Demographic characteristics of members of the Vaccine Safety Datalink (VSD): A comparison with the United States population
Introduction
Vaccines are considered one of the most important public health successes of the century, and vaccine safety monitoring is a critical component to any vaccination program [1], [2]. The Vaccine Safety Datalink (VSD) is a collaboration between the Centers for Disease Control and Prevention (CDC) and nine integrated health care systems (sites) that conducts post-marketing vaccine safety evaluations on approximately 3% of the United States (US) population [3], [4]. The VSD provides essential vaccine safety data to stakeholders (health care providers, public health officials, and the public) and can inform national immunization policy.
The VSD has played a significant role in vaccine safety monitoring in the United States. Important public health investigations conducted by the VSD include studies that have found associations between rotavirus vaccine and intussusception [5], [6], [7], and febrile seizures and vaccines [8], [9], as well as a lack of association between vaccines and neurodevelopmental disorders [10], [11]. The VSD has also conducted studies on the safety of influenza and Tdap vaccination in pregnant women [12], [13], [14]. A potential limitation of VSD data is a perceived lack of generalizability between the insured VSD population and the more socioeconomically diverse US population. This limitation was commented upon in a recent Institute of Medicine (IOM) report on the safety of the childhood immunization schedule [15]. Differences in education, income, or socioeconomic status may translate to differences in health care seeking behaviors [16], [17], access to healthcare, and differences in adverse events following vaccination [18].
While one study compared the demographic characteristics of one VSD site to its state [19], and other studies have examined VSD vaccination coverage rates and mortality rates relative to those of the US [20], [21], a comprehensive comparison of the demographic characteristics of the entire VSD population with the US population has not been previously conducted. The prior vaccination coverage study showed that the VSD generally had higher vaccination coverage in children compared to the US population [20]. The goal of this study was to compare the VSD population to the US population in order to examine the generalizability of VSD findings to the broader US population.
Section snippets
Methods
VSD data are provided by nine sites in diverse geographical locations across the US. Of these, six infrastructure sites provide data on a continuous basis: Kaiser Permanente of Southern California (SCK), Kaiser Permanente of Northern California (NCK), Kaiser Permanente Northwest (NWK), Group Health Cooperative (GHC), Kaiser Permanente of Colorado (KPC), and Marshfield Clinic Research Foundation (MFC). Three additional sites can provide data for specific studies: Health Partners Research
Results
Among the VSD infrastructure sites in 2010, there were 8,085,329 people enrolled (Table 1), which represented 2.6% of the total US population. The distribution by sex was similar between the VSD and US populations. The age distributions were also similar between the two groups; however, the 55 to 59 year age group and 60 to 64 year age group were each slightly overrepresented in the VSD (7.2% in the VSD vs. 4.8% in the US and 6.2% in the VSD vs. 3.8% in the US respectively).
When comparing race
Discussion
Post-licensure vaccine safety data monitoring is a crucial part of a successful vaccination program. As the VSD is a network that is used for high impact vaccine safety studies, it is important to know how its population may be different from that of the United States. Overall, we found that the VSD population is representative of the US population for a number of characteristics. Apart from small differences in age distribution, race/ethnicity, income and education levels of the overall
Conclusions
Our study shows that overall, the VSD well represents the US population with regard to sex, race, ethnicity, income, education and Medicare populations. Despite some differences that may affect specific studies, our data suggest findings from studies conducted in the VSD population are largely generalizable to the US population.
Contributors
LS, NLM, and RL were involved in collecting data and writing the manuscript. All authors contributed to designing the study, interpreting the data, revising the draft, and approved the manuscript for submission.
Funding
The project described was supported by the Centers for Disease Control and Prevention (CDC) and Award Number T32AI074492 from the National Institute of Allergy and Infectious Diseases. The content is solely the responsibility of the authors and does not necessarily represent the official policy or position of the Centers for Disease Control and Prevention, the National Institute of Allergy and Infectious Diseases or the National Institutes of Health.
Conflict of interest
All VSD authors are funded by the Centers for Disease Control and prevention. Dr. Sukumaran received research support from the National Institutes of Health. Dr. Naleway received research support from GlaxoSmithKline and Pfizer.
Acknowledgments
We gratefully acknowledge James Donahue, DVM, PhD, from the Marshfield Clinic for his review of the manuscript and all of the Vaccine Safety Datalink data managers for assistance in collecting data for this study.
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