The Vaccine Safety Datalink: a model for monitoring immunization safety

Identifying birth defects in automated data sources in the Vaccine Safety Datalink

PURPOSE

The Vaccine Safety Datalink (VSD), a collaboration between the Centers for Disease Control and Prevention and several large healthcare organizations, aims to monitor safety of vaccines administered in the USA. We present definitions and prevalence estimates for major structural birth defects to be used in studies of maternal vaccine safety.

METHODS

In this observational study, we created and refined algorithms for identifying major structural birth defects from electronic healthcare data, conducted formal chart reviews for severe cardiac defects, and conducted limited chart validation for other defects. We estimated prevalence for selected defects by VSD site and birth year and compared these estimates to those in a US and European surveillance system.

RESULTS

We developed algorithms to enumerate >50 major structural birth defects from standardized administrative and healthcare data based on utilization patterns and expert opinion, applying criteria for number, timing, and setting of diagnoses. Our birth cohort included 497 894 infants across seven sites. The period prevalence for all selected major birth defects in the VSD from 2004 to 2013 was 1.7 per 100 live births. Cardiac defects were most common (65.4 per 10 000 live births), with one-fourth classified as severe, requiring emergent intervention. For most major structural birth defects, prevalence estimates were stable over time and across sites and similar to those reported in other population-based surveillance systems.

CONCLUSIONS

Our algorithms can efficiently identify many major structural birth defects in large healthcare datasets and can be used in studies evaluating the safety of vaccines administered to pregnant women. Copyright © 2017 John Wiley & Sons, Ltd.

Vaccine Case-Population: A New Method for Vaccine Safety Surveillance

INTRODUCTION

The case-population approach compares exposure among cases to that of their source population. By using aggregated data to estimate the denominator, this approach can provide a real-time estimate of an association that could be particularly valuable to explore urgent vaccine safety concerns and to generate signals during a vaccine campaign.

OBJECTIVE

Our objective was to present the vaccine case-population method, a method derived from the case-population approach and adapted for vaccine safety surveillance, and to test it using several published examples.

METHODS

For the vaccine case-population method, exposure in the population is estimated from the sum of at-risk periods using the number of vaccinated individuals, or data of vaccine sales, and the at-risk period considered for the vaccine-event pair. The vaccine case-population method was applied to data from published case-control studies retrieved from the MEDLINE database and having quantified risks associated with vaccines. Odds ratios derived from the vaccine case-population method were compared with those from published case-control studies.

RESULTS

A total of 20 vaccine-event pairs were retrieved in which the vaccine case-population method could be applied. For all identified vaccine-event pairs, when a significant association was found using the vaccine case-population method, a significant association was also found in the corresponding case-control study. Conversely, when no association was found by the vaccine case-population method, no association was found in the corresponding case-control study.

CONCLUSION

These results suggest that the vaccine case-population method can produce coherent conclusions and may be used in the future for prospective investigation of urgent vaccine safety concerns or for the prospective generation of vaccine safety signals. This method could also be used to identify selection bias from cases excluded from the case-control study.

Sepsis, parenteral vaccination and skin disinfection

ASBSTRACT Disinfection should be required for all skin penetrative procedures including parenteral administration of vaccines. This review analyses medically attended infectious events following parenteral vaccination in terms of their microbiological aetiology and pathogenesis. Like 'clean' surgical site infections, the major pathogens responsible for these events were Staphylococcal species, implicating endogenous con-tamination as a significant source of infection. As 70% isopropyl alcohol swabbing has been shown to effectively disinfect the skin, it would be medico-legally difficult to defend a case of sepsis with the omission of skin disinfection unless the very low risk of this event was adequately explained to the patient and documented prior to vaccination. There was a significant cost-benefit for skin disinfection and cellulitis. Skin disinfection in the context of parenteral vaccination represents a new paradigm of medical practice; the use of a low cost intervention to prevent an event of very low prevalence but of significant cost.

A Synthesis of Current Surveillance Planning Methods for the Sequential Monitoring of Drug and Vaccine Adverse Effects Using Electronic Health Care Data

INTRODUCTION

The large-scale assembly of electronic health care data combined with the use of sequential monitoring has made proactive postmarket drug- and vaccine-safety surveillance possible. Although sequential designs have been used extensively in randomized trials, less attention has been given to methods for applying them in observational electronic health care database settings.

EXISTING METHODS

We review current sequential-surveillance planning methods from randomized trials, and the Vaccine Safety Datalink (VSD) and Mini-Sentinel Pilot projects-two national observational electronic health care database safety monitoring programs.

FUTURE SURVEILLANCE PLANNING

Based on this examination, we suggest three steps for future surveillance planning in health care databases: (1) prespecify the sequential design and analysis plan, using available feasibility data to reduce assumptions and minimize later changes to initial plans; (2) assess existing drug or vaccine uptake, to determine if there is adequate information to proceed with surveillance, before conducting more resource-intensive planning; and (3) statistically evaluate and clearly communicate the sequential design with all those designing and interpreting the safety-surveillance results prior to implementation. Plans should also be flexible enough to accommodate dynamic and often unpredictable changes to the database information made by the health plans for administrative purposes.

CONCLUSIONS

This paper is intended to encourage dialogue about establishing a more systematic, scalable, and transparent sequential design-planning process for medical-product safety-surveillance systems utilizing observational electronic health care databases. Creating such a framework could yield improvements over existing practices, such as designs with increased power to assess serious adverse events.

Surveillance systems and methods for monitoring the post-marketing safety of influenza vaccines at the Centers for Disease Control and Prevention

INTRODUCTION

Annual influenza vaccine safety monitoring is an important component of the influenza vaccination program in the United States to ensure that vaccines are safe, which is important for maintaining public trust in the national vaccination program. This is specially the case for influenza vaccines since the antigen composition of the viruses of which the vaccine is made often changes from one season to the next, based on the circulating strain of influenza virus.

AREAS COVERED

This review describes the two surveillance systems used by the Centers for Disease Control and Prevention (CDC) to monitor the safety of influenza vaccines: 1) the Vaccine Adverse Event Reporting System (VAERS); and 2) the Vaccine Safety datalink (VSD).

EXPERT OPINION

VAERS and VSD are used routinely to monitor the safety of influenza vaccines in the United States, and over the years they have demonstrated their value in monitoring vaccine safety since their implementation in 1990. Both systems, although different, complemented each other well to study febrile seizures in young children following influenza vaccination during the 2010-2011 influenza season. Other examples of potential safety concerns after influenza vaccines are also presented and discussed.

Post licensure surveillance of influenza vaccines in the Vaccine Safety Datalink in the 2013-2014 and 2014-2015 seasons

PURPOSE

The changes in each year in influenza vaccine antigenic components as well as vaccine administration patterns may pose new risks of adverse events following immunization (AEs). To evaluate the safety of influenza vaccines annually administered to people ≥ 6 months, we conducted weekly post licensure surveillance for seven pre-specified adverse events following receipt of influenza vaccines during the 2013-2014 and 2014-2015 seasons in the Vaccine Safety Datalink (VSD).

METHODS

We used both a historically-controlled cohort design with the Poisson-based maximized sequential probability ratio test (maxSPRT) and a self-controlled risk interval (SCRI) design with the binomial-based maxSPRT. For each adverse event outcome, we defined the risk interval on the basis of biologic plausibility and prior literature. For the historical cohort design, numbers of expected adverse events were calculated from the prior seven seasons, adjusted for age and site. For the SCRI design, a comparison window was defined either before vaccination or after vaccination, depending on each specific outcome.

RESULTS

An elevated risk of febrile seizures 0-1 days following trivalent inactivated influenza vaccine (IIV3) was identified in children aged 6-23 months during the 2014-2015 season using the SCRI design. We found the relative risk (RR) of febrile seizures following concomitant administration of IIV3 and PCV13 was 5.3 with a 95% CI 1.87-14.75. Without concomitant PCV 13 administration, the estimated risk decreased and was no longer statistically significant (RR: 1.4; CI: 0.54 - 3.61).

CONCLUSION

No increased risks, other than for febrile seizures, were identified in influenza vaccine safety surveillance during 2013-2014 and 2014-2015 seasons in the VSD. Copyright © 2016 John Wiley & Sons, Ltd.

Risk of Preterm or Small-for-Gestational-Age Birth After Influenza Vaccination During Pregnancy: Caveats When Conducting Retrospective Observational Studies

Vaccines are increasingly targeted toward women of reproductive age, and vaccines to prevent influenza and pertussis are recommended during pregnancy. Prelicensure clinical trials typically have not included pregnant women, and when they are included, trials cannot detect rare events. Thus, postmarketing vaccine safety assessments are necessary. However, analysis of observational data requires detailed assessment of potential biases. Using data from 8 Vaccine Safety Datalink sites in the United States, we analyzed the association of monovalent H1N1 influenza vaccine (MIV) during pregnancy with preterm birth (<37 weeks) and small-for-gestational-age birth (birth weight < 10th percentile). The cohort included 46,549 pregnancies during 2009-2010 (40% of participants received the MIV). We found potential biases in the vaccine-birth outcome association that might occur due to variable access to vaccines, the time-dependent nature of exposure to vaccination within pregnancy (immortal time bias), and confounding from baseline differences between vaccinated and unvaccinated women. We found a strong protective effect of vaccination on preterm birth (relative risk = 0.79, 95% confidence interval: 0.74, 0.85) when we ignored potential biases and no effect when accounted for them (relative risk = 0.91; 95% confidence interval: 0.83, 1.0). In contrast, we found no important biases in the association of MIV with small-for-gestational-age birth. Investigators conducting studies to evaluate birth outcomes after maternal vaccination should use statistical approaches to minimize potential biases.

Continuous active surveillance of adverse events following immunisation using SMS technology

INTRODUCTION

On-going post-licensure surveillance of adverse events following immunisation (AEFI) is critical to detecting and responding to potentially serious adverse events in a timely manner. SmartVax is a vaccine safety monitoring tool that uses automated data extraction from existing practice management software and short message service (SMS) technology to follow-up vaccinees in real-time. We report on childhood vaccine safety surveillance using SmartVax at a medical practice in Perth, Western Australia.

METHODS

Parents of all children under age five years who were vaccinated according to the Australian National Immunisation Schedule between November 2011 and June 2015 were sent an SMS three days post administration to enquire whether the child had experienced a suspected vaccine reaction. Affirmative replies triggered a follow-up SMS requesting details of the reaction(s) via a link to a survey that could be completed using a smartphone or the web. Rates of reported AEFI including fever, headache, fatigue, rash, vomiting, diarrhoea, rigours, seizures, and local reactions were calculated by vaccination time point.

RESULTS

Overall, 239 (8.2%; 95% CI 7.2-9.2%) possible vaccine reactions were reported for 2897 vaccination visits over the 44 month time period. The proportion of children experiencing a possible AEFI, mostly local reactions, was significantly greater following administration of diphtheria-tetanus-pertussis-poliomyelitis vaccine at 4 years of age (77/441; 17.5%; 95% CI 13.9-21.0%) compared to the vaccinations given at 2-18 months (p<0.001). Across all time points, local reactions and fatigue were the most frequently reported AEFI.

CONCLUSION

Automated SMS-based reporting can facilitate sustainable, real-time, monitoring of adverse reactions and contribute to early identification of potential vaccine safety issues.

Developing an Algorithm to Identify History of Cancer Using Electronic Medical Records

Introduction/Objective:

The objective of this study was to develop an algorithm to identify Kaiser Permanente Colorado (KPCO) members with a history of cancer.

Background:

Tumor registries are used with high precision to identify incident cancer, but are not designed to capture prevalent cancer within a population. We sought to identify a cohort of adults with no history of cancer, and thus, we could not rely solely on the tumor registry.

Methods:

We included all KPCO members between the ages of 40–75 years who were continuously enrolled during 2013 (N=201,787). Data from the tumor registry, chemotherapy files, inpatient and outpatient claims were used to create an algorithm to identify members with a high likelihood of cancer. We validated the algorithm using chart review and calculated sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for occurrence of cancer.

Findings:

The final version of the algorithm achieved a sensitivity of 100 percent and specificity of 84.6 percent for identifying cancer. If we relied on the tumor registry alone, 47 percent of those with a history of cancer would have been missed.

Discussion:

Using the tumor registry alone to identify a cohort of patients with prior cancer is not sufficient. In the final version of the algorithm, the sensitivity and PPV were improved when a diagnosis code for cancer was required to accompany oncology visits or chemotherapy administration.

Conclusion:

Electronic medical record (EMR) data can be used effectively in combination with data from the tumor registry to identify health plan members with a history of cancer.

Influenza Vaccination During Pregnancy: Influenza Seasons 2002-2012, Vaccine Safety Datalink

INTRODUCTION

Pregnant women are at risk for influenza-related complications and have been recommended for vaccination by the Advisory Committee on Immunization Practices (ACIP) since 1990. Annual rates of influenza coverage of pregnant women have been consistently low. The Vaccine Safety Datalink was used to assess influenza vaccine coverage over 10 consecutive years (2002-2012); assess patterns related to changes in ACIP recommendations; identify predictors of vaccination; and compare the results with those published by national U.S. surveys.

METHODS

Retrospective cohort study of 721,898 pregnancies conducted in 2014. Coverage rates were assessed for all pregnancies and for live births only. Multivariate regression analysis identified predictors associated with vaccination.

RESULTS

Coverage increased from 8.8% to 50.9% in 2002-2012. Seasonal coverage rates increased slowly following the 2004 ACIP influenza vaccine recommendation (to remove the first trimester restriction), but spiked significantly during the 2009 H1N1 influenza pandemic. Significant predictors of vaccination during pregnancy included older age; vaccination in a previous season; high-risk conditions in addition to pregnancy; pregnancy during either the 2004-2005 or 2009-2010 seasons; entering the influenza season after the first trimester of pregnancy; and a pregnancy with longer overlap with the influenza season (p<0.001 for each).

CONCLUSIONS

Influenza vaccination coverage among pregnant women increased between the 2002-2003 and 2011-2012 seasons, although it was still below the developmental Healthy People 2020 goal of 80%. The 2004 ACIP language change positively impacted first-trimester vaccination uptake. Vaccine Safety Datalink data estimates were consistent with U.S. estimates.

Adverse events following immunization: real causality and myths

INTRODUCTION

To assure the highest safety of immunization programs, detect adverse events following immunization (AEFIs), eliminate concerns, and reduce the risk of low vaccination coverage, authorities in industrialized countries have collected years of reports of suspected AEFIs and have systematically assessed their clinical importance.

AREAS COVERED

In this paper, the methods used to assess vaccine safety and the results obtained by the analysis of reports, studies, and meta-analyses are discussed.

EXPERT OPINION

Severe AEFIs are rare, and all evaluations of safety of vaccines recommended for both children and adults have demonstrated that the advantages of vaccines are always significantly higher than the problems that they cause, and there is no need to modify recommendations. However, the definition of AEFI is dependent on the vaccines themselves, complicating the definition of an AEFI and explaining why doubts and concerns have been raised. Presently, disease epidemiology data collected in healthy people and in subjects with underlying disease, general vaccine coverage, and the vaccination status of subjects with AEFIs are managed by many independent institutions. Only strict co-operation between these institutions will lead to the successful identification of AEFIs and to a reduction of the weight of anti-vaccine arguments.

Quadrivalent HPV vaccine safety review and safety monitoring plans for nine-valent HPV vaccine in the United States

Quadrivalent human papillomavirus (4vHPV) vaccine was licensed for use in the United States in 2006 and through 2015 was the predominate HPV vaccine used. With the exception of syncope, a known preventable adverse event after any injected vaccination, both pre-licensure and post-licensure 4vHPV safety data have been reassuring with no confirmed safety signals identified. Nine-valent HPV vaccine (9vHPV) was licensed in 2014. This review includes post-licensure 4vHPV safety findings published to date that have informed the US vaccination program; these data will inform US safety monitoring and evaluation for 9vHPV.

Can Digital Tools Be Used for Improving Immunization Programs?

In order to successfully control and eliminate vaccine-preventable infectious diseases, an appropriate vaccine coverage has to be achieved and maintained. This task requires a high level of effort as it may be compromised by a number of barriers. Public health agencies have issued specific recommendations to address these barriers and therefore improve immunization programs. In the present review, we characterize issues and challenges of immunization programs for which digital tools are a potential solution. In particular, we explore previously published research on the use of digital tools in the following vaccine-related areas: immunization registries, dose tracking, and decision support systems; vaccine-preventable diseases surveillance; surveillance of adverse events following immunizations; vaccine confidence monitoring; and delivery of information on vaccines to the public. Subsequently, we analyze the limits of the use of digital tools in such contexts and envision future possibilities and challenges.

Risk of anaphylaxis after vaccination in children and adults

BACKGROUND

Anaphylaxis is a potentially life-threatening allergic reaction. The risk of anaphylaxis after vaccination has not been well described in adults or with newer vaccines in children.

OBJECTIVE

We sought to estimate the incidence of anaphylaxis after vaccines and describe the demographic and clinical characteristics of confirmed cases of anaphylaxis.

METHODS

Using health care data from the Vaccine Safety Datalink, we determined rates of anaphylaxis after vaccination in children and adults. We first identified all patients with a vaccination record from January 2009 through December 2011 and used diagnostic and procedure codes to identify potential anaphylaxis cases. Medical records of potential cases were reviewed. Confirmed cases met the Brighton Collaboration definition for anaphylaxis and had to be determined to be vaccine triggered. We calculated the incidence of anaphylaxis after all vaccines combined and for selected individual vaccines.

RESULTS

We identified 33 confirmed vaccine-triggered anaphylaxis cases that occurred after 25,173,965 vaccine doses. The rate of anaphylaxis was 1.31 (95% CI, 0.90-1.84) per million vaccine doses. The incidence did not vary significantly by age, and there was a nonsignificant female predominance. Vaccine-specific rates included 1.35 (95% CI, 0.65-2.47) per million doses for inactivated trivalent influenza vaccine (10 cases, 7,434,628 doses given alone) and 1.83 (95% CI, 0.22-6.63) per million doses for inactivated monovalent influenza vaccine (2 cases, 1,090,279 doses given alone). The onset of symptoms among cases was within 30 minutes (8 cases), 30 to less than 120 minutes (8 cases), 2 to less than 4 hours (10 cases), 4 to 8 hours (2 cases), the next day (1 case), and not documented (4 cases).

CONCLUSION

Anaphylaxis after vaccination is rare in all age groups. Despite its rarity, anaphylaxis is a potentially life-threatening medical emergency that vaccine providers need to be prepared to treat.

Vaccination and 30-Day Mortality Risk in Children, Adolescents, and Young Adults

OBJECTIVE

This study evaluates the potential association of vaccination and death in the Vaccine Safety Datalink (VSD).

METHODS

The study cohort included individuals ages 9 to 26 years with deaths between January 1, 2005, and December 31, 2011. We implemented a case-centered method to estimate a relative risk (RR) for death in days 0 to 30 after vaccination.Deaths due to external causes (accidents, homicides, and suicides) were excluded from the primary analysis. In a secondary analysis, we included all deaths regardless of cause. A team of physicians reviewed available medical records and coroner's reports to confirm cause of death and assess the causal relationship between death and vaccination.

RESULTS

Of the 1100 deaths identified during the study period, 76 (7%) occurred 0 to 30 days after vaccination. The relative risks for deaths after any vaccination and influenza vaccination were significantly lower for deaths due to nonexternal causes (RR 0.57, 95% confidence interval [CI] 0.38-0.83, and RR 0.44, 95% CI 0.24-0.80, respectively) and deaths due to all causes (RR 0.72, 95% CI 0.56-0.91, and RR 0.44, 95% CI 0.28-0.65). No other individual vaccines were significantly associated with death. Among deaths reviewed, 1 cause of death was unknown, 25 deaths were due to nonexternal causes, and 34 deaths were due to external causes. The causality assessment found no evidence of a causal association between vaccination and death.

CONCLUSIONS

Risk of death was not increased during the 30 days after vaccination, and no deaths were found to be causally associated with vaccination.

Maternal Tdap vaccination: Coverage and acute safety outcomes in the vaccine safety datalink, 2007-2013

INTRODUCTION

Since October 2012, the combined tetanus toxoid, reduced diphtheria toxoid, acellular pertussis vaccine (Tdap) has been recommended in the United States during every pregnancy.

METHODS

In this observational study from the Vaccine Safety Datalink, we describe receipt of Tdap during pregnancy among insured women with live births across seven health systems. Using a retrospective matched cohort, we evaluated risks for selected medically attended adverse events in pregnant women, occurring within 42 days of vaccination. Using a generalized estimating equation, we calculated adjusted incident rate ratios (AIRR).

RESULTS

Our vaccine coverage cohort included 438,487 live births between January 1, 2007 and November 15, 2013. Across the coverage cohort, 14% received Tdap during pregnancy. By 2013, Tdap was administered during pregnancy in 41.7% of live births, primarily in the 3rd trimester. Our vaccine safety cohort included 53,885 vaccinated and 109,253 matched unvaccinated pregnant women. There was no increased risk for a composite outcome of medically attended acute adverse events within 3 days of vaccination. Similarly, across the safety cohort, over a 42 day window, incident neurologic events, thrombotic events, and new onset proteinuria did not differ by maternal receipt of Tdap. Among women receiving Tdap at 20 weeks gestation or later, as compared to their matched controls, there was no increased risk for gestational diabetes or cardiac events while venous thromboembolic events and thrombocytopenia were diagnosed within 42 days of vaccination at slightly decreased rates.

CONCLUSION

Tdap coverage during pregnancy increased from 2007 through 2013, but was still below 50%. No acute maternal safety signals were detected in this large cohort.

The Pioneering Role of the Vaccine Safety Datalink Project (VSD) to Advance Collaborative Research and Distributed Data Networks

Introduction:

Large-scale distributed data networks consisting of diverse stakeholders including providers, patients, and payers are changing health research in terms of methods, speed and efficiency. The Vaccine Safety Datalink (VSD) set the stage for expanded involvement of health plans in collaborative research.

Expanding Surveillance Capacity and Progress Toward a Learning Health System:

From an initial collaboration of four integrated health systems with fewer than 10 million covered lives to 16 diverse health plans with nearly 100 million lives now in the FDA Sentinel, the expanded engagement of health plan researchers has been essential to increase the value and impact of these efforts. The collaborative structure of the VSD established a pathway toward research efforts that successfully engage all stakeholders in a cohesive rather than competitive manner. The scientific expertise and methodology developed through the VSD such as rapid cycle analysis (RCA) to conduct near real-time safety surveillance allowed for the development of the expanded surveillance systems that now exist.

Building on Success and Lessons Learned:

These networks have learned from and built on the knowledge base and infrastructure created by the VSD investigators. This shared technical knowledge and experience expedited the development of systems like the FDA’s Mini-Sentinel and the Patient Centered Outcomes Research Institute (PCORI)’s PCORnet

Conclusion:

This narrative reviews the evolution of the VSD, its contribution to other collaborative research networks, longer-term sustainability of this type of distributed research, and how knowledge gained from the earlier efforts can contribute to a continually learning health system.

Utilizing an integrated infrastructure for outcomes research: a systematic review

OBJECTIVE

To explore the ability of an integrated health information infrastructure to support outcomes research.

METHODS

A systematic review of articles published from 1983 to 2012 by Regenstrief Institute investigators using data from an integrated electronic health record infrastructure involving multiple provider organisations was performed. Articles were independently assessed and classified by study design, disease and other metadata including bibliometrics.

RESULTS

A total of 190 articles were identified. Diseases included cognitive, (16) cardiovascular, (16) infectious, (15) chronic illness (14) and cancer (12). Publications grew steadily (26 in the first decade vs. 100 in the last) as did the number of investigators (from 15 in 1983 to 62 in 2012). The proportion of articles involving non-Regenstrief authors also expanded from 54% in the first decade to 72% in the last decade. During this period, the infrastructure grew from a single health system into a health information exchange network covering more than 6 million patients. Analysis of journal and article metrics reveals high impact for clinical trials and comparative effectiveness research studies that utilised data available in the integrated infrastructure.

DISCUSSION

Integrated information infrastructures support growth in high quality observational studies and diverse collaboration consistent with the goals for the learning health system. More recent publications demonstrate growing external collaborations facilitated by greater access to the infrastructure and improved opportunities to study broader disease and health outcomes.

CONCLUSIONS

Integrated information infrastructures can stimulate learning from electronic data captured during routine clinical care but require time and collaboration to reach full potential.

Enhancing Vaccine Safety Capacity Globally: A Lifecycle Perspective

Major vaccine safety controversies have arisen in several countries beginning in the last decades of 20th century. Such periodic vaccine safety controversies are unlikely to go away in the near future as more national immunization programs mature with near elimination of target vaccine-preventable diseases that result in relative greater prominence of adverse events following immunizations, both true reactions and temporally coincidental events. There are several ways in which vaccine safety capacity can be improved to potentially mitigate the impact of future vaccine safety controversies. This paper aims to take a "lifecycle" approach, examining some potential pre- and post-licensure opportunities to improve vaccine safety, in both developed (specifically U.S. and Europe) and low- and middle-income countries.

Enhancing vaccine safety capacity globally: A lifecycle perspective

Major vaccine safety controversies have arisen in several countries beginning in the last decades of 20th century. Such periodic vaccine safety controversies are unlikely to go away in the near future as more national immunization programs mature with near elimination of target vaccine-preventable diseases that result in relative greater prominence of adverse events following immunizations, both true reactions and temporally coincidental events. There are several ways in which vaccine safety capacity can be improved to potentially mitigate the impact of future vaccine safety controversies. This paper aims to take a "lifecycle" approach, examining some potential pre- and post-licensure opportunities to improve vaccine safety, in both developed (specifically U.S. and Europe) and low- and middle-income countries.

Absence of venous thromboembolism risk following quadrivalent human papillomavirus vaccination, Vaccine Safety Datalink, 2008-2011

BACKGROUND

To investigate concerns about a potential association between quadrivalent human papillomavirus vaccination (HPV4) and venous thromboembolism (VTE), we conducted a self-controlled case series study in adolescents and young adults 9-26 years of age in the Vaccine Safety Datalink.

METHODS

We identified potential VTE cases diagnosed in 2008 through 2011 who had also received at least one HPV4 dose during that period. We confirmed each presumptive diagnosis by medical record review. We calculated incidence rate ratios (IRRs) and 95% confidence intervals (CI) to estimate the risk in the 1-60 day period following HPV4 exposure and in subsets of that period. IRRs were stratified by age, gender, hormonal contraceptive use, and recent surgery or trauma.

RESULTS

We identified 313 potential cases of VTE among HPV4 vaccinees, and 291 (93%) had sufficient medical records for review. Of these, we confirmed 156 (54%) cases. VTE was uncommon among males (n=3) and 9-12 year olds (n=4). Nearly all confirmed cases (97%) had at least one known risk factor for VTE, including hormonal contraceptive use, obesity, and hypercoagulability. Sixteen (10%) confirmed cases occurred in the 1-60 days following HPV4 exposure. The risk of VTE varied from 1.47 (95% CI: 0.47-4.64) in the 1-7 days following HPV4 exposure to 0.92 (95% CI: 0.54-1.57) in the 1-60 days following vaccination. It was not possible to calculate a stratified IRR for males due to small sample size; the other risk factors evaluated did not significantly affect the risk of VTE after HPV4 exposure.

CONCLUSION

The risk of developing VTE among 9- to 26-year-olds was not elevated following HPV4 exposure. Sample size limited our ability to rigorously evaluate potential effect modifiers, such as gender, through stratified analysis.

The Centers for Disease Control and Prevention's public health response to monitoring Tdap safety in pregnant women in the United States

In 2010, in response to a widespread pertussis outbreak and neonatal deaths, California became the first state to recommend routine administration of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine during pregnancy. In 2011, the Advisory Committee on Immunization Practices (ACIP) followed with a similar recommendation for Tdap vaccination during pregnancy for previously unvaccinated women. In 2012, this recommendation was expanded to include Tdap vaccination of every pregnant woman during each pregnancy. These recommendations were based on urgent public health needs and available evidence on the safety of other inactivated vaccines during pregnancy. However, there were limited data on the safety of Tdap during pregnancy. In response to the new ACIP recommendations, the Centers for Disease Control and Prevention (CDC) implemented ongoing collaborative studies to evaluate whether vaccination with Tdap during pregnancy adversely affects the health of mothers and their offspring and provide the committee with regular updates. The current commentary describes the public health actions taken by CDC to respond to the ACIP recommendation to study and monitor the safety of Tdap vaccines in pregnant women and describes the current state of knowledge on the safety of Tdap vaccines in pregnant women. Data from the various monitoring activities support the safety of Tdap use during pregnancy.

Demographic characteristics of members of the Vaccine Safety Datalink (VSD): A comparison with the United States population

BACKGROUND

The Vaccine Safety Datalink (VSD) is a collaboration between CDC and nine integrated health care systems that serves as a cornerstone of US post-licensure vaccine safety monitoring. Given concerns that potential differences between the insured VSD population and the US population could limit the generalizability of VSD study findings, we performed a comparison of the demographic characteristics between the two populations.

METHODS

We collected data from medical records and administrative files at VSD sites in 2010 to compare sex, age, race, ethnicity, income, and educational attainment to the 2010 US Census population. We also compared data on the 2012 VSD Medicaid population to 2012 US Medicaid data.

RESULTS

The VSD population included over eight million individuals in 2010, which represented 2.6% of the total US population. All major demographic groups were represented in the VSD. We found no major differences in comparing sex, race, ethnicity, and educational attainment between the VSD and the US population. Middle income populations were comparable between the VSD and the US. While the percentage of lower income populations was less in the VSD compared to the US, the VSD had over two million individuals in this group. Additionally, there were over 600,000 Medicaid members in the VSD in 2012, which represented 1.1% of the US Medicaid population.

CONCLUSIONS

We found that the VSD population is representative of the general US population on several key demographic and socioeconomic variables. Despite a few specific groups being underrepresented in the VSD compared to the US, the absolute number of VSD members is large enough to ensure significant representation of these groups in vaccine safety studies that use VSD data.

Safety monitoring in the Vaccine Adverse Event Reporting System (VAERS)

The Centers for Disease Control and Prevention (CDC) and the U.S. Food and Drug Administration (FDA) conduct post-licensure vaccine safety monitoring using the Vaccine Adverse Event Reporting System (VAERS), a spontaneous (or passive) reporting system. This means that after a vaccine is approved, CDC and FDA continue to monitor safety while it is distributed in the marketplace for use by collecting and analyzing spontaneous reports of adverse events that occur in persons following vaccination. Various methods and statistical techniques are used to analyze VAERS data, which CDC and FDA use to guide further safety evaluations and inform decisions around vaccine recommendations and regulatory action. VAERS data must be interpreted with caution due to the inherent limitations of passive surveillance. VAERS is primarily a safety signal detection and hypothesis generating system. Generally, VAERS data cannot be used to determine if a vaccine caused an adverse event. VAERS data interpreted alone or out of context can lead to erroneous conclusions about cause and effect as well as the risk of adverse events occurring following vaccination. CDC makes VAERS data available to the public and readily accessible online. We describe fundamental vaccine safety concepts, provide an overview of VAERS for healthcare professionals who provide vaccinations and might want to report or better understand a vaccine adverse event, and explain how CDC and FDA analyze VAERS data. We also describe strengths and limitations, and address common misconceptions about VAERS. Information in this review will be helpful for healthcare professionals counseling patients, parents, and others on vaccine safety and benefit-risk balance of vaccination.

Risk of Herpes Zoster and Disseminated Varicella Zoster in Patients Taking Immunosuppressant Drugs at the Time of Zoster Vaccination

OBJECTIVE

To determine the risks associated with zoster vaccine when administered to patients taking immunosuppressant medications.

PATIENTS AND METHODS

Patients enrolled in 1 of 7 managed care organizations affiliated with the Vaccine Safety Datalink between January 1, 2006, and December 31, 2009, were eligible. The exposure of interest was zoster vaccination in patients with current or remote immunosuppressant drug use. The primary outcomes were disseminated varicella zoster virus (VZV) and herpes zoster in the 42 days after vaccination. Automated data were collected on immunosuppressant drugs and baseline medical conditions. A logistic regression model using inverse probability treatment weights was used to estimate the odds of developing VZV or herpes zoster.

RESULTS

A total of 14,554 individuals had an immunosuppressant medication dispensed around the time of vaccination, including 4826 with current use and 9728 with remote use. Most patients were taking low-dose corticosteroids. No cases of disseminated VZV were found in the current or remote users. The risk of herpes zoster was elevated in the 42 days after vaccination in current vs remote users (adjusted odds ratio, 2.99; 95% CI, 1.58-5.70).

CONCLUSION

We found that patients taking immunosuppressant medications at the time of vaccination had a modest increased risk of herpes zoster in the 42 days after vaccination. The development of herpes zoster within 42 days after vaccination suggests that this is more likely due to reactivation of latent zoster virus than dissemination of the vaccine-derived varicella virus. These findings support the current zoster vaccination guidelines.

Evaluating efficiency and statistical power of self-controlled case series and self-controlled risk interval designs in vaccine safety

The self-controlled case series (SCCS) and self-controlled risk interval (SCRI) designs have recently become widely used in the field of post-licensure vaccine safety monitoring to detect potential elevated risks of adverse events following vaccinations. The SCRI design can be viewed as a subset of the SCCS method in that a reduced comparison time window is used for the analysis. Compared to the SCCS method, the SCRI design has less statistical power due to fewer events occurring in the shorter control interval. In this study, we derived the asymptotic relative efficiency (ARE) between these two methods to quantify this loss in power in the SCRI design. The equation is formulated as [Formula: see text] (a: control window-length ratio between SCRI and SCCS designs; b: ratio of risk window length and control window length in the SCCS design; and [Formula: see text]: relative risk of exposed window to control window). According to this equation, the relative efficiency declines as the ratio of control-period length between SCRI and SCCS methods decreases, or with an increase in the relative risk [Formula: see text]. We provide an example utilizing data from the Vaccine Safety Datalink (VSD) to study the potential elevated risk of febrile seizure following seasonal influenza vaccine in the 2010-2011 season.

Advanced Clinical Decision Support for Vaccine Adverse Event Detection and Reporting

BACKGROUND

Reporting of adverse events (AEs) following vaccination can help identify rare or unexpected complications of immunizations and aid in characterizing potential vaccine safety signals. We developed an open-source, generalizable clinical decision support system called Electronic Support for Public Health-Vaccine Adverse Event Reporting System (ESP-VAERS) to assist clinicians with AE detection and reporting.

METHODS

ESP-VAERS monitors patients' electronic health records for new diagnoses, changes in laboratory values, and new allergies following vaccinations. When suggestive events are found, ESP-VAERS sends the patient's clinician a secure electronic message with an invitation to affirm or refute the message, add comments, and submit an automated, prepopulated electronic report to VAERS. High-probability AEs are reported automatically if the clinician does not respond. We implemented ESP-VAERS in December 2012 throughout the MetroHealth System, an integrated healthcare system in Ohio. We queried the VAERS database to determine MetroHealth's baseline reporting rates from January 2009 to March 2012 and then assessed changes in reporting rates with ESP-VAERS.

RESULTS

In the 8 months following implementation, 91 622 vaccinations were given. ESP-VAERS sent 1385 messages to responsible clinicians describing potential AEs. Clinicians opened 1304 (94.2%) messages, responded to 209 (15.1%), and confirmed 16 for transmission to VAERS. An additional 16 high-probability AEs were sent automatically. Reported events included seizure, pleural effusion, and lymphocytopenia. The odds of a VAERS report submission during the implementation period were 30.2 (95% confidence interval, 9.52-95.5) times greater than the odds during the comparable preimplementation period.

CONCLUSIONS

An open-source, electronic health record-based clinical decision support system can increase AE detection and reporting rates in VAERS.

Safety of human papillomavirus vaccines: a review

INTRODUCTION

Between 2006 and 2009, two different human papillomavirus virus (HPV) vaccines were licensed for use: a quadrivalent (qHPVv) and a bivalent (bHPVv) vaccine. Since 2008, HPV vaccination programmes have been implemented in the majority of the industrialized countries. Since 2013, HPV vaccination has been part of the national programs of 66 countries including almost all countries in North America and Western Europe. Despite all the efforts made by individual countries, coverage rates are lower than expected. Vaccine safety represents one of the main concerns associated with the lack of acceptance of HPV vaccination both in the European Union/European Economic Area and elsewhere.

AREAS COVERED

Safety data published on bivalent and quadrivalent HPV vaccines, both in pre-licensure and post-licensure phase, are reviewed.

EXPERT OPINION

Based on the latest scientific evidence, both HPV vaccines seem to be safe. Nevertheless, public concern and rumors about adverse events (AE) represent an important barrier to overcome in order to increase vaccine coverage. Passive surveillance of AEs is an important tool for detecting safety signals, but it should be complemented by activities aimed at assessing the real cause of all suspect AEs. Improved vaccine safety surveillance is the first step for effective communication based on scientific evidence.

A comparison of active adverse event surveillance systems worldwide

Post-marketing drug surveillance for adverse drug events (ADEs) has typically relied on spontaneous reporting. Recently, regulatory agencies have turned their attention to more preemptive approaches that use existing data for surveillance. We conducted an environmental scan to identify active surveillance systems worldwide that use existing data for the detection of ADEs. We extracted data about the systems' structures, data, and functions. We synthesized the information across systems to identify common features of these systems. We identified nine active surveillance systems. Two systems are US based-the FDA Sentinel Initiative (including both the Mini-Sentinel Initiative and the Federal Partner Collaboration) and the Vaccine Safety Datalink (VSD); two are Canadian-the Canadian Network for Observational Drug Effect Studies (CNODES) and the Vaccine and Immunization Surveillance in Ontario (VISION); and two are European-the Exploring and Understanding Adverse Drug Reactions by Integrative Mining of Clinical Records and Biomedical Knowledge (EU-ADR) Alliance and the Vaccine Adverse Event Surveillance and Communication (VAESCO). Additionally, there is the Asian Pharmacoepidemiology Network (AsPEN) and the Shanghai Drug Monitoring and Evaluative System (SDMES). We identified two systems in the UK-the Vigilance and Risk Management of Medicines (VRMM) Division and the Drug Safety Research Unit (DSRU), an independent academic unit. These surveillance systems mostly use administrative claims or electronic medical records; most conduct pharmacovigilance on behalf of a regulatory agency. Either a common data model or a centralized model is used to access existing data. The systems have been built using national data alone or via partnership with other countries. However, active surveillance systems using existing data remain rare. North America and Europe have the most population coverage; with Asian countries making good advances.

The complementary roles of Phase 3 trials and post-licensure surveillance in the evaluation of new vaccines

Vaccines have led to significant reductions in morbidity and saved countless lives from many infectious diseases and are one of the most important public health successes of the modern era. Both vaccines' effectiveness and safety are keys for the success of immunisation programmes. The role of post-licensure surveillance has become increasingly recognised by regulatory authorities in the overall vaccine development process. Safety, purity, and effectiveness of vaccines are carefully assessed before licensure, but some safety and effectiveness aspects need continuing monitoring after licensure; Post-marketing activities are a necessary complement to pre-licensure activities for monitoring vaccine quality and to inform public health programmes. In the recent past, the availability of large databases together with data-mining and cross-linkage techniques have significantly improved the potentialities of post-licensure surveillance. The scope of this review is to present challenges and opportunities offered by vaccine post-licensure surveillance. While pre-licensure activities form the foundation for the development of effective and safe vaccines, post-licensure monitoring and assessment, are necessary to assure that vaccines are effective and safe when translated in real world settings. Strong partnerships and collaboration at an international level between different stakeholders is necessary for finding and optimally allocating resources and establishing robust post-licensure processes.

Canadian vaccine research networks: Vaccine safety resources for Canada

The Public Health Agency of Canada / Canadian Institutes of Health Research Influenza Research Network (PCIRN), established in 2009 to undertake evaluative research to inform public health decision making in Canada, is now being replaced by the Canadian Immunization Research Network (CIRN), which will retain the mandate of PCIRN but expand it to all vaccines including influenza vaccine. CIRN is organized as a network of networks focusing on undertaking research in the areas of vaccine safety, adverse events following immunization (AEFIs), vaccine hesitancy, vaccine effectiveness, and vaccine coverage. CIRN's networks include: a clinical trial network; a laboratory network; a modelling and economics network; a network of social science and humanities researchers; a vaccine safety surveillance network; a hospital-based surveillance network; a clinic network to evaluate serious AEFIs; and a network that links vaccine research capacity in provincial health agencies and departments. PCIRN has contributed to Canada's vaccine safety surveillance system and has facilitated the translation of safety research into policy. Vaccine safety surveillance and research will remain a focus of the newly formed Canadian Immunization Research Network.

Best vaccination practice and medically attended injection site events following deltoid intramuscular injection

Analysis of medically attended injection site events data provides a vehicle to appreciate the inadequacies of vaccination practice for deltoid intramuscular injection and to develop best practice procedures. These data can be divided into 3 groups; nerve palsies, musculoskeletal injuries and cutaneous reactions and reflect inappropriate site of injection, needle over or under penetration, local sepsis and vascular complications. The aim of this review is to formulate best vaccination practice procedures for deltoid intramuscular injection of vaccines through the collation and analysis of medically attended injection site events.

Using winter 2009-2010 to assess the accuracy of methods which estimate influenza-related morbidity and mortality

We used the winter of 2009-2010, which had minimal influenza circulation due to the earlier 2009 influenza A(H1N1) pandemic, to test the accuracy of ecological trend methods used to estimate influenza-related deaths and hospitalizations. We aggregated weekly counts of person-time, all-cause deaths, and hospitalizations for pneumonia/influenza and respiratory/circulatory conditions from seven healthcare systems. We predicted the incidence of the outcomes during the winter of 2009-2010 using three different methods: a cyclic (Serfling) regression model, a cyclic regression model with viral circulation data (virological regression), and an autoregressive, integrated moving average model with viral circulation data (ARIMAX). We compared predicted non-influenza incidence with actual winter incidence. All three models generally displayed high accuracy, with prediction errors for death ranging from -5% to -2%. For hospitalizations, errors ranged from -10% to -2% for pneumonia/influenza and from -3% to 0% for respiratory/circulatory. The Serfling and virological models consistently outperformed the ARIMAX model. The three methods tested could predict incidence of non-influenza deaths and hospitalizations during a winter with negligible influenza circulation. However, meaningful mis-estimation of the burden of influenza can still result with outcomes for which the contribution of influenza is low, such as all-cause mortality.

Evaluation of the association of maternal pertussis vaccination with obstetric events and birth outcomes

IMPORTANCE

In 2010, due to a pertussis outbreak and neonatal deaths, the California Department of Health recommended that the tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine (Tdap) be administered during pregnancy. Tdap is now recommended by the Advisory Committee on Immunization Practices for all pregnant women, preferably between 27 and 36 weeks' gestation. Limited data exist on Tdap safety during pregnancy.

OBJECTIVE

To evaluate whether maternal Tdap vaccination during pregnancy is associated with increased risks of adverse obstetric events or adverse birth outcomes.

DESIGN AND SETTING

Retrospective, observational cohort study using administrative health care databases from 2 California Vaccine Safety Datalink sites.

PARTICIPANTS AND EXPOSURES

Of 123,494 women with singleton pregnancies ending in a live birth between January 1, 2010, and November 15, 2012, 26,229 (21%) received Tdap during pregnancy and 97,265 did not.

MAIN OUTCOMES AND MEASURES

Risks of small-for-gestational-age (SGA) births (<10th percentile), chorioamnionitis, preterm birth (<37 weeks' gestation), and hypertensive disorders of pregnancy were evaluated. Relative risk (RR) estimates were adjusted for site, receipt of another vaccine during pregnancy, and propensity to receive Tdap during pregnancy. Cox regression was used for preterm delivery, and Poisson regression for other outcomes.

RESULTS

Vaccination was not associated with increased risks of adverse birth outcomes: crude estimates for preterm delivery were 6.3% of vaccinated and 7.8% of unvaccinated women (adjusted RR, 1.03; 95% CI, 0.97-1.09); 8.4% of vaccinated and 8.3% of unvaccinated had an SGA birth (adjusted RR, 1.00; 95% CI, 0.96-1.06). Receipt of Tdap before 20 weeks was not associated with hypertensive disorder of pregnancy (adjusted RR, 1.09; 95% CI, 0.99-1.20); chorioamnionitis was diagnosed in 6.1% of vaccinated and 5.5% of unvaccinated women (adjusted RR, 1.19; 95% CI, 1.13-1.26).

CONCLUSIONS AND RELEVANCE

In this cohort of women with singleton pregnancies that ended in live birth, receipt of Tdap during pregnancy was not associated with increased risk of hypertensive disorders of pregnancy or preterm or SGA birth, although a small but statistically significant increased risk of chorioamnionitis diagnosis was observed.

Childhood vaccines and Kawasaki disease, Vaccine Safety Datalink, 1996-2006

BACKGROUND

Kawasaki disease is a childhood vascular disorder of unknown etiology. Concerns have been raised about vaccinations being a potential risk factor for Kawasaki disease.

METHODS

Data from the Vaccine Safety Datalink were collected on children aged 0-6 years at seven managed care organizations across the United States. Defining exposure as one of several time periods up to 42 days after vaccination, we conducted Poisson regressions controlling for age, sex, season, and managed care organization to determine if rates of physician-diagnosed and verified Kawasaki disease were elevated following vaccination compared to rates during all unexposed periods. We also performed case-crossover analyses to control for unmeasured confounding.

RESULTS

A total of 1,721,186 children aged 0-6 years from seven managed care organizations were followed for a combined 4,417,766 person-years. The rate of verified Kawasaki disease was significantly lower during the 1-42 days after vaccination (rate ratio=0.50, 95% CL=0.27-0.92) and 8-42 days after vaccination (rate ratio=0.45, 95% CL=0.22-0.90) compared to rates during unexposed periods. Breaking down the analysis by vaccination category did not identify a subset of vaccines which was solely responsible for this association. The case-crossover analyses revealed that children with Kawasaki disease had lower rates of vaccination in the 42 days prior to symptom onset for both physician-diagnosed Kawasaki disease (rate ratio=0.79, 95% CL=0.64-0.97) and verified Kawasaki disease (rate ratio=0.38, 95% CL=0.20-0.75).

CONCLUSIONS

Childhood vaccinations' studied did not increase the risk of Kawasaki disease; conversely, vaccination was associated with a transient decrease in Kawasaki disease incidence. Verifying and understanding this potential protective effect could yield clues to the underlying etiology of Kawasaki disease.

Narcolepsy and influenza A(H1N1) pandemic 2009 vaccination in the United States

OBJECTIVE

To assess the occurrence of narcolepsy after influenza vaccines used in the United States that contained the influenza A(H1N1)pdm09 virus strain.

METHODS

A population-based cohort study in the Vaccine Safety Datalink with an annual population of more than 8.5 million people. All persons younger than 30 years who received a 2009 pandemic or a 2010-2011 seasonal influenza vaccine were identified. Their medical visit history was searched for a first-ever occurrence of an ICD-9 narcolepsy diagnosis code through the end of 2011. Chart review was done to confirm the diagnosis and determine the date of symptom onset. Cases were patients who met the International Classification of Sleep Disorders, 2nd edition, narcolepsy diagnostic criteria. We compared the observed number of cases after vaccination to the number expected to occur by chance alone.

RESULTS

The number vaccinated with 2009 pandemic vaccine was 650,995 and with 2010-2011 seasonal vaccine was 870,530. Among these patients, 70 had a first-ever narcolepsy diagnosis code after vaccination, of which 16 had a chart-confirmed incident diagnosis of narcolepsy. None had their symptom onset during the 180 days after receipt of a 2009 pandemic vaccine compared with 6.52 expected, and 2 had onset after a 2010-2011 seasonal vaccine compared with 8.83 expected.

CONCLUSIONS

Influenza vaccines containing the A(H1N1)pdm09 virus strain used in the United States were not associated with an increased risk of narcolepsy. Vaccination with the influenza A(H1N1)pdm09 vaccine viral antigens does not appear to be sufficient by itself to increase the incidence of narcolepsy in a population.

Adolescent Premature Ovarian Insufficiency Following Human Papillomavirus Vaccination: A Case Series Seen in General Practice

Three young women who developed premature ovarian insufficiency following quadrivalent human papillomavirus (HPV) vaccination presented to a general practitioner in rural New South Wales, Australia. The unrelated girls were aged 16, 16, and 18 years at diagnosis. Each had received HPV vaccinations prior to the onset of ovarian decline. Vaccinations had been administered in different regions of the state of New South Wales and the 3 girls lived in different towns in that state. Each had been prescribed the oral contraceptive pill to treat menstrual cycle abnormalities prior to investigation and diagnosis. Vaccine research does not present an ovary histology report of tested rats but does present a testicular histology report. Enduring ovarian capacity and duration of function following vaccination is unresearched in preclinical studies, clinical and postlicensure studies. Postmarketing surveillance does not accurately represent diagnoses in adverse event notifications and can neither represent unnotified cases nor compare incident statistics with vaccine course administration rates. The potential significance of a case series of adolescents with idiopathic premature ovarian insufficiency following HPV vaccination presenting to a general practice warrants further research. Preservation of reproductive health is a primary concern in the recipient target group. Since this group includes all prepubertal and pubertal young women, demonstration of ongoing, uncompromised safety for the ovary is urgently required. This matter needs to be resolved for the purposes of population health and public vaccine confidence.

Rapid online identification of adverse events after influenza immunization in children by PCIRN's National Ambulatory Network

BACKGROUND

A National Ambulatory Network was created in 2009 to rapidly assess the safety of influenza vaccines. In 2012, the network was expanded to monitor the safety of live attenuated influenza vaccine and trivalent inactivated influenza vaccine in children.

METHODS

We used an online survey administered 7 days after influenza immunization to track new or exacerbated health problems that required medical consultation or prevented daily activities. Parents of immunized children completed the survey. Reported adverse events were followed up by telephone within 48 hours of the online report. A sample of nonresponders was contacted by telephone to ensure the online responder group was representative. Event rates after the 2 influenza vaccines were compared.

RESULTS

A total of 1230 parents completed an online or telephone survey, for a participation rate of 83%: 72% responded online and an additional 11% were reached by telephone. The rate of severe events in children immunized with an influenza vaccine was 4.7% (3.5-5.9%). The frequency and types of events reported were similar between online and telephone reports. Reported rates of severe events were similar after trivalent inactivated influenza or live attenuated influenza vaccine (4.0% vs. 5.1%, respectively). The online survey was easy to access and understand. Most respondents (94%) would participate next year.

CONCLUSIONS

The rate and type of adverse events after immunization with trivalent inactivated influenza versus live attenuated influenza vaccine were similar and did not vary by reporting process (online vs. telephone). The electronic surveillance methodology provided rapid vaccine safety data in children. The electronic survey methodology was acceptable and feasible.

Receipt of pertussis vaccine during pregnancy across 7 Vaccine Safety Datalink sites

OBJECTIVE

In response to widespread pertussis outbreaks and infant deaths, in 2010, the California Department of Health (CDPH) and in 2011 the Advisory Committee on Immunization Practices (ACIP) advised that the tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccine be administered during pregnancy. The goals of this study were to describe Tdap coverage among pregnant women following these recommendations.

METHODS

In this observational cohort study, we utilized electronic medical record and claims data from seven Vaccine Safety Datalink sites to identify pregnancies and Tdap administrations. All Tdap doses were classified as pre-pregnancy, during pregnancy or post-pregnancy/postpartum. For pregnancies ending in a live birth, we evaluated factors associated with Tdap vaccination.

RESULTS

Among 289,141 live births at the California VSD sites, receipt of Tdap during pregnancy increased substantially in the years 2010, 2011, and 2012, when coverage was 15.9, 30.0 and 19.5%, respectively. Among 82,398 women with live births at the Oregon, Washington, Colorado, Wisconsin and Minnesota VSD sites, receipt of Tdap during pregnancy first increased in 2012, at 16.0%. Women receiving early prenatal care and other vaccine(s) during pregnancy had higher Tdap coverage.

CONCLUSION

We observed substantial increases in Tdap coverage during pregnancy following CDPH and ACIP recommendations.

The Vaccine Safety Datalink: successes and challenges monitoring vaccine safety

The Vaccine Safety Datalink (VSD) is a collaborative project between the Centers for Disease Control and Prevention (CDC) and 9 health care organizations. Established in 1990, VSD is a vital resource informing policy makers and the public about the safety of vaccines used in the United States. Large linked databases are used to identify and evaluate adverse events in over 9 million individuals annually. VSD generates rapid, important safety assessments for both routine vaccinations and emergency vaccination campaigns. VSD monitors safety of seasonal influenza vaccines in near-real time, and provided essential information on the safety of influenza A (H1N1) 2009 monovalent vaccine during the recent pandemic. VSD investigators have published important studies demonstrating that childhood vaccines are not associated with autism or other developmental disabilities. VSD prioritizes evaluation of new vaccines; searches for possible unusual health events after vaccination; monitors vaccine safety in pregnant women; and has pioneered development of biostatistical research methods.

Orphan therapies: making best use of postmarket data

BACKGROUND

Postmarket surveillance of the comparative safety and efficacy of orphan therapeutics is challenging, particularly when multiple therapeutics are licensed for the same orphan indication. To make best use of product-specific registry data collected to fulfill regulatory requirements, we propose the creation of a distributed electronic health data network among registries. Such a network could support sequential statistical analyses designed to detect early warnings of excess risks. We use a simulated example to explore the circumstances under which a distributed network may prove advantageous.

METHODS

We perform sample size calculations for sequential and non-sequential statistical studies aimed at comparing the incidence of hepatotoxicity following initiation of two newly licensed therapies for homozygous familial hypercholesterolemia. We calculate the sample size savings ratio, or the proportion of sample size saved if one conducted a sequential study as compared to a non-sequential study. Then, using models to describe the adoption and utilization of these therapies, we simulate when these sample sizes are attainable in calendar years. We then calculate the analytic calendar time savings ratio, analogous to the sample size savings ratio. We repeat these analyses for numerous scenarios.

KEY RESULTS

Sequential analyses detect effect sizes earlier or at the same time as non-sequential analyses. The most substantial potential savings occur when the market share is more imbalanced (i.e., 90% for therapy A) and the effect size is closest to the null hypothesis. However, due to low exposure prevalence, these savings are difficult to realize within the 30-year time frame of this simulation for scenarios in which the outcome of interest occurs at or more frequently than one event/100 person-years.

CONCLUSIONS

We illustrate a process to assess whether sequential statistical analyses of registry data performed via distributed networks may prove a worthwhile infrastructure investment for pharmacovigilance.

Monovalent H1N1 influenza vaccine safety in pregnant women, risks for acute adverse events

OBJECTIVE

To assess risks for acute adverse events and pregnancy complications in pregnant women following monovalent 2009 H1N1 inactivated influenza (MIV) vaccination.

METHODS

Within the Vaccine Safety Datalink, we compared rates of pre-specified medically attended events (MAE) occurring within 42 days of MIV vaccination to those occurring in matched cohorts that at the same gestational age were either unvaccinated or received seasonal trivalent inactivated influenza (TIV) vaccine. Using generalized estimating equation method, with a Poisson distribution and log link, we calculated adjusted incident rate ratios (AIRR).

RESULTS

Among 9349 women receiving MIV in any trimester, only one MAE occurred 0-3 days following MIV, an allergic reaction. No cases of Guillain-Barré syndrome, Bell's palsy, or transverse myelitis occurred 1-42 days after MIV. Compared to women receiving TIV and to unvaccinated women, risks for acute MAEs were not increased following MIV for any outcome. Hyperemesis was the most common adverse event in the MIV, TIV, and unvaccinated groups, occurring at a rate of about 4% over a 42-day period in all groups. Over a 42-day window, among all groups, incident gestational diabetes occurred at a rate of 3% and thrombocytopenia occurred at a rate of approximately 0.3%. Among women receiving MIV during pregnancy, increased risks for these and other less common obstetric events were not detected.

CONCLUSION

In this large cohort of pregnant women no acute safety signals were identified within 6 weeks of receipt of MIV.