Quadrivalent human papillomavirus vaccination in girls and the risk of autoimmune disorders: the Ontario Grade 8 HPV Vaccine Cohort Study.

BACKGROUND: Despite demonstrated effectiveness in real-world settings, concerns persist regarding the safety of the quadrivalent human papillomavirus (HPV4) vaccine. We sought to assess the risk of autoimmune disorders following HPV4 vaccination among grade 8 girls eligible for Ontario's school-based HPV vaccination program. METHODS: We undertook a population-based retrospective cohort study using Ontario's administrative health and vaccination databases from 2007 to 2013. The self-controlled case series method was used to compare the rate of a composite end point of autoimmune disorders diagnosed during days 7-60 post-vaccination ("exposed" follow-up) to that at any other time ("unexposed"). The analysis was repeated to assess the effect of a history of immune-mediated diseases and time since vaccination. We also conducted an exploratory analysis of individual autoimmune disorders. Rate ratios and 95% confidence intervals (CIs) were estimated using conditional Poisson regression, adjusted for age, seasonality, concomitant vaccinations and infections. RESULTS: The study cohort consisted of 290 939 girls aged 12-17 years who were eligible for vaccination between 2007 and 2013. There was no significant risk for developing an autoimmune disorder following HPV4 vaccination (n = 681; rate ratio 1.12, 95% CI 0.85-1.47), and the association was unchanged by a history of immune-mediated disorders and time since vaccination. Exploratory analyses of individual autoimmune disorders found no significant risks, including for Bell palsy (n = 65; rate ratio 1.73, 95% CI 0.77-3.89), optic neuritis (n = 67; rate ratio 1.57, 95% CI 0.74-3.33) and Graves disease (n = 47; rate ratio 1.55, 95% CI 0.92-2.63). INTERPRETATION: We did not observe an increased risk of autoimmune disorders following HPV4 vaccination among teenaged girls. These findings should reassure parents and health care providers.

Canada's eight-component vaccine safety system: A primer for health care workers.

Concerns about vaccine safety make some parents hesitant about immunization. Health care providers are pivotal in helping parents understand that Canada is a leader in vaccine safety. The present practice point provides an update on the eight components of Canada's vaccine safety system: (1) an evidence-based pre-license review and approval process; (2) strong regulations for manufacturers; (3) independent evidence-based vaccine use recommendations; (4) immunization competency training and standards for health care providers; (5) pharmacovigilance programs to detect and (6) determine causality of adverse events following immunization (AEFIs); (7) a program for vaccine safety and efficacy signal detection; and (8) the Canadian Immunization Research Network's special immunization clinics for children who have experienced serious AEFIs.

Canada's eight-component vaccine safety system: A primer for health care workers.

Concerns about vaccine safety make some parents hesitant about immunization. Health care providers are pivotal in helping parents understand that Canada is a leader in vaccine safety. The present practice point provides an update on the eight components of Canada's vaccine safety system: (1) an evidence-based pre-license review and approval process; (2) strong regulations for manufacturers; (3) independent evidence-based vaccine use recommendations; (4) immunization competency training and standards for health care providers; (5) pharmacovigilance programs to detect and (6) determine causality of adverse events following immunization (AEFIs); (7) a program for vaccine safety and efficacy signal detection; and (8) the Canadian Immunization Research Network's special immunization clinics for children who have experienced serious AEFIs.

Validation of the newly proposed Brighton Collaboration case definition for vaccine-induced immune thrombocytopenia and thrombosis.

Vaccine-induced immune thrombocytopenia and thrombosis (VITT) is a newly recognized syndrome mediated by anti-platelet factor 4 antibodies induced by Covid-19 adenovirus-vectored vaccines including ChAdOx1 nCoV-19 and Ad26.COV2.S. This study validated a proposed Brighton Collaboration case definition for VITT. A data collection form was developed and used to capture the variations in VITT criteria and assess their level of diagnostic certainty from adjudicated positive VITT case datasheets in Germany (n = 71), UK (n = 220), Australia (n = 203), and Taiwan (n = 56). We observed high prevalence of each component of the proposed VITT definition in positive cases (84%-100%), except for the occurrence of thrombosis or thromboembolism criterion in only 34% of VITT cases in Taiwan. The sensitivity of this proposed definition was 100% for Germany and UK, 92% for Australia, and 89% for Taiwan cases. These findings support the validity of this case definition for VITT.

Thrombosis with thrombocytopenia syndrome (TTS) and vaccine-induced immune thrombocytopenia and thrombosis (VITT): Brighton Collaboration case definitions and guidelines for data collection, analysis, and presentation of immunisation safety data.

This is a revision of the online November 2021 Brighton thrombosis with thrombocytopenia syndrome (TTS) case definition and a new Brighton Collaboration case definition for vaccine-induced immune thrombocytopenia and thrombosis (VITT). These case definitions are intended for use in clinical trials and post-licensure pharmacovigilance activities to facilitate safety data comparability across multiple settings. They are not intended to guide clinical management. The case definitions were developed by a group of subject matter and Brighton Collaboration process experts as part of the Coalition for Epidemic Preparedness Innovations (CEPI)-funded Safety Platform for Evaluation of vACcines (SPEAC). The case definitions, each with defined levels of diagnostic certainty, are based on relevant published evidence and expert consensus and are accompanied by specific guidelines for TTS and VITT data collection and analysis. The document underwent peer review by a reference group of vaccine safety stakeholders and haematology experts to ensure case definition useability, applicability and scientific integrity.

Anosmia: Brighton Collaboration case definition and guidelines for data collection, analysis, and presentation of immunization safety data.

This is a Brighton Collaboration case definition of anosmia to be used in the evaluation of adverse events following immunization, and for epidemiologic studies for the assessment of background incidence or hypothesis testing. The case definition was developed by a group of experts convened by the Coalition for Epidemic Preparedness Innovations (CEPI) in the context of active development of SARS-CoV-2 vaccines. The case definition format of the Brighton Collaboration was followed to develop a consensus definition and defined levels of certainty, after an exhaustive review of the literature and expert consultation. The document underwent peer review by the Brighton Collaboration Network and by two expert reviewers prior to submission.

Anaphylaxis: Revision of the Brighton collaboration case definition.

The Brighton Collaboration (BC) has formulated a number of case definitions which have primarily been applied to adverse events of special interest in the context of vaccine safety surveillance. This is a revision of the 2007 BC case definition for anaphylaxis. Recently, the BC definition has been widely used for evaluating reports of suspected anaphylaxis following COVID-19 vaccination. This has led to debate about the performance of the BC definition in comparison with those from the US National Institute of Allergy and Infectious Disease/Food Allergy Anaphylaxis Network (NIAID/FAAN) and the World Allergy Organization (WAO). BC convened an expert working group to revise the case definition based on their usual process of literature review and expert consensus. This manuscript presents the outcome of this process and proposes a revised case definition for anaphylaxis. Major and minor criteria have been re-evaluated with an emphasis on the reporting of observable clinical signs, rather than subjective symptoms, and a clearer approach to the ascertainment of levels of certainty is provided. The BC case definition has also been aligned with other contemporary and international case definitions for anaphylaxis.

Thrombosis and thromboembolism: Brighton collaboration case definition and guidelines for data collection, analysis, and presentation of immunization safety data.

This is a Brighton Collaboration case definition of thrombosis and thromboembolism to be used in the evaluation of adverse events following immunization, and for epidemiologic studies for the assessment of background incidence or hypothesis testing. The case definition was developed by a group of experts convened by the Coalition for Epidemic Preparedness Innovations (CEPI) in the context of active development of SARS-CoV-2 vaccines. The case definition format of the Brighton Collaboration was followed to develop a consensus definition and defined levels of certainty, after an exhaustive review of the literature and expert consultation. The document underwent peer review by the Brighton Collaboration Network and by selected expert reviewers prior to submission.

Case report: probable transmission of vaccine strain of yellow fever virus to an infant via breast milk.

The 17D yellow fever vaccine is a live-virus vaccine that has been in use since the 1940s. The incidence of encephalitis after yellow fever vaccination among young infants is much higher than among children older than nine months of age. Until recently, avoidance of vaccination by breastfeeding women who have received yellow fever vaccine had been based on theoretical grounds only. We report the probable transmission of vaccine strain of yellow fever virus from a mother to her infant through breastfeeding.

The responses of Aboriginal Canadians to adjuvanted pandemic (H1N1) 2009 influenza vaccine.

BACKGROUND: Because many Aboriginal Canadians had severe cases of pandemic (H1N1) 2009 influenza, they were given priority access to vaccine. However, it was not known if the single recommended dose would adequately protect people at high risk, prompting our study to assess responses to the vaccine among Aboriginal Canadians. METHODS: We enrolled First Nations and Métis adults aged 20-59 years in our prospective cohort study. Participants were given one 0.5-mL dose of ASO3-adjuvanted pandemic (H1N1) 2009 vaccine (Arepanrix, GlaxoSmithKline Canada). Blood samples were taken at baseline and 21-28 days after vaccination. Paired sera were tested for hemagglutination-inhibiting antibodies at a reference laboratory. To assess vaccine safety, we monitored the injection site symptoms of each participant for seven days. We also monitored patients for general symptoms within 7 days of vaccination and any use of the health care system for 21-28 days after vaccination. RESULTS: We enrolled 138 participants in the study (95 First Nations, 43 Métis), 137 of whom provided all safety data and 136 of whom provided both blood samples. First Nations and Métis participants had similar characteristics, including high rates of chronic health conditions (74.4%-76.8%). Pre-existing antibody to the virus was detected in 34.3% of the participants, all of whom boosted strongly with vaccination (seroprotection rate [titre ≥ 40] 100%, geometric mean titre 531-667). Participants with no pre-existing antibody also responded well. Fifty-eight of 59 (98.3%) First Nations participants showed seroprotection and a geometric mean titre of 353.6; all 30 Métis participants with no pre-existing antibody showed seroprotection and a geometric mean titre of 376.2. Pain at the injection site and general symptoms frequently occurred but were short-lived and generally not severe, although three participants (2.2%) sought medical attention for general symptoms. INTERPRETATION: First Nations and Métis adults responded robustly to ASO3-adjuvanted pandemic (H1N1) 2009 vaccine. Virtually all participants showed protective titres, including those with chronic health conditions.

The critical role of background rates of possible adverse events in the assessment of COVID-19 vaccine safety.

Beginning in December of 2019, a novel coronavirus, SARS-CoV-2, emerged in China and is now a global pandemic with extensive morbidity and mortality. With the emergence of this threat, an unprecedented effort to develop vaccines against this virus began. As vaccines are now being introduced globally, we face the prospect of millions of people being vaccinated with multiple types of vaccines many of which use new vaccine platforms. Since medical events happen without vaccines, it will be important to know at what rate events occur in the background so that when adverse events are identified one has a frame of reference with which to compare the rates of these events so as to make an initial assessment as to whether there is a potential safety concern or not. Background rates vary over time, by geography, by sex, socioeconomic status and by age group. Here we describe two key steps for post-introduction safety evaluation of COVID-19 vaccines: Defining a dynamic list of Adverse Events of Special Interest (AESI) and establishing background rates for these AESI. We use multiple examples to illustrate use of rates and caveats for their use. In addition we discuss tools available from the Brighton Collaboration that facilitate case evaluation and understanding of AESI.

Vaccine-associated enhanced disease: Case definition and guidelines for data collection, analysis, and presentation of immunization safety data.

This is a Brighton Collaboration Case Definition of the term "Vaccine Associated Enhanced Disease" to be utilized in the evaluation of adverse events following immunization. The Case Definition was developed by a group of experts convened by the Coalition for Epidemic Preparedness Innovations (CEPI) in the context of active development of vaccines for SARS-CoV-2 vaccines and other emerging pathogens. The case definition format of the Brighton Collaboration was followed to develop a consensus definition and defined levels of certainty, after an exhaustive review of the literature and expert consultation. The document underwent peer review by the Brighton Collaboration Network and by selected Expert Reviewers prior to submission.

Importance of background rates of disease in assessment of vaccine safety during mass immunisation with pandemic H1N1 influenza vaccines.

Because of the advent of a new influenza A H1N1 strain, many countries have begun mass immunisation programmes. Awareness of the background rates of possible adverse events will be a crucial part of assessment of possible vaccine safety concerns and will help to separate legitimate safety concerns from events that are temporally associated with but not caused by vaccination. We identified background rates of selected medical events for several countries. Rates of disease events varied by age, sex, method of ascertainment, and geography. Highly visible health conditions, such as Guillain-Barré syndrome, spontaneous abortion, or even death, will occur in coincident temporal association with novel influenza vaccination. On the basis of the reviewed data, if a cohort of 10 million individuals was vaccinated in the UK, 21.5 cases of Guillain-Barré syndrome and 5.75 cases of sudden death would be expected to occur within 6 weeks of vaccination as coincident background cases. In female vaccinees in the USA, 86.3 cases of optic neuritis per 10 million population would be expected within 6 weeks of vaccination. 397 per 1 million vaccinated pregnant women would be predicted to have a spontaneous abortion within 1 day of vaccination.

Ongoing control of Haemophilus influenzae type B infections in Canadian children, 2004-2007.

The uniform use in Canada of a single Haemophilus influenzae type b conjugate vaccine in combination with diphtheria, tetanus, acellular pertussis, and inactivated poliovirus vaccines (DTaP.IPV/Hib) facilitates ongoing assessment of vaccine effectiveness, including any effects of recently added concurrent vaccinations and increasing time since vaccination. Surveillance at 12 pediatric centers in 2004-2007 indicates that vaccine failures remain rare and case totals approach an irreducible minimum, with no age shift.

The epidemiology of children hospitalized with herpes zoster in Canada: Immunization Monitoring Program, Active (IMPACT), 1991-2005.

BACKGROUND: Varicella zoster virus causes varicella (chickenpox) and can reactivate to cause herpes zoster (HZ). In Canada, live attenuated varicella vaccine was recommended for routine use among healthy susceptible children age 1 year and older, in 1999. Varicella vaccine has had a profound impact on the incidence of varicella; however the impact on HZ remains uncertain. METHODS: Surveillance for HZ admissions was conducted by the Immunization Monitoring Program, Active (IMPACT) surveillance network comprising 12 centers representing over 90% of pediatric tertiary care beds in Canada. Active surveillance for HZ was undertaken in 1991-1996 and reintroduced in 1999. A clinical diagnosis was accepted, with or without laboratory confirmation. For each case, a detailed case report form was completed. RESULTS: In total, 648 children were admitted with HZ; 342 (52.8%) were boys and the mean age was 9.9 +/- 4.4 years. Five hundred seventy-seven (89.0%) were immunocompromised and 71 immunocompetent (10.8%). Five hundred seventy-one (88.1%) had a history of varicella zoster virus infection. Varicella vaccination was documented in 4 children before admission. Most (85.5%) presented with localized disease. Immunocompetent children were more likely than immunocompromised children to be hospitalized with ophthalmic disease (odds ratio 5.1, P < 0.001) or with at least 1 complication (odds ratio 3.0, P < 0.001). Only 1 death was attributable to HZ. CONCLUSIONS: Immunocompromised children represented the overwhelming majority of IMPACT hospitalized cases. Complications directly resulting from HZ were common in immunocompetent children. As varicella vaccine use becomes more widespread, the IMPACT network will continue to play an important role in monitoring the changing epidemiology of HZ in children.

Invasive infections caused by haemophilus influenzae serotypes in twelve Canadian IMPACT centers, 1996-2001.

BACKGROUND: Haemophilus influenzae type b (Hib) immunization has changed the epidemiology of pediatric bacterial invasive disease. We describe the epidemiology of H. influenzae invasive infections in 12 Canadian pediatric tertiary care [Immunization Monitoring Program, ACTive (IMPACT)] centers during the era of universal immunization against this pathogen. METHODS: Children with positive cultures for H. influenzae serotypes a to f (Hia to Hif) and nontypable H. influenzae from sterile sites were identified from the laboratory records at 12 IMPACT centers from January 1, 1996 to December 31, 2001. Hospital records were retrospectively reviewed for demographic and clinical information. RESULTS: Of 166 H. influenzae cases, 58 (35%) were caused by Hib, 89 (54%) by non-b serotypes, and 19 (11%) were not serotyped. The non-b serotypes included: 25 Hia (28%), 4 Hid (4%), 2 Hie (2%), 11 Hif (12%), and 47 were nontypable isolates (53%). For patients with Hib and Hia infection, meningitis was the most common presentation, accounting for 40% and 52% respectively, whereas the most common presentation for nontypable serotypes was pneumonia, seen in 43% of cases. Epiglottitis was associated mainly with Hib. Aboriginal ethnicity was an important risk factor for Hia cases, accounting for 76% of patients with infections caused by this serotype. Mean duration of hospitalization, need for admission to a pediatric intensive care unit, and case fatality rates were similar for the cases because of Hib, Hia, Hif, and nontypable serotypes. CONCLUSIONS: In 1996-2001, two-thirds of H. influenzae invasive disease in the 12 IMPACT centers was caused by non-b serotypes, which were associated with significant morbidity and mortality.

A UMLS-based spell checker for natural language processing in vaccine safety.

BACKGROUND: The Institute of Medicine has identified patient safety as a key goal for health care in the United States. Detecting vaccine adverse events is an important public health activity that contributes to patient safety. Reports about adverse events following immunization (AEFI) from surveillance systems contain free-text components that can be analyzed using natural language processing. To extract Unified Medical Language System (UMLS) concepts from free text and classify AEFI reports based on concepts they contain, we first needed to clean the text by expanding abbreviations and shortcuts and correcting spelling errors. Our objective in this paper was to create a UMLS-based spelling error correction tool as a first step in the natural language processing (NLP) pipeline for AEFI reports. METHODS: We developed spell checking algorithms using open source tools. We used de-identified AEFI surveillance reports to create free-text data sets for analysis. After expansion of abbreviated clinical terms and shortcuts, we performed spelling correction in four steps: (1) error detection, (2) word list generation, (3) word list disambiguation and (4) error correction. We then measured the performance of the resulting spell checker by comparing it to manual correction. RESULTS: We used 12,056 words to train the spell checker and tested its performance on 8,131 words. During testing, sensitivity, specificity, and positive predictive value (PPV) for the spell checker were 74% (95% CI: 74-75), 100% (95% CI: 100-100), and 47% (95% CI: 46%-48%), respectively. CONCLUSION: We created a prototype spell checker that can be used to process AEFI reports. We used the UMLS Specialist Lexicon as the primary source of dictionary terms and the WordNet lexicon as a secondary source. We used the UMLS as a domain-specific source of dictionary terms to compare potentially misspelled words in the corpus. The prototype sensitivity was comparable to currently available tools, but the specificity was much superior. The slow processing speed may be improved by trimming it down to the most useful component algorithms. Other investigators may find the methods we developed useful for cleaning text using lexicons specific to their area of interest.

Paediatric Investigators Collaborative Network on Infections in Canada (PICNIC) study of aseptic meningitis.

BACKGROUND: The seasonality, clinical and radiographic features and outcome of aseptic meningitis have been described for regional outbreaks but data from a wider geographic area is necessary to delineate the epidemiology of this condition. METHODS: A retrospective chart review was completed of children presenting with aseptic meningitis to eight Canadian pediatric hospitals over a two-year period. RESULTS: There were 233 cases of proven enteroviral (EV) meningitis, 495 cases of clinical aseptic meningitis and 74 cases of possible aseptic meningitis with most cases occurring July to October. Headache, vomiting, meningismus and photophobia were more common in children > or = 5 years of age, while rash, diarrhea and cough were more common in children < 5 years of age. Pleocytosis was absent in 22.3% of children < 30 days of age with proven EV meningitis. Enterovirus was isolated in cerebrospinal fluid (CSF) from 154 of 389 patients (39.6%) who had viral culture performed, and a nucleic acid amplification test for enterovirus was positive in CSF from 81 of 149 patients (54.3%). Imaging of the head by computerized tomography or magnetic resonance imaging was completed in 96 cases (19.7%) and 24 had abnormal findings that were possibly related to meningitis while none had changes that were definitely related to meningitis. There was minimal morbidity and there were no deaths. CONCLUSION: The clinical presentation of aseptic meningitis varies with the age of the child. Absence of CSF pleocytosis is common in infants < 30 days of age. Enterovirus is the predominant isolate, but no etiologic agent is identified in the majority of cases of aseptic meningitis in Canadian children.

Seven fatal varicella infections in children were potentially avoidable: A report from IMPACT centres from 2000 to 2005.

A varicella vaccine for children has been readily available in Canada since 2000, but some parents and physicians doubt the need for it. The Immunization Monitoring Program, ACTive (IMPACT) network of pediatric hospitals tabulated 1900 varicella-related hospitalizations and seven varicella-related deaths from 2000 to 2005. The present report describes these fatal cases, demonstrating the unpredictable and avoidable nature of life-threatening varicella complications. The knowledge that healthy children can die of chickenpox could influence parents to accept the recommended vaccination. Deaths from varicella should cease to occur, given the safe alternative of, and free access to, vaccination in current provincial programs.