Adverse events and vaccination-the lack of power and predictability of infrequent events in pre-licensure study

Methodical advances in reproducibility research: A proof of concept qualitative comparative analysis of reproducing animal data in humans

BACKGROUND

While the term reproducibility crisis mainly reflects reproducibility of experiments between laboratories, reproducibility between species also remains problematic. We previously summarised the published reproducibility between animal and human studies; i.e. the translational success rates, which varied from 0% to 100%. Based on analyses of individual factors, we could not predict reproducibility. Several potential analyses can assess effect of combinations of predictors on an outcome. Regression analysis (RGA) is common, but not ideal to analyse multiple interactions and specific configurations (≈ combinations) of variables, which could be highly relevant to reproducibility. Qualitative comparative analysis (QCA) is based on set theory and Boolean algebra, and was successfully used in other fields. We reanalysed the data from our preceding review with QCA.

RESULTS

This QCA resulted in the following preliminary formula for successful translation: ∼Old*∼Intervention*∼Large*MultSpec*Quantitative Which means that within the analysed dataset, the combination of relative recency (∼ means not; >1999), analyses at event or study level (not at intervention level), n < 75, inclusion of more than one species and quantitative (instead of binary) analyses always resulted in successful translation (>85%). Other combinations of factors showed less consistent or negative results. An RGA on the same data did not identify any of the included variables as significant contributors.

CONCLUSIONS

While these data were not collected with the QCA in mind, they illustrate that the approach is viable and relevant for this research field. The QCA seems a highly promising approach to furthering our knowledge on between-species reproducibility.

Australasian Institute of Digital Health Summit 2022-Automated Social Media Surveillance for Detection of Vaccine Safety Signals: A Validation Study

BACKGROUND

Social media platforms have emerged as a valuable data source for public health research and surveillance. Monitoring of social media and user-generated data on the Web enables timely and inexpensive collection of information, overcoming time lag and cost of traditional health reporting systems.

OBJECTIVES

This article identifies personally experienced coronavirus disease 2019 (COVID-19) vaccine reactions expressed on Twitter and validate the findings against an established vaccine reactions reporting system.

METHODS

We collected around 3 million tweets from 1.4 million users between February 1, 2021, to January 31, 2022, using COVID-19 vaccines and vaccine reactions keyword lists. We performed topic modeling on a sample of the data and applied a modified F1 scoring technique to identify a topic that best differentiated vaccine-related personal health mentions. We then manually annotated 4,000 of the records from this topic, which were used to train a transformer-based classifier to identify likely personally experienced vaccine reactions. Applying the trained classifier to the entire data set allowed us to select records we could use to quantify potential vaccine side effects. Adverse events following immunization (AEFI) referred to in these records were compared with those reported to the state of Victoria's spontaneous vaccine safety surveillance system, SAEFVIC (Surveillance of Adverse Events Following Vaccination In the Community).

RESULTS

The most frequently mentioned potential vaccine reactions generally aligned with SAEFVIC data. Notable exceptions were increased Twitter reporting of bleeding-related AEFI and allergic reactions, and more frequent SAEFVIC reporting of cardiac AEFI.

CONCLUSION

Social media conversations are a potentially valuable supplementary data source for detecting vaccine adverse event mentions. Monitoring of online observations about new vaccine-related personal health experiences has the capacity to provide early warnings about emerging vaccine safety issues.

Is vaccine hesitancy justified? Benchmarking post-market vaccine risks with five commonly used medicinal products in Canada

Objective

Although vaccines are one of the most cost-effective, low-risk healthcare approaches that save thousands of lives every year, paradoxical fear about vaccine safety is a major roadblock for achieving widespread vaccination coverage. The objective of this study is to change public perception of vaccine safety by presenting real-world incidence of adverse events following immunization (AEFIs).

Methods

In this study, we used Canadian post-market adverse events data to estimate the real-world risk of AEFI and benchmarked them against five commonly used drug types—ACE inhibitors, beta2 adrenergic receptors, penicillins, proton pump inhibitors, and HMG-CoA reductase inhibitors.

Results

Our analysis shows that post-market AEFIs are rare, and vaccination generally carries a significantly lower risk compared to some commonly used medicinal product types.

Conclusion

Despite some limitations with using post-trial adverse events data, we believe that the evidence presented in this study, especially the comparative risk analysis between vaccines and medicinal products, when communicated through proper channels, can help vaccine-hesitant individuals overcome their perceived safety concerns with regard to vaccines.

Vaccine adverse event mentions in social media: Mining the language of Twitter conversations (Preprint)

Background

Traditional monitoring for adverse events following immunization (AEFI) relies on various established reporting systems, where there is inevitable lag between an AEFI occurring and its potential reporting and subsequent processing of reports. AEFI safety signal detection strives to detect AEFI as early as possible, ideally close to real time. Monitoring social media data holds promise as a resource for this.

Objective

The primary aim of this study is to investigate the utility of monitoring social media for gaining early insights into vaccine safety issues, by extracting vaccine adverse event mentions (VAEMs) from Twitter, using natural language processing techniques. The secondary aims are to document the natural language processing techniques used and identify the most effective of them for identifying tweets that contain VAEM, with a view to define an approach that might be applicable to other similar social media surveillance tasks.

Methods

A VAEM-Mine method was developed that combines topic modeling with classification techniques to extract maximal VAEM posts from a vaccine-related Twitter stream, with high degree of confidence. The approach does not require a targeted search for specific vaccine reaction–indicative words, but instead, identifies VAEM posts according to their language structure.

Results

The VAEM-Mine method isolated 8992 VAEMs from 811,010 vaccine-related Twitter posts and achieved an F₁ score of 0.91 in the classification phase.

Conclusions

Social media can assist with the detection of vaccine safety signals as a valuable complementary source for monitoring mentions of vaccine adverse events. A social media–based VAEM data stream can be assessed for changes to detect possible emerging vaccine safety signals, helping to address the well-recognized limitations of passive reporting systems, including lack of timeliness and underreporting.

Vaccinomics and Adversomics in the Era of Precision Medicine: A Review Based on HBV, MMR, HPV, and COVID-19 Vaccines

Precision medicine approaches based on pharmacogenomics are now being successfully implemented to enable physicians to predict more efficient treatments and prevention strategies for a given disease based on the genetic background of the patient. This approach has already been proposed for vaccines, but research is lagging behind the needs of society, and precision medicine is far from being implemented here. While vaccinomics concerns the effectiveness of vaccines, adversomics concerns their side effects. This area has great potential to address public concerns about vaccine safety and to promote increased public confidence, higher vaccination rates, and fewer serious adverse events in genetically predisposed individuals. The aim here is to explore the contemporary scientific literature related to the vaccinomic and adversomic aspects of the three most-controversial vaccines: those against hepatitis B, against measles, mumps, and rubella, and against human Papilloma virus. We provide detailed information on the genes that encode human leukocyte antigen, cytokines and their receptors, and transcription factors and regulators associated with the efficacy and safety of the Hepatitis B and Measles, Mumps and Rubella virus vaccines. We also investigate the future prospects of vaccinomics and adversomics of a COVID-19 vaccine, which might represent the fastest development of a vaccine ever.

Safety of Human Papillomavirus Vaccines: An Updated Review

Human papillomavirus (HPV) vaccines are now included in immunisation programmes in 71 countries. Unfortunately, uptake has been impacted in some countries by reduced confidence in the safety of the HPV vaccine. In 2013, we published an extensive review demonstrating a reassuring safety profile for bivalent (2vHPV) and quadrivalent (4vHPV) vaccines. A nonavalent (9vHPV) vaccine is now available and HPV immunisation programmes have been extended to males in 11 countries. The aim of this updated narrative review was to examine the evidence on HPV vaccine safety, focusing on the 9vHPV vaccine, special populations and adverse events of special interest (AESI). The previous searches were replicated to identify studies to August 2016, including additional search terms for AESI. We identified 109 studies, including 15 population-based studies in over 2.5 million vaccinated individuals across six countries. All vaccines demonstrated an acceptable safety profile; injection-site reactions were slightly more common for 9vHPV vaccine than for 4vHPV vaccine. There was no consistent evidence of an increased risk of any AESI, including demyelinating syndromes or neurological conditions such as complex regional pain or postural orthostatic tachycardia syndromes. The risk-benefit profile for HPV vaccines remains highly favourable.

International collaboration to assess the risk of Guillain Barré Syndrome following Influenza A (H1N1) 2009 monovalent vaccines

BACKGROUND

The global spread of the 2009 novel pandemic influenza A (H1N1) virus led to the accelerated production and distribution of monovalent 2009 Influenza A (H1N1) vaccines (pH1N1). This pandemic provided the opportunity to evaluate the risk of Guillain-Barré syndrome (GBS), which has been an influenza vaccine safety concern since the swine flu pandemic of 1976, using a common protocol among high and middle-income countries. The primary objective of this project was to demonstrate the feasibility and utility of global collaboration in the assessment of vaccine safety, including countries both with and without an established infrastructure for vaccine active safety surveillance. A second objective, included a priori, was to assess the risk of GBS following pH1N1 vaccination.

METHODS

The primary analysis used the self-controlled case series (SCCS) design to estimate the relative incidence (RI) of GBS in the 42 days following vaccination with pH1N1 vaccine in a pooled analysis across databases and in analysis using a meta-analytic approach.

RESULTS

We found a relative incidence of GBS of 2.42 (95% CI 1.58-3.72) in the 42 days following exposure to pH1N1 vaccine in analysis of pooled data and 2.09 (95% CI 1.28-3.42) using the meta-analytic approach.

CONCLUSIONS

This study demonstrates that international collaboration to evaluate serious outcomes using a common protocol is feasible. The significance and consistency of our findings support a conclusion of an association between 2009 H1N1 vaccination and GBS. Given the rarity of the event the relative incidence found does not provide evidence in contradiction to international recommendations for the continued use of influenza vaccines.

Healthcare providers' knowledge, experience and challenges of reporting adverse events following immunisation: a qualitative study

Background

Healthcare provider spontaneous reporting of suspected adverse events following immunisation (AEFI) is central to monitoring post-licensure vaccine safety, but little is known about how healthcare professionals recognise and report to surveillance systems. The aim of this study was explore the knowledge, experience and attitudes of medical and nursing professionals towards detecting and reporting AEFI.

Methods

We conducted a qualitative study, using semi-structured, face to face interviews with 13 Paediatric Emergency Department consultants from a tertiary paediatric hospital, 10 General Practitioners, 2 local council immunisation and 4 General Practice nurses, recruited using purposive sampling in Adelaide, South Australia, between December 2010 and September 2011. We identified emergent themes related to previous experience of an AEFI in practice, awareness and experience of AEFI reporting, factors that would facilitate or impede reporting and previous training in vaccine safety. Thematic analysis was used to analyse the data.

Results

AEFI reporting was infrequent across all groups, despite most participants having reviewed an AEFI. We found confusion about how to report an AEFI and variability, according to the provider group, as to the type of events that would constitute a reportable AEFI. Participants’ interpretation of a “serious” or “unexpected” AEFI varied across the three groups. Common barriers to reporting included time constraints and unsatisfactory reporting processes. Nurses were more likely to have received formal training in vaccine safety and reporting than medical practitioners.

Conclusions

This study provides an overview of experience and beliefs of three healthcare professional groups in relation to identifying and reporting AEFI. The qualitative assessment reveals differences in experience and awareness of AEFI reporting across the three professional groups. Most participants appreciated the importance of their role in AEFI surveillance and monitoring the ongoing safety of vaccines. Future initiatives to improve education, such as increased training to health care providers, particularly, medical professionals, are required and should be included in both undergraduate curricula and ongoing, professional development.

Vaccinomics, adversomics, and the immune response network theory: individualized vaccinology in the 21st century

Vaccines, like drugs and medical procedures, are increasingly amenable to individualization or personalization, often based on novel data resulting from high throughput "omics" technologies. As a result of these technologies, 21st century vaccinology will increasingly see the abandonment of a "one size fits all" approach to vaccine dosing and delivery, as well as the abandonment of the empiric "isolate-inactivate-inject" paradigm for vaccine development. In this review, we discuss the immune response network theory and its application to the new field of vaccinomics and adversomics, and illustrate how vaccinomics can lead to new vaccine candidates, new understandings of how vaccines stimulate immune responses, new biomarkers for vaccine response, and facilitate the understanding of what genetic and other factors might be responsible for rare side effects due to vaccines. Perhaps most exciting will be the ability, at a systems biology level, to integrate increasingly complex high throughput data into descriptive and predictive equations for immune responses to vaccines. Herein, we discuss the above with a view toward the future of vaccinology.

Physicians' confidence in vaccine safety studies

OBJECTIVES

To ascertain, through two separate surveys among nationally representative networks of pediatricians (Peds) and family physicians (FM): 1) physicians' reported level of confidence in pre- and post-licensure vaccine safety studies; and 2) changes in reported level of confidence from 2007 to 2010/11.

METHODS

Two surveys were conducted in August to October 2007 and in November 2010 to January 2011. The survey response rates were 81% (FM, 79%, Peds, 84%, p=0.07) for the 2007 survey (691/848) and 66% (FM, 61%, Peds, 70%, p=0.003) for the 2010/11 survey (532/811).

RESULTS

One in three family physicians compared to one in ten pediatricians in both surveys reported little or no confidence in pre-licensure vaccine safety studies (p<0.001). Compared to pre-licensure studies, higher percentages of both specialties reported a great deal of confidence in post-licensure vaccine safety studies in both years, and more physicians from both specialties reported a great deal of confidence in 2010/11 than in 2007.

CONCLUSION

While most family physicians and pediatricians report confidence in post-licensure vaccine safety studies, one third of family physicians report little or no confidence in pre-licensure studies. More research is needed to better understand the reasons behind some physicians' lack of confidence in vaccine safety studies.

A population based cohort study to assess the safety of pandemic influenza vaccine Focetria in Emilia-Romagna region, Italy - part two

INTRODUCTION

A two phases post authorization safety and effectiveness study of individuals vaccinated with the MF59-adjuvanted A/H1N1 influenza vaccine, Focetria (Novartis Vaccines & Diagnostics, Siena, Italy), was conducted in Emilia-Romagna region, Italy during the 2009 A/H1N1 influenza pandemic. The second phase study aim was to detect short- and long-term adverse events of special interest (AESIs) following vaccination, and to measure vaccine effectiveness in term of hospital admissions.

STUDY DESIGN AND METHOD

A population-based cohort study using record linkage of automated healthcare databases is described. Focetria was administered to 127,522 subjects between October 2009 and February 2010. Vaccinated subjects were generally less healthy than unvaccinated ones. Propensity to be vaccinated was calculated for each subject, and vaccinated and unvaccinated subjects were matched accordingly (103,642 subjects in each group). AESIs were validated against clinical records.

RESULTS

In the overall (pre-matching) cohort, a total of 504 short-term incident AESIs (28 in 127,522 vaccinated and 476 in 3,967,917 unvaccinated subjects) were registered (unadjusted OR: 1.8; 95% CI: 1.2, 2.7). No fatalities were recorded. In the matched cohort, a total of 26 short-term incident AESIs (11 in the vaccinated and 15 in the unvaccinated group) were registered, with no differences between groups (OR: 0.7; 95% CI: 0.3, 1.6). Most frequent short-term incident AESIs were convulsions (4 out of 11), and demyelinating diseases (3 out of 11). In the long-term a total of 121 incident AESIs (60 in the vaccinated and 61 in the unvaccinated group) were registered, with no differences between groups (OR: 1.0; 95% CI: 0.7, 1.4). Most common long-term incident AESIs were demyelinating diseases (21 out of 60), and vasculitis (13 out of 60). Vaccine effectiveness was not assessed as the majority of subjects were vaccinated at the end of the pandemic peak and few cases (<0.1%) had laboratory confirmation.

CONCLUSIONS

This population-based cohort study using automated databases suggests that Focetria is not associated with an increase in AESIs.

Size of clinical trials and Introductory prices of prophylactic vaccine series

Costs of completing the recommended immunization schedule have increased over the last decade. Access to prophylactic vaccines may become limited due to financing obstacles within current delivery systems. Vaccine prices reflect research and development expenses incurred by vaccine manufacturers, including costs associated with evaluating candidate vaccines in human subjects. If the number of subjects in clinical trials is increasing over time and associated with vaccine price, this may help explain increases in prices of vaccine series. We examined whether: (A) the initial public- and private-sector prices for recommended prophylactic vaccine series licensed and recommended in the US increased from 2000–2011, (B) the number of human subjects per licensed vaccine increased during the time period, and (C) the number of human subjects was associated with the initial public–and private–sector prices of the vaccine series. In regression analyses of 13 vaccines, approval year was not significantly associated with the number of human subjects, initial public-sector prices, or initial private-sector prices. While the number of phase II subjects was not significantly associated with prices, the numbers of phase III and combined late phase (phases II + III) subjects were significantly associated with initial public- and private-sector series prices (p < 0.05). The association between number of subjects and initial prices demonstrated diminishing marginal increases in price with increasing numbers of subjects. These findings may help guide the number of subjects required by the FDA in clinical trials, in order to reduce expenses for manufacturers and thereby help mitigate increases in initial vaccine series prices.

Advances in the vaccination of the elderly against influenza: role of a high-dose vaccine

On 23 December 2009, the US FDA approved Fluzone&#x00AE; High Dose, a high-dose formulation of the trivalent inactivated influenza vaccine, for prevention of influenza in people 65 years of age and older. As it was approved via an accelerated process designed to allow expeditious availability of safe and effective products with promise to treat or prevent serious or life-threatening diseases, the manufacturer is required to conduct further studies to demonstrate effectiveness. Although these studies are underway, a recently completed randomized, controlled trial demonstrated that this vaccine, containing four-times more hemagglutinin than standard-dose inactivated influenza vaccines, can produce an enhanced immunologic response in subjects of 65 years of age and older, while maintaining a favorable safety profile. This article introduces the vaccine, presents currently available safety and immunogenicity data, discusses current recommendations for use, and proposes what we can expect in the coming years.

What should an ideal vaccine postlicensure safety system be?

In 2007 the National Vaccine Program, along with the Centers for Disease Control and Prevention, the Food and Drug Administration, the National Institutes of Health, and the Health Resources and Services Administration, sponsored a public conference titled "Vaccine Safety Evaluation: Post Marketing Surveillance." The objective was to discuss enhanced approaches to postlicensure evaluation of vaccine safety, including active and passive surveillance systems and special studies. The conference participants reviewed the evolution of the assessment of vaccine safety, detailed current national approaches to postmarketing safety, and offered new approaches to evaluating vaccine safety. A number of the participants recommended that information systems be expanded to include reliable information on vaccination and health outcomes in large populations. We summarize the major meeting presentations and discussions.

Why is evidence-based medicine so harsh on vaccines? An exploration of the method and its natural biases

Vaccines have been hailed as one of the greatest success stories of public health in the 20th century. The 20th century also produced a call for evidence-based medicine (EBM) with applications inclusive of preventive health. Since then, several major EBM analyses have called into question vaccine practices well-accepted by physicians, public health officials, and even the lay public. For example, while counter to existing studies and policies, EBM analyses have concluded that data are lacking to support influenza vaccination of healthcare workers to prevent flu complications among the elderly. In this review, we examine the criticisms and consider the shortcomings in the field of vaccinology as well as in the methodology of evidence-based medicine.

Autoimmunity induced by adjuvant hydrocarbon oil components of vaccine

Adjuvant oils such as Bayol F (Incomplete Freund's adjuvant: IFA) and squalene (MF59) have been used in human and veterinary vaccines despite poor understanding of their mechanisms of action. Several reports suggest an association of vaccination and various autoimmune diseases, however, few were confirmed epidemiologically and the risk of vaccination for autoimmune diseases has been considered minimal. Microbial components, not the adjuvant components, are considered to be of primary importance for adverse effects of vaccines. We have reported that a single intraperitoneal injection of the adjuvant oils pristane, IFA or squalene induces lupus-related autoantibodies to nRNP/Sm and -Su in non-autoimmune BALB/c mice. Induction of these autoantibodies appeared to be associated with the hydrocarbon's ability to induce IL-12, IL-6, and TNF-alpha, suggesting a relationship with hydrocarbon's adjuvanticity. Whether this is relevant in human vaccination is a difficult issue due to the complex effects of vaccines and the fact that immunotoxicological effects vary depending on species, route, dose, and duration of administration. Nevertheless, the potential of adjuvant hydrocarbon oils to induce autoimmunity has implications in the use of oil adjuvants in human and veterinary vaccines as well as basic research.

Intestinal imaging of children with acute rotavirus gastroenteritis

OBJECTIVE

To examine the morphology and motility of the distal small bowel of infants with rotavirus gastroenteritis using non-invasive/non-ionizing imaging technology.

METHODS

Prospective, non-randomized observational study of five infants with symptomatic rotavirus infection. Infants were imaged by real-time magnetic resonance imaging (MRI) and ultrasound within 5 days of onset of gastroenteritis symptoms. Imaging studies were repeated in the convalescent period 5 to 9 weeks later.

RESULTS

Three of five infants had a significant increase in the ileal wall thickness visualized by ultrasound during acute rotavirus infection compared with convalescence. The number and size of mesenteric lymph nodes visualized by ultrasound appeared similar in the acute and convalescent phases, as did peristaltic activity assessed by MRI.

CONCLUSION

Abdominal ultrasound can detect changes in ileal wall thickness in infants with rotavirus infection. These changes may reflect ileal inflammation elicited by viral infection. Such studies may prove useful in evaluating morphologic response to attenuated rotavirus vaccines.

Vaccine safety

Rates of reported adverse events are remarkably low. VAERS identifies an adverse event rate approximating 11.4 reports per 100,000 vaccine doses. Approximately 15% of these reports represent SAEs, but less than 2% involve death; in most cases, reviews have shown no causal relation between the events and the vaccine. Across the spectrum of vaccines in use (including those directed against influenza and hepatitis B virus), many claims of adverse events regarding vaccines represent typical reactions to vaccinations. These reactions can be thought of as foreign-body reactions and predominate among the inactivated vaccines. In controlled studies, the adverse event rates that occur with vaccination resemble those that occur with placebo injections. Typical reactions associated with live viral and bacterial vaccines, such as MMR and varicella vaccines, may resemble attenuated forms of the disease for which the vaccine is directed. Other claims against vaccines represent chance-coincidence or misunderstood data; further studies of claims have vindicated the overall safety of the vaccines in most cases. Two documented safety concerns with vaccines, however, have demonstrated that vaccines (like other biologics and pharmacologic) can result in harm (eg, rotavirus and OPV vaccines). The denouement with these vaccines indicates the broad postmarketing data collection and evaluation that extends efforts made with prelicensure study to balance the benefits from vaccination with the risk for harm. Overall, measures including prelicensure study and postlicensure surveillance, such as VAERS, the Vaccine Safety Datalink Project, and the Clinical Immunization Safety Assessment Centers, have resulted in an exceptional safety profile for the vaccines in use.

Rotavirus vaccine for preventing diarrhoea

BACKGROUND

Rotaviruses cause viral gastroenteritis and result in more deaths from diarrhoea in children under 5 years of age than any other single agent, particularly in low- and middle-income countries.

OBJECTIVES

To assess rotavirus vaccines in relation to preventing rotavirus diarrhoea, death, and adverse events.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group's trial register (October 2003), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 3, 2003), MEDLINE (1966 to October 2003), EMBASE (January 1980 to October 2003), LILACS (1982 to October 2003), Biological Abstracts (January 1982 to October 2003), reference lists of articles, and contacted researchers and rotavirus vaccine manufacturers.

SELECTION CRITERIA

Randomized controlled trials comparing rotavirus vaccines to placebo, no intervention, or other rotavirus vaccines in children and adults.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed trial methodological quality, and contacted trial authors for additional information.

MAIN RESULTS

Sixty-four trials provided information on efficacy and safety of three main types of rotavirus vaccine (bovine, human, and rhesus) for 21,070 children. Different levels of efficacy were demonstrated with different vaccines varying from 22 to 89% to prevent one episode of rotavirus diarrhoea, 11 to 44% to prevent one episode of all-cause diarrhoea, and 43 to 90% to prevent one episode of severe rotavirus diarrhoea. Rhesus vaccine demonstrated a similar efficacy against one episode of rotavirus diarrhoea (37 and 44% respectively), and one episode of all-cause diarrhoea (around 15%) for trials performed in high and middle-income countries. Results on mortality and safety of the vaccines were scarce and incomplete. We noticed important heterogeneity among the pooled studies and were unable to discard a biased estimation of effect.

REVIEWER'S CONCLUSIONS

Current evidence shows that rhesus rotavirus vaccines (particularly RRV-TV) and the human rotavirus vaccine 89-12 are efficacious in preventing diarrhoea caused by rotavirus and all-cause diarrhoea. Evidence about safety, and about mortality or prevention of severe outcomes, is scarce and inconclusive. Bovine rotavirus vaccines were also efficacious, but safety data are not available. Trials of new rotavirus vaccines will hopefully improve the evidence base. Randomized controlled trials should be performed simultaneously in high-, middle-, and low-income countries.

'Parsimonious' versus patient-centered care: quality issues in childhood immunization

As currently practiced, the standard of care strictly limiting the number of medical conditions that warrant withholding vaccination may be incompatible with the Institute of Medicine's (IOM) recommendation for patient-centered care. Furthermore, the "parsimonious" approach to accepting contraindications to vaccination is inconsistent with the IOM's recommendation to consider alternative vaccination schedules and policies aimed at redistributing the benefits and burdens of immunization. This critical perspective is examined within the framework of five rules proposed by the IOM. There is an opportunity to improve the quality of childhood immunization by adopting a patient-centered approach, identifying individuals at risk for acute and/or delayed adverse vaccine effects, and developing alternative immunization schedules for these high-risk children.

The overall safety profile of currently available vaccines directed against infectious diseases

The vaccines currently used worldwide for the prevention of infectious diseases are quite safe in comparison to most pharmaceutical and biological agents. Vaccine components may contribute to inflammatory, allergic or anaphylactic reactions. Most adverse events are transient and well-tolerated. Transient severe adverse reactions occur at rates of one in one thousand vaccinations; permanent severe adverse reactions occur on the order of one in one million. The most common of the severe adverse reactions are syncope and allergic reactions. Providers can take steps to prevent or ameliorate these reactions by pursuing both prelicensure testing (albeit limited) and postlicensure testing and monitoring. Systems that enhance the detection of safety concerns include national passive and active surveillance as well as regional vaccine registries and provider-based patient education. Since vaccines are used in universal programmes, their safety is paramount to their continued acceptance. Healthcare managers, including administrators of hospitals, clinics, practice groups, health maintenance organisations (HMOs) and managed care plans, can and should support providers in minimising adverse events associated with vaccines by supporting postvaccination observation policies, postlicensure testing and surveillance, vaccine registries and patient education systems.

Comprehensive systematic surveillance for adverse effects of anthrax vaccine adsorbed, US Armed Forces, 1998-2000

Routine vaccinations of US military personnel with Anthrax Vaccine Adsorbed began in 1998. To systematically identify clinical diagnoses reported more frequently after vaccination than before, all military personnel were retrospectively assigned to pre- or post-vaccination cohorts. Cohort assignments were based on vaccination statuses each day of the 3-year surveillance period. For each cohort, rates of hospitalizations and ambulatory visits for 843 specific diagnoses were calculated using data in a public health surveillance system. Compared to the pre-vaccination cohort, the post-vaccination cohort had statistically higher rates of hospitalizations for 17 diagnoses, of ambulatory visits for 34 diagnoses, and in both clinical settings for one diagnosis (malaria). After accounting for systematic differences in coding/reporting and residual confounding, the number and nature of clinical diagnoses more frequent after anthrax vaccination than before were consistent with expectations due to random variation. This surveillance suggests that Anthrax Vaccine Adsorbed has few, if any, clinically significant adverse effects.

Survey of human-use adjuvants

Although there are only four adjuvants used in licensed vaccines for humans, a wealth of information on novel vaccine adjuvants has become available in both animal models and clinical studies over the past decade. Many vaccine candidates require immunopotentiation to achieve a satisfactory immune response, which is driving the search for new and safer approaches. In this review, we take a brief look at what is known of the mechanisms of action, consider some of the elements of product development, then survey several of the classes of adjuvants within the context of human trials.

The Brighton Collaboration: addressing the need for standardized case definitions of adverse events following immunization (AEFI)

To further scientific progress of immunization safety, comparability of data from clinical trials and surveillance systems is essential. Comparability requires the availability of standardized case definitions for adverse events following immunization (AEFI) and guidelines for case determination, recording and data presentation.

METHOD

International collaborative working groups, consisting of professional volunteers from developed and developing countries, conduct systematic literature reviews to develop 50-100 AEFI definitions. Case definitions are finalized after a comment period by a reference group consisting of organizations concerned with immunization safety, and will be disseminated via the world-wide-web and other means for free world-wide use.

RESULTS

Literature reviews yielded substantial diversity in data collection and presentation. We have developed standardized case definitions together with guidelines for use in clinical trials and surveillance systems.

CONCLUSIONS

Diversity in safety methods leads to considerable loss of scientific information. We have built the necessary international network of currently about 300 participants from patient care, public health, scientific, pharmaceutical, regulatory and professional organizations to develop and assess standardized AEFI case definitions and guidelines. Evaluation studies, global implementation, ongoing definition development and a continuously growing network will be essential for the success of the collaboration.

Retrospective population-based assessment of medically attended injection site reactions, seizures, allergic responses and febrile episodes after acellular pertussis vaccine combined with diphtheria and tetanus toxoids

BACKGROUND

Since 1997 diphtheria-tetanus toxoids-acellular pertussis (DTaP) vaccines have been recommended for the five dose pertussis vaccination series. To assess rates of medically attended injection site reactions (ISRs), seizures, allergic responses and febrile episodes after Tripedia DTaP vaccine administered in the context of routine care, we conducted a retrospective assessment among the population of Group Health Cooperative from 1997 through 2000.

METHODS

Administrative databases were used to identify medical visits linked with diagnostic codes potentially indicative of ISRs, seizures, allergic responses and febrile episodes after DTaP vaccine. Outcomes were confirmed by medical record review.

RESULTS

During the study period 76 133 doses of DTaP were administered. Of the 26 ISRs identified, 6 followed DTaP given as the fourth dose and 18 followed DTaP given as the fifth dose, for rates of 1 per 2779 and 1 per 900 vaccinations, respectively. During the study period nearly all children receiving DTaP as the fifth dose had received whole cell pertussis vaccine for their primary series, and all of the fifth dose ISRs were among that group. Four of those reactions involved the entire upper arm. The rate of febrile seizures within 2 days of DTaP among children <2 years of age was 1 per 19 496 vaccinations.

CONCLUSIONS

The low rate of febrile seizures and other serious events confirms the safety of DTaP vaccine. The risk of medically attended ISRs was highest with DTaP given as the fifth dose, and whole arm reactions were reported, but medically attended ISRs were relatively uncommon and were self-limited.

The challenge of vaccine safety

Vaccines always will involve some risk, and risk always involves some public concern. Although the benefits of routine vaccination greatly outweigh any adverse effects, our consumer society seeks to eliminate all risk. The balance of risk and benefit appears to falter by the very success of preventing disease: in the immediate absence of the disease, the resolve to vaccinate waivers. We cannot expect the public to think in terms of the decision analyst and carefully weigh probability, risk, and benefit in a numerical fashion. In fact, the public's approach toward vaccination is varied and unscientific. Recognizing these challenges, we propose a program of continued vigilance by increasing our scientific base and methodology, improving vaccine safety communication through research and resources, maintaining a tolerance of conscientious objection as a safety valve for mandated routine vaccination in civilians, and calling for more research funding for the development of new vaccines.

The development and use of vaccine adjuvants

Interest in vaccine adjuvants is intense and growing, because many of the new subunit vaccine candidates lack sufficient immunogenicity to be clinically useful. In this review, I have emphasized modern vaccine adjuvants injected parenterally, or administered orally, intranasally, or transcutaneously with licensed or experimental vaccines in humans. Every adjuvant has a complex and often multi-factorial immunological mechanism, usually poorly understood in vivo. Many determinants of adjuvanticity exist, and each adjuvanted vaccine is unique. Adjuvant safety is critical and can enhance, retard, or stop development of an adjuvanted vaccine. The choice of an adjuvant often depends upon expensive experimental trial and error, upon cost, and upon commercial availability. Extensive regulatory and administrative support is required to conduct clinical trials of adjuvanted vaccines. Finally, comparative adjuvant trials where one antigen is formulated with different adjuvants and administered by a common protocol to animals and humans can accelerate vaccine development.