSD results did not confirm an increased risk of GBS.

Vaccine Safety

The details of vaccine development, licensing, and monitoring have never been more important and relevant to the health care conversation in the United States. The potential exists for a preventive medicine such as a vaccine to cause harm, and physicians and patients need to understand the real balance of risks and benefits of immunization. Vaccines given in the United States undergo rigorous testing before licensure as well as extensive postlicensure safety monitoring.

Comparison of alpha-spending plans for near real-time monitoring for Guillain-Barré Syndrome after influenza vaccination during the 2010/11 influenza season

BACKGROUND

Near real-time surveillance of the influenza vaccine, which is administered to a large proportion of the US population every year, is essential to ensure safety of the vaccine. For efficient near real-time surveillance, it is key to select appropriate parameters such as monitoring start date, number of interim tests and a scheme for spending a pre-defined total alpha across the entire influenza season. Guillain-Barré Syndrome, shown to be associated with the 1976 influenza vaccine, is used to evaluate how choices of these parameters can affect whether or not a signal is detected and the time to signal. FDA has been monitoring for the risk of GBS after influenza vaccination for every influenza season since 2008.

METHODS

Using Medicare administrative data and the Updating Sequential Probability Ratio Test methodology to account for claims delay, we evaluated a number of different alpha-spending plans by varying several parameters.

RESULTS

For relative risks of 5 or greater, almost all alpha-spending plans have 100% power; however, for relative risks of 1.5 or lower, the constant and O'Brien-Fleming plans have increasingly more power. For RRs of 1.5 and greater, the Pocock plan signals earliest but would not signal at a RR of 1.25, as observed in prior influenza seasons. There were no remarkable differences across the different plans in regards to monitoring start dates defined by the number of vaccinations; reducing the number of interim tests improves performance only marginally.

CONCLUSIONS

A constant alpha-spending plan appears to be robust, in terms of power and time to detect a signal, across a range of these parameters, including alternate monitoring start dates based on either cumulative vaccinations or GBS claims observed, frequency of monitoring, hypothetical relative risks, and vaccine uptake patterns.

Vaccines and the risk of Guillain-Barré syndrome

The role of vaccination in the development of Guillain-Barré syndrome (GBS) is controversial, although cases of GBS have been reported following a wide range of vaccines. A nested case-control study was conducted between January 2011 and December 2015 in three Chinese cities. Four controls were matched to a case by gender, age, address and index date. An independent expert committee validated the diagnoses of cases and controls according to the Brighton Collaboration GBS case definition. Data on vaccinations were obtained from computerized vaccination records. Causal relations were assessed by conditional logistic regression. 1056 cases of GBS and 4312 controls were included in the analyses. Among paediatric and adult population, adjusted ORs for GBS occurrence within 180 days following vaccination were 0.94 (95% CI 0.54-1.62) and 1.09 (95% CI 0.88-1.32), respectively. No increased risk of GBS was detected for vaccination against hepatitis B, influenza, hepatitis A, varicella, rabies, polio(live), diphtheria, pertuss(acellular), tetanusis, measles, mumps, rubella, Japanese Encephalitis, and meningitis vaccines. Adjusted ORs for the recurrence of GBS after vaccination among paediatric and adult population were 0.85 (95% CI 0.07-9.50) and 1.18 (95% CI 0.49-2.65), respectively. In this large retrospective study, we did not find evidence of an increased risk of GBS and its recurrence among either paediatric (≤ 18 years) or adult (> 18 years) individuals within the 180 days following vaccinations of any kind, including influenza vaccination.

Guillain-Barré syndrome and antecedent cytomegalovirus infection, USA 2009-2015

OBJECTIVE

To describe incidence and clinical characteristics of cases of Guillain-Barré syndrome (GBS) in the USA during 2009-2015, and characteristics of GBS cases with antecedent cytomegalovirus (CMV) infection among persons with employer-sponsored insurance.

METHODS

We analyzed medical claims from IBM Watson MarketScan® databases. GBS patients were defined as enrollees with an inpatient claim with GBS as the principal diagnosis code, based on ICD-9 or ICD-10, and ≥ 1 claim for lumbar puncture or EMG/nerve conduction study. We assessed intensive care unit (ICU) hospitalization, intubation, dysautonomia, and death. We also assessed selected infectious illness within 60 days prior to the first GBS-coded inpatient claim.

RESULTS

We identified 3486 GBS patients; annual incidence was 1.0-1.2/100,000 persons during 2009-2015. GBS incidence was higher in males (1.2/100,000) than in females (0.9/100,000) (p = 0.006) and increased with age, from 0.4/100,000 in persons 0-17 years old to 2.1/100,000 in persons ≥ 65 years old (p < 0.001). Half of GBS patients were hospitalized in the ICU, 8% were intubated, 2% developed dysautonomia, and 1% died. Half had a claim for antecedent illness, but only 125 (3.5%) had a claim for specific infectious pathogens. The mean age among 18 GBS patients with antecedent CMV infection was 39 years versus 47 years among those without antecedent  CMV infection (p = 0.038).

CONCLUSIONS

Incidence of GBS using a large national claims database was comparable to that reported in the literature, but cases appeared to be less severe. Half of GBS patients reported prior infectious illness, but only a minority had a specific pathogen identified.

Surveillance for Guillain-Barré syndrome after 2015-2016 and 2016-2017 influenza vaccination of Medicare beneficiaries

BACKGROUND

Guillain-Barré syndrome (GBS) is a serious acute demyelinating disease, an increased risk of which was found after the 1976 swine flu vaccinations. The U.S. Food and Drug Administration, in collaboration with the Centers for Medicare & Medicaid Services, has been conducting active surveillance for GBS after influenza vaccinations of Medicare Fee-For-Service beneficiaries since 2009.

METHODS

We conducted active surveillance for GBS claims in the 2015-2016 and 2016-2017 influenza seasons using the Updating Sequential Probability Ratio Test (USPRT) to monitor for signals of GBS risk. We performed self-controlled risk interval (SCRI) analyses at the end of both seasons, including chart confirmation in the 2015-2016 season, to estimate the odds ratio of GBS risk. We used 1-42 and 8-21 days post-vaccination as primary and secondary risk windows, respectively, and 43-84 days post-vaccination as the control window.

RESULTS

Over 13 million beneficiaries were vaccinated in each season. USPRT found a low magnitude signal for GBS in both seasons. SCRI analyses did not find excess GBS risk following any influenza vaccine for days 1-42 post-vaccination in either season. In the 2015-2016 season, for the 8-21 day window, our chart-confirmation showed an attributable GBS risk of 0.87 (95% CI: 0.16, 1.49) and 1.68 (95% CI: 0.69, 2.41) cases per million vaccinees after all seasonal and high dose (HD) vaccines, respectively, an elevated GBS risk for beneficiaries aged ≥75 years following all seasonal vaccines (OR: 2.25; 95% CI: 1.15, 4.39) and HD vaccine (OR: 3.67, 95% CI: 1.52, 8.85), and an elevated GBS risk for males who received seasonal vaccines (OR: 2.18; 95% CI: 1.15, 4.15) and HD vaccine (OR: 3.33; 95% CI: 1.35, 8.20). The finding of elevated GBS risk with advancing age and in males is consistent with literature; however, a distinction between HD and SD was a new finding. In the 2016-17 season, for the 8-21 day window, attributed cases showed an attributable GBS risk of 0.87 (95% CI: 0.03, 1.61) and 1.11 (95% CI: 0.00, 2.01) cases per million vaccinees after all seasonal and HD vaccines, respectively. We found no excess GBS risk for standard dose vaccines in the 8-21 day window in either season.

CONCLUSIONS

Our primary analysis finding of no excess GBS risk during both seasons was reassuring. The slightly elevated GBS risk, although in the expected range, in the 8-21 day window after all seasonal and high dose vaccines, but not after standard dose vaccines is hypothesis-generating because the difference may be due to vaccine factors such as antigen amount or strains in various seasons or due to host factors.

Use of routinely collected electronic healthcare data for postlicensure vaccine safety signal detection: a systematic review

Background

Concerns regarding adverse events following vaccination (AEFIs) are a key challenge for public confidence in vaccination. Robust postlicensure vaccine safety monitoring remains critical to detect adverse events, including those not identified in prelicensure studies, and to ensure public safety and public confidence in vaccination. We summarise the literature examined AEFI signal detection using electronic healthcare data, regarding data sources, methodological approach and statistical analysis techniques used.

Methods

We performed a systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Five databases (PubMed/Medline, EMBASE, CINAHL, the Cochrane Library and Web of Science) were searched for studies on AEFIs monitoring published up to 25 September 2017. Studies were appraised for methodological quality, and results were synthesised narratively.

Result

We included 47 articles describing AEFI signal detection using electronic healthcare data. All studies involved linked diagnostic healthcare data, from the emergency department, inpatient and outpatient setting and immunisation records. Statistical analysis methodologies used included non-sequential analysis in 33 studies, group sequential analysis in two studies and 12 studies used continuous sequential analysis. Partially elapsed risk window and data accrual lags were the most cited barriers to monitor AEFIs in near real-time.

Conclusion

Routinely collected electronic healthcare data are increasingly used to detect AEFI signals in near real-time. Further research is required to check the utility of non-coded complaints and encounters, such as telephone medical helpline calls, to enhance AEFI signal detection.

Trial registration number

CRD42017072741.

A simulation study of the statistical power and signaling characteristics of an early season sequential test for influenza vaccine safety

PURPOSE

The US Food and Drug Administration monitors the risk of Guillain-Barré syndrome (GBS) following influenza vaccination using several data sources including Medicare. In the 2017 to 2018 season, we transitioned our near real-time surveillance in Medicare to more effectively detect large GBS risk increases early in the season while avoiding false positives.

METHODS

We conducted a simulation study examining the ability of the updating sequential probability ratio test (USPRT) to detect substantially elevated GBS risk in the 8- to 21-day postvaccination versus 5× to 30× the historical rate. We varied the first testing week (weeks 5-8) and the null rate (1×-3×) and evaluated power. We estimated signal probability and the risk ratio (RR) after signaling when high-risk seasons were rare.

RESULTS

Applying fixed alternatives, we found >80% power to detect a risk 30× the historical rate in week 5 for the 1× null and in week 6 for the 1.5× to 3× nulls. Nearly all testing schedules had >80% power for a 5× risk by week 11. To test the robustness of USPRT, we further simulated seasons where 1% were true high-risk seasons. Using a 1× null led to 10% of seasons signaling by week 11 (median RR approximately 1.4), which decreased to approximately 1% with the ≥2.5× null (median RR approximately 16.0).

CONCLUSIONS

On the basis of the results from this simulation and subsequent consultations with experts and stakeholders, we specified USPRT to test continuously from weeks 7 to 11 using the null hypothesis that the observed GBS rate was 2.5× the historical rate. This helped improve the ability of USPRT to provide early detection of GBS risk following influenza vaccination as part of a multilayered system of surveillance.

Surveillance for Guillain-Barré syndrome after influenza vaccination among U.S. Medicare beneficiaries during the 2017-2018 season

BACKGROUND

The U.S. Food and Drug Administration and the Centers for Medicare & Medicaid Services have been actively monitoring the risk of Guillain-Barré syndrome (GBS) following influenza vaccination among Fee-for-Service (FFS) Medicare beneficiaries every season since 2008. We present our evaluation of the GBS risk following influenza vaccinations during the 2017-2018 season.

METHODS

We implemented a multilayered approach to active safety surveillance that included near real-time surveillance early in the season, comparing GBS rates post-vaccination during the 2017-2018 season with rates from five prior seasons using the Updating Sequential Probability Ratio Test (USPRT), and end-of-season self-controlled risk interval (SCRI) analyses.

RESULTS

We identified approximately 16 million influenza vaccinations. The near real-time surveillance did not signal for a potential 2.5-fold increased GBS risk either in days 8-21 or 1-42 post-influenza vaccination. In the SCRI analyses, we did not detect statistically significant increased GBS risks among influenza-vaccinated Medicare beneficiaries ≥65 years for either the 8-21 or 1-42-day risk windows for all seasonal vaccines combined, high-dose vaccine, or standard-dose vaccines; we did detect an increased GBS risk in days 8-21 post-vaccination for individuals vaccinated with the adjuvanted vaccine (OR: 3.75; 95% CI: 1.01, 13.96), although this finding was not statistically significant after multiplicity adjustment (p = 0.146).

CONCLUSIONS

Our multilayered surveillance approach-which allows for early detection of elevated GBS risk and provides reliable end-of-season SCRI estimates of effect size-did not identify an increased GBS risk following 2017-2018 influenza vaccinations. The slightly increased GBS risk with the adjuvanted vaccine, which was not statistically significant following multiplicity adjustment, is consistent with the package inserts of all U.S.-licensed influenza vaccines, which warn of a potential low increased GBS risk. The benefits of influenza vaccines in preventing morbidity and mortality heavily outweigh this potential risk.

Systematic review of factors associated with the development of Guillain-Barré syndrome 2007-2017: what has changed?

OBJECTIVE

The objective of this study was to describe the factors associated with the development of Guillain-Barré syndrome, both infectious and non-infectious, during and after the A(H1N1) influenza pandemic in 2009 and the recent Zika virus epidemic in the Americas.

METHOD

Systematic review of literature on factors associated with the development of the Guillain-Barré syndrome published between 2007 and 2017 listed in EBSCO, MEDLINE and LILACS databases. The quality of the studies was evaluated using the Newcastle Ottawa Scale.

RESULTS

Thirty-four articles met inclusion criteria and were selected for analysis. Their quality was considered good in relation to most of the items evaluated. Many aetiological agents had the results of association with Guillain-Barré syndrome, among them Campylobacter jejuni, influenza vaccine - both pandemic and seasonal vaccines, respiratory infection, gastrointestinal infection among others. The aetiological agents found are, in most part, the same reported prior to the study period. The association with surgeries, chikungunya virus (CHIKV), Zika virus and quadrivalent human papillomavirus vaccine stand out as new aetiological agents in the list of the various possible agents that trigger Guillain-Barré syndrome reported in the study period. There were no Brazilian studies identified during this period.

CONCLUSIONS

The results of the review reaffirmed C. jejuni as the major trigger of GBS, whereas the association of influenza vaccines and GBS is less clear; Zika virus infection in association with GBS was found in only one study.

Influenza vaccines: Evaluation of the safety profile

The safety of vaccines is a critical factor in maintaining public trust in national vaccination programs. Vaccines are recommended for children, adults and elderly subjects and have to meet higher safety standards, since they are administered to healthy subjects, mainly healthy children. Although vaccines are strictly monitored before authorization, the possibility of adverse events and/or rare adverse events cannot be totally eliminated. Two main types of influenza vaccines are currently available: parenteral inactivated influenza vaccines and intranasal live attenuated vaccines. Both display a good safety profile in adults and children. However, they can cause adverse events and/or rare adverse events, some of which are more prevalent in children, while others with a higher prevalence in adults. The aim of this review is to provide an overview of influenza vaccine safety according to target groups, vaccine types and production methods.

Real world big data for clinical research and drug development

The objective of this paper is to identify the extent to which real world data (RWD) is being utilized, or could be utilized, at scale in drug development. Through screening peer-reviewed literature, we have cited specific examples where RWD can be used for biomarker discovery or validation, gaining a new understanding of a disease or disease associations, discovering new markers for patient stratification and targeted therapies, new markers for identifying persons with a disease, and pharmacovigilance. None of the papers meeting our criteria was specifically geared toward novel targets or indications in the biopharmaceutical sector; the majority were focused on the area of public health, often sponsored by universities, insurance providers or in combination with public health bodies such as national insurers. The field is still in an early phase of practical application, and is being harnessed broadly where it serves the most direct need in public health applications in early, rare and novel disease incidents. However, these exemplars provide a valuable contribution to insights on the use of RWD to create novel, faster and less invasive approaches to advance disease understanding and biomarker discovery. We believe that pharma needs to invest in making better use of Electronic Health Records and the need for more precompetitive collaboration to grow the scale of this 'big denominator' capability, especially given the needs of precision medicine research.

Continuous Post-Market Sequential Safety Surveillance with Minimum Events to Signal

The CDC Vaccine Safety Datalink project has pioneered the use of near real-time post-market vaccine safety surveillance for the rapid detection of adverse events. Doing weekly analyses, continuous sequential methods are used, allowing investigators to evaluate the data near-continuously while still maintaining the correct overall alpha level. With continuous sequential monitoring, the null hypothesis may be rejected after only one or two adverse events are observed. In this paper, we explore continuous sequential monitoring when we do not allow the null to be rejected until a minimum number of observed events have occurred. We also evaluate continuous sequential analysis with a delayed start until a certain sample size has been attained. Tables with exact critical values, statistical power and the average times to signal are provided. We show that, with the first option, it is possible to both increase the power and reduce the expected time to signal, while keeping the alpha level the same. The second option is only useful if the start of the surveillance is delayed for logistical reasons, when there is a group of data available at the first analysis, followed by continuous or near-continuous monitoring thereafter.

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.

Prevention and Control of Seasonal Influenza with Vaccines

This report updates the 2015-16 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines (Grohskopf LA, Sokolow LZ, Olsen SJ, Bresee JS, Broder KR, Karron RA. Prevention and control of influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices, United States, 2015-16 influenza season. MMWR Morb Mortal Wkly Rep 2015;64:818-25). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. For the 2016-17 influenza season, inactivated influenza vaccines (IIVs) will be available in both trivalent (IIV3) and quadrivalent (IIV4) formulations. Recombinant influenza vaccine (RIV) will be available in a trivalent formulation (RIV3). In light of concerns regarding low effectiveness against influenza A(H1N1)pdm09 in the United States during the 2013-14 and 2015-16 seasons, for the 2016-17 season, ACIP makes the interim recommendation that live attenuated influenza vaccine (LAIV4) should not be used. Vaccine virus strains included in the 2016-17 U.S. trivalent influenza vaccines will be an A/California/7/2009 (H1N1)-like virus, an A/Hong Kong/4801/2014 (H3N2)-like virus, and a B/Brisbane/60/2008-like virus (Victoria lineage). Quadrivalent vaccines will include an additional influenza B virus strain, a B/Phuket/3073/2013-like virus (Yamagata lineage).Recommendations for use of different vaccine types and specific populations are discussed. A licensed, age-appropriate vaccine should be used. No preferential recommendation is made for one influenza vaccine product over another for persons for whom more than one licensed, recommended product is otherwise appropriate. This information is intended for vaccination providers, immunization program personnel, and public health personnel. Information in this report reflects discussions during public meetings of ACIP held on October 21, 2015; February 24, 2016; and June 22, 2016. These recommendations apply to all licensed influenza vaccines used within Food and Drug Administration-licensed indications, including those licensed after the publication date of this report. Updates and other information are available at CDC's influenza website (http://www.cdc.gov/flu). Vaccination and health care providers should check CDC's influenza website periodically for additional information.

Adverse events following pandemic influenza A (H1N1) 2009 monovalent and seasonal influenza vaccinations during the 2009-2010 season in the active component U.S. military and civilians aged 17-44years reported to the Vaccine Adverse Event Reporting System

BACKGROUND

No comparative review of Vaccine Adverse Event Reporting System (VAERS) submissions following pandemic influenza A (H1N1) 2009 and seasonal influenza vaccinations during the pandemic season among U.S. military personnel has been published.

METHODS

We compared military vs. civilian adverse event reporting rates. Adverse events (AEs) following vaccination were identified from VAERS for adults aged 17-44years after pandemic (monovalent influenza [MIV], and seasonal (trivalent inactivated influenza [IIV3], live attenuated influenza [LAIV3]) vaccines. Military vaccination coverage was provided by the Department of Defense's Defense Medical Surveillance System. Civilian vaccination coverage was estimated using data from the National 2009 H1N1 Flu Survey and the Behavioral Risk Factor Surveillance System survey.

RESULTS

Vaccination coverage was more than four times higher for MIV and more than twenty times higher for LAIV3 in the military than in the civilian population. The reporting rate of serious AE reports following MIV in service personnel (1.19 per 100,000) was about half that reported by the civilian population (2.45 per 100,000). Conversely, the rate of serious AE reports following LAIV3 among service personnel (1.32 per 100,000) was more than twice that of the civilian population. Although fewer military AEs following MIV were reported overall, the rate of Guillain-Barré Syndrome (GBS) (4.01 per million) was four times greater than that in the civilian population. (1.04 per million).

CONCLUSIONS

Despite higher vaccination coverage in service personnel, the rate of serious AEs following MIV was about half that in civilians. The rate of GBS reported following MIV was higher in the military.

Guillain-Barré syndrome following the 2009 pandemic monovalent and seasonal trivalent influenza vaccination campaigns in Spain from 2009 to 2011: outcomes from active surveillance by a neurologist network, and records from a country-wide hospital discharge database

Background

Studies have shown a slight excess risk in Guillain-Barré syndrome (GBS) incidence associated with A(H1N1)pdm09 vaccination campaign and seasonal trivalent influenza vaccine immunisations in 2009–2010. We aimed to assess the incidence of GBS as a potential adverse effect of A(H1N1)pdm09 vaccination.

Methods

A neurologist-led network, active at the neurology departments of ten general hospitals serving an adult population of 4.68 million, conducted GBS surveillance in Spain in 2009–2011. The network, established in 1996, carried out a retrospective and a prospective study to estimate monthly alarm thresholds in GBS incidence and tested them in 1998–1999 in a pilot study. Such incidence thresholds additionally to observation of GBS cases with immunisation antecedent in the 42 days prior to clinical onset were taken as alarm signals for 2009–2011, since November 2009 onwards. For purpose of surveillance, in 2009 we updated both the available centres and the populations served by the network. We also did a retrospective countrywide review of hospital-discharged patients having ICD-9-CM code 357.0 (acute infective polyneuritis) as their principal diagnosis from January 2009 to December 2011.

Results

Among 141 confirmed of 148 notified cases of GBS or Miller-Fisher syndrome, Brighton 1–2 criteria in 96 %, not a single patient was identified with clinical onset during the 42-day time interval following A(H1N1)pdm09 vaccination. In contrast, seven cases were seen during a similar period after seasonal campaigns. Monthly incidence figures did not, however, exceed the upper 95 % CI limit of expected incidence. A retrospective countrywide review of the registry of hospital-discharged patients having ICD-9-CM code 357.0 (acute infective polyneuritis) as their principal diagnosis did not suggest higher admission rates in critical months across the period December 2009-February 2010.

Conclusions

Despite limited power and underlying reporting bias in 2010–2011, an increase in GBS incidence over background GBS, associated with A(H1N1)pdm09 monovalent or trivalent influenza immunisations, appears unlikely.

Near real-time vaccine safety surveillance using electronic health records-a systematic review of the application of statistical methods

PURPOSE

Pre-licensure studies have limited ability to detect rare adverse events (AEs) to vaccines, requiring timely post-licensure studies. With the increasing availability of electronic health records (EHR) near real-time vaccine safety surveillance using these data has emerged as an option. We reviewed methods currently used to inform development of similar systems for countries considering their introduction.

METHODS

Medline, EMBASE and Web of Science were searched, with additional searches of conference abstract books. Questionnaires were sent to organizations worldwide to ascertain unpublished studies. Eligible studies used EHR and regularly assessed pre-specified AE to vaccine(s). Key features of studies were compared descriptively.

RESULTS

From 2779 studies, 31 were included from the USA (23), UK (6), and Taiwan and New Zealand (1 each). These were published/conducted between May 2005 and April 2015. Thirty-eight different vaccines were studied, focusing mainly on influenza (47.4%), especially 2009 H1N1 vaccines. Forty-six analytic approaches were used, reflecting frequency of EHR updates and the AE studied. Poisson-based maximized sequential probability ratio test was the most common (43.5%), followed by its binomial (23.9%) and conditional versions (10.9%). Thirty-seven of 49 analyses (75.5%) mentioned control for confounding, using an adjusted expected rate (51.4% of those adjusting), stratification (16.2%) or a combination of a self-controlled design and stratification (13.5%). Guillain-Barré syndrome (11.9%), meningitis/encephalitis/myelitis (11.9%) and seizures (10.8%) were studied most often.

CONCLUSIONS

Near real-time vaccine safety surveillance using EHR has developed over the past decade but is not yet widely used. As more countries have access to EHR, it will be important that appropriate methods are selected, considering the data available and AE of interest.

Prospective influenza vaccine safety surveillance using fresh data in the Sentinel System

Purpose

To develop the infrastructure to conduct timely active surveillance for safety of influenza vaccines and other medical countermeasures in the Sentinel System (formerly the Mini‐Sentinel Pilot), a Food and Drug Administration‐sponsored national surveillance system that typically relies on data that are mature, settled, and updated quarterly.

Methods

Three Data Partners provided their earliest available (“fresh”) cumulative claims data on influenza vaccination and health outcomes 3–4 times on a staggered basis during the 2013–2014 influenza season, collectively producing 10 data updates. We monitored anaphylaxis in the entire population using a cohort design and seizures in children ≤4 years of age using both a self‐controlled risk interval design (primary) and a cohort design (secondary). After each data update, we conducted sequential analysis for inactivated (IIV) and live (LAIV) influenza vaccines using the Maximized Sequential Probability Ratio Test, adjusting for data‐lag.

Results

Most of the 10 sequential analyses were conducted within 6 weeks of the last care‐date in the cumulative dataset. A total of 6 682 336 doses of IIV and 782 125 doses of LAIV were captured. The primary analyses did not identify any statistical signals following IIV or LAIV. In secondary analysis, the risk of seizures was higher following concomitant IIV and PCV13 than historically after IIV in 6‐ to 23‐month‐olds (relative risk = 2.7), which requires further investigation.

Conclusions

The Sentinel System can implement a sequential analysis system that uses fresh data for medical product safety surveillance. Active surveillance using sequential analysis of fresh data holds promise for detecting clinically significant health risks early. Limitations of employing fresh data for surveillance include cost and the need for careful scrutiny of signals. © 2015 The Authors. Pharmacoepidemiology and Drug Safety Published by John Wiley & Sons Ltd.

Medicare claims versus beneficiary self-report for influenza vaccination surveillance

BACKGROUND

Although self-reported influenza vaccination status is routinely used in surveillance to estimate influenza vaccine coverage, Medicare data are becoming a promising resource for influenza surveillance to inform vaccination program management and planning.

PURPOSE

To evaluate the concordance between self-reported influenza vaccination and influenza vaccination claims among Medicare beneficiaries.

METHODS

This study compared influenza vaccination based upon Medicare claims and self-report among a sample of Medicare beneficiaries (N=9,378) from the 2011 Medicare Current Beneficiary Survey, which was the most recent year of data at the time of analysis (summer 2013). Sensitivity, specificity, positive predictive value, and negative predictive value were calculated using self-reported data as the referent standard. Logistic regression was used to compute the marginal mean proportions for whether a Medicare influenza vaccination claim was present among beneficiaries who reported receiving the vaccination.

RESULTS

Influenza vaccination was higher for self-report (69.4%) than Medicare claims (48.3%). For Medicare claims, sensitivity=67.5%, specificity=96.3%, positive predictive value=97.6%, and negative predictive value=56.7%. Among beneficiaries reporting receiving an influenza vaccination, the percentage of beneficiaries with a vaccination claim was lower for beneficiaries who were aged <65 years, male, non-Hispanic black or Hispanic, and had less than a college education.

CONCLUSIONS

The classification of influenza vaccination status for Medicare beneficiaries can differ based upon survey and claims. To improve Medicare claims-based surveillance studies, further research is needed to determine the sources of discordance in self-reported and Medicare claims data, specifically for sensitivity and negative predictive value.

Comparative effectiveness of high-dose versus standard-dose influenza vaccines in US residents aged 65 years and older from 2012 to 2013 using Medicare data: a retrospective cohort analysis

BACKGROUND

A high-dose trivalent inactivated influenza vaccine was licensed in 2009 by the US Food and Drug Administration (FDA) on the basis of serological criteria. We sought to establish whether high-dose inactivated influenza vaccine was more effective for prevention of influenza-related visits and hospital admissions in US Medicare beneficiaries than was standard-dose inactivated influenza vaccine.

METHODS

In this retrospective cohort study, we identified Medicare beneficiaries aged 65 years and older who received high-dose or standard-dose inactivated influenza vaccines from community pharmacies that offered both vaccines during the 2012-13 influenza season. Outcomes were defined with billing codes on Medicare claims. The primary outcome was probable influenza infection, defined by receipt of a rapid influenza test followed by dispensing of the neuraminidase inhibitor oseltamivir. The secondary outcome was a hospital or emergency department visit, listing a Medicare billing code for influenza. We estimated relative vaccine effectiveness by comparing outcome rates in Medicare beneficiaries during periods of high influenza circulation. Univariate and multivariate Poisson regression models were used for analyses.

FINDINGS

Between Aug 1, 2012 and Jan 31, 2013, we studied 929,730 recipients of high-dose vaccine and 1,615,545 recipients of standard-dose vaccine. Participants enrolled in each cohort were well balanced with respect to age and presence of underlying medical disorders. The high-dose vaccine (1·30 outcomes per 10,000 person-weeks) was 22% (95% CI 15-29) more effective than the standard-dose vaccine (1·01 outcomes per 10,000 person-weeks) for prevention of probable influenza infections (rapid influenza test followed by oseltamivir treatment) and 22% (95% CI 16-27%) more effective for prevention of influenza hospital admissions (0·86 outcomes per 10,000 person-weeks in the high-dose cohort vs 1·10 outcomes per 10,000 person-weeks in the standard-dose cohort).

INTERPRETATION

Our retrospective cohort study in US Medicare beneficiaries shows that, in people 65 years of age and older, high-dose inactivated influenza vaccine was significantly more effective than standard-dose vaccine in prevention of influenza-related medical encounters. Additionally, the large population in our study enabled us to show, for the first time, a significant reduction in influenza-related hospital admissions in high-dose compared to standard-dose vaccine recipients, an outcome not shown in randomised studies. These results provide important new information to be considered by policy makers recommending influenza vaccinations for elderly people.

FUNDING

FDA and the office of the Assistant Secretary of Planning and Evaluation.

Dialysis care and death following Hurricane Sandy

BACKGROUND

Hurricane Sandy affected access to critical health care infrastructure. Patients with end-stage renal disease (ESRD) historically have experienced problems accessing care and adverse outcomes during disasters.

STUDY DESIGN

Retrospective cohort study with 2 comparison groups.

SETTING & PARTICIPANTS

Using Centers for Medicare & Medicaid Services claims data, we assessed the frequency of early dialysis, emergency department (ED) visits, hospitalizations, and 30-day mortality for patients with ESRD in Sandy-affected areas (study group) and 2 comparison groups: (1) patients with ESRD living in states unaffected by Sandy during the same period and (2) patients with ESRD living in the Sandy-affected region a year prior to the hurricane (October 1, 2011, through October 30, 2011).

FACTOR

Regional variation in dialysis care patterns and mortality for patients with ESRD in New York City and the State of New Jersey.

MEASUREMENTS

Frequency of early dialysis, ED visits, hospitalizations, and 30-day mortality.

RESULTS

Of 13,264 study patients, 59% received early dialysis in 70% of the New York City and New Jersey dialysis facilities. The ED visit rate was 4.1% for the study group compared with 2.6% and 1.7%, respectively, for comparison groups 1 and 2 (both P<0.001). The hospitalization rate for the study group also was significantly higher than that in either comparison group (4.5% vs 3.2% and 3.8%, respectively; P<0.001 and P<0.003). 23% of study group patients who visited the ED received dialysis in the ED compared with 9.3% and 6.3% in comparison groups 1 and 2, respectively (both P<0.001). The 30-day mortality rate for the study group was slightly higher than that for either comparison group (1.83% vs 1.47% and 1.60%, respectively; P<0.001 and P=0.1).

LIMITATIONS

Lack of facility level damage and disaster-induced power outage severity data.

CONCLUSIONS

Nearly half the study group patients received early dialysis prior to Sandy's landfall. Poststorm increases in ED visits, hospitalizations, and 30-day mortality were found in the study group, but not in the comparison groups.

A global regulatory science agenda for vaccines

The Decade of Vaccines Collaboration and development of the Global Vaccine Action Plan provides a catalyst and unique opportunity for regulators worldwide to develop and propose a global regulatory science agenda for vaccines. Regulatory oversight is critical to allow access to vaccines that are safe, effective, and of assured quality. Methods used by regulators need to constantly evolve so that scientific and technological advances are applied to address challenges such as new products and technologies, and also to provide an increased understanding of benefits and risks of existing products. Regulatory science builds on high-quality basic research, and encompasses at least two broad categories. First, there is laboratory-based regulatory science. Illustrative examples include development of correlates of immunity; or correlates of safety; or of improved product characterization and potency assays. Included in such science would be tools to standardize assays used for regulatory purposes. Second, there is science to develop regulatory processes. Illustrative examples include adaptive clinical trial designs; or tools to analyze the benefit-risk decision-making process of regulators; or novel pharmacovigilance methodologies. Included in such science would be initiatives to standardize regulatory processes (e.g., definitions of terms for adverse events [AEs] following immunization). The aim of a global regulatory science agenda is to transform current national efforts, mainly by well-resourced regulatory agencies, into a coordinated action plan to support global immunization goals. This article provides examples of how regulatory science has, in the past, contributed to improved access to vaccines, and identifies gaps that could be addressed through a global regulatory science agenda. The article also identifies challenges to implementing a regulatory science agenda and proposes strategies and actions to fill these gaps. A global regulatory science agenda will enable regulators, academics, and other stakeholders to converge around transformative actions for innovation in the regulatory process to support global immunization goals.

Infectious and noninfectious triggers in Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is the commonest cause of acquired flaccid paralysis in the world and regarded by many as the prototype for postinfectious autoimmunity. Here the authors consider both infectious and noninfectious triggers of GBS and determine where possible what immunological mechanisms may account for this association. In approximately two-thirds of cases, an infectious trigger is reported in the weeks that lead up to disease onset, indicating that the host's response to infection must play an important role in disease pathogenesis. The most frequently identified bacteria, Campylobacter jejuni, through a process known as molecular mimicry, has been shown to induce cross-reactive anti-ganglioside antibodies, which can lead to the development of axonal-type GBS in some patients. Whether this paradigm can be extended to other infectious organisms or vaccines remains an important area of research and has public health implications. GBS has also been reported rarely in patients with underlying systemic diseases and immunocompromised states and although the exact mechanism is yet to be established, increased susceptibility to known infectious triggers should be considered most likely.

Acute disseminated encephalomyelitis onset: evaluation based on vaccine adverse events reporting systems

OBJECTIVE

To evaluate epidemiological features of post vaccine acute disseminated encephalomyelitis (ADEM) by considering data from different pharmacovigilance surveillance systems.

METHODS

The Vaccine Adverse Event Reporting System (VAERS) database and the EudraVigilance post-authorisation module (EVPM) were searched to identify post vaccine ADEM cases. Epidemiological features including sex and related vaccines were analysed.

RESULTS

We retrieved 205 and 236 ADEM cases from the EVPM and VAERS databases, respectively, of which 404 were considered for epidemiological analysis following verification and causality assessment. Half of the patients had less than 18 years and with a slight male predominance. The time interval from vaccination to ADEM onset was 2-30 days in 61% of the cases. Vaccine against seasonal flu and human papilloma virus vaccine were those most frequently associated with ADEM, accounting for almost 30% of the total cases. Mean number of reports per year between 2005 and 2012 in VAERS database was 40±21.7, decreasing after 2010 mainly because of a reduction of reports associated with human papilloma virus and Diphtheria, Pertussis, Tetanus, Polio and Haemophilus Influentiae type B vaccines.

CONCLUSIONS

This study has a high epidemiological power as it is based on information on adverse events having occurred in over one billion people. It suffers from lack of rigorous case verification due to the weakness intrinsic to the surveillance databases used. At variance with previous reports on a prevalence of ADEM in childhood we demonstrate that it may occur at any age when post vaccination. This study also shows that the diminishing trend in post vaccine ADEM reporting related to Diphtheria, Pertussis, Tetanus, Polio and Haemophilus Influentiae type B and human papilloma virus vaccine groups is most likely not [corrected] due to a decline in vaccine coverage indicative of a reduced attention to this adverse drug reaction.

Acute disseminated encephalomyelitis onset: evaluation based on vaccine adverse events reporting systems

OBJECTIVE

To evaluate epidemiological features of post vaccine acute disseminated encephalomyelitis (ADEM) by considering data from different pharmacovigilance surveillance systems.

METHODS

The Vaccine Adverse Event Reporting System (VAERS) database and the EudraVigilance post-authorisation module (EVPM) were searched to identify post vaccine ADEM cases. Epidemiological features including sex and related vaccines were analysed.

RESULTS

We retrieved 205 and 236 ADEM cases from the EVPM and VAERS databases, respectively, of which 404 were considered for epidemiological analysis following verification and causality assessment. Half of the patients had less than 18 years and with a slight male predominance. The time interval from vaccination to ADEM onset was 2-30 days in 61% of the cases. Vaccine against seasonal flu and human papilloma virus vaccine were those most frequently associated with ADEM, accounting for almost 30% of the total cases. Mean number of reports per year between 2005 and 2012 in VAERS database was 40±21.7, decreasing after 2010 mainly because of a reduction of reports associated with human papilloma virus and Diphtheria, Pertussis, Tetanus, Polio and Haemophilus Influentiae type B vaccines.

CONCLUSIONS

This study has a high epidemiological power as it is based on information on adverse events having occurred in over one billion people. It suffers from lack of rigorous case verification due to the weakness intrinsic to the surveillance databases used. At variance with previous reports on a prevalence of ADEM in childhood we demonstrate that it may occur at any age when post vaccination. This study also shows that the diminishing trend in post vaccine ADEM reporting related to Diphtheria, Pertussis, Tetanus, Polio and Haemophilus Influentiae type B and human papilloma virus vaccine groups is most likely not [corrected] due to a decline in vaccine coverage indicative of a reduced attention to this adverse drug reaction.

Chart-confirmed guillain-barre syndrome after 2009 H1N1 influenza vaccination among the Medicare population, 2009-2010

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

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.

Vaccination of healthy children against seasonal influenza: a European perspective

Despite ample evidence for the great burden that annual influenza epidemics place on children and society in general, few European countries currently recommend influenza vaccination of healthy children of any age. The most frequently cited reasons for reluctance to extend general vaccine recommendations to children include the view that influenza is a mild illness of limited clinical importance, lack of country-specific data on disease burden, uncertainty about the efficacy and safety of influenza vaccines in children and inadequate evidence of cost-effectiveness of vaccinating children. In recent years, several clinical studies have provided new and important information that help address many of these areas of question and concern. In light of this newly available scientific evidence, influenza vaccine recommendations for children should be properly reevaluated in all European countries. Furthermore, to allow for variation in costs and patterns of healthcare delivery between different countries, cost-effectiveness analyses of influenza vaccination of healthy children should be performed in each country or region. Finally, increased efforts should be made to educate both healthcare professionals and the great public about recent findings and advances in the field of pediatric influenza.

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

BACKGROUND

The influenza A (H1N1) 2009 monovalent vaccination programme was the largest mass vaccination initiative in recent US history. Commensurate with the size and scope of the vaccination programme, a project to monitor vaccine adverse events was undertaken, the most comprehensive safety surveillance agenda in the USA to date. The adverse event monitoring project identified an increased risk of Guillain-Barré syndrome after vaccination; however, some individual variability in results was noted. Guillain-Barré syndrome is a rare but serious health disorder in which a person's own immune system damages their nerve cells, causing muscle weakness, sometimes paralysis, and infrequently death. We did a meta-analysis of data from the adverse event monitoring project to ascertain whether influenza A (H1N1) 2009 monovalent inactivated vaccines used in the USA increased the risk of Guillain-Barré syndrome.

METHODS

Data were obtained from six adverse event monitoring systems. About 23 million vaccinated people were included in the analysis. The primary analysis entailed calculation of incidence rate ratios and attributable risks of excess cases of Guillain-Barré syndrome per million vaccinations. We used a self-controlled risk-interval design.

FINDINGS

Influenza A (H1N1) 2009 monovalent inactivated vaccines were associated with a small increased risk of Guillain-Barré syndrome (incidence rate ratio 2·35, 95% CI 1·42-4·01, p=0·0003). This finding translated to about 1·6 excess cases of Guillain-Barré syndrome per million people vaccinated.

INTERPRETATION

The modest risk of Guillain-Barré syndrome attributed to vaccination is consistent with previous estimates of the disorder after seasonal influenza vaccination. A risk of this small magnitude would be difficult to capture during routine seasonal influenza vaccine programmes, which have extensive, but comparatively less, safety monitoring. In view of the morbidity and mortality caused by 2009 H1N1 influenza and the effectiveness of the vaccine, clinicians, policy makers, and those eligible for vaccination should be assured that the benefits of inactivated pandemic vaccines greatly outweigh the risks.

FUNDING

US Federal Government.

Success of program linking data sources to monitor H1N1 vaccine safety points to potential for even broader safety surveillance

In response to the 2009 H1N1 pandemic and subsequent vaccination program, the Department of Health and Human Services and collaborators developed the Post-Licensure Rapid Immunization Safety Monitoring (PRISM) Program as a demonstration project to detect rare adverse events rapidly. The program monitored three million people who had received the H1N1 vaccine by linking data from large private health plans and from public immunization registries that had originally not been designed to share data, and on a larger scale than had been previously attempted. The program generated safety data in two weeks rather than three to six monty 10ths-the standard time frame achievable using health plan data. PRISM substantially contributed to the understanding of the safety of H1N1 vaccines. Its use in the case of H1N1 highlights the necessity of proactive planning, scalable infrastructure, and public-private partnerships in tracking adverse events after vaccination in epidemics. It also illustrates how data could be integrated to produce policy-relevant information for other medical products.