Background Mortality Rates Key to Accurate Reporting of Vaccine Safety Risks

 Collaborative study utilizing Vaccine Safety Datalink published in the American Journal of Preventive Medicine

San Diego, CA, June 11, 2013

In a study using the Vaccine Safety Datalink (VSD), investigators analyzed four years of data and determined that background mortality rates (rates of death irrespective of cause) are crucial in interpreting the numbers of deaths following vaccination. The VSD mortality rate following immunization is lower than the general US population mortality rate, and the causes of death are similar. These background rates can be used in communications to the public about vaccine safety risks, reports the American Journal of Preventive Medicine.

Public concern about deaths and other adverse events following immunization can disrupt immunization programs and lead to an increase in vaccine-preventable disease.

"Determining the baseline mortality rate in a vaccinated population is necessary to be able to identify any unusual increases in deaths following vaccine administration," says lead investigator Natalie L. McCarthy, MPH, an epidemiologist at the Centers for Disease Control and Prevention (CDC). VSD mortality rates demonstrate a healthy vaccinee effect where rates were lowest in the days immediately following vaccination, most apparent in the older age groups. The healthy vaccinee effect suggests an avoidance or delay of vaccination when an individual is sick, leading to lower background rates of illness or mortality immediately following vaccination.

"Although there is currently no evidence to support a causal relationship between vaccinations and death, this study provides background mortality rates following vaccination to be used as a baseline when examining the safety profiles of new vaccines and during mass immunization campaigns," adds McCarthy.

Investigators from the Centers for Disease Control and Prevention (CDC) and ten healthcare organizations (sites) that conduct vaccine safety research and surveillance, report on background mortality rates, describe causes of death following vaccination, and examine mortality rates by age, gender, and number of days following vaccination using data recorded in the Vaccine Safety Datalink (VSD).

The VSD is a collaborative project between the CDC and these sites and captures comprehensive medical and immunization histories for over ten million people annually, or approximately three percent of the US population. It uses administrative and other sources at each site to gather data on enrollee demographics, vaccination, and medical outcomes, including mortality. The VSD conducts planned immunization safety studies following the introduction of new vaccines or changes in the immunization schedule, as well as timely investigations of hypotheses that arise from review of medical literature, clinical case reports, or reports from the Vaccine Adverse Event Reporting System (VAERS), a national passive adverse-event reporting system.

Analyses were conducted in 2012. Mortality rates were calculated for deaths occurring one, seven, 30 and 60 days following vaccination between January 1, 2005 and December 31, 2008. The analyses were stratified by age and sex. Causes of death were examined, and findings were compared with National Center for Health Statistics (NCHS) data.

Among 13,033,274 vaccinated people, 15,455 deaths occurred within 60 days following vaccination. The rates were highest in people of age 85 years and older, and increased over the period following vaccination. Eleven of the 15 leading causes of death in the VSD and NCHS overlap in both systems, and the top four causes of death were the same in both systems.

This study was supported by the Vaccine Safety Datalink contract with America's Health Insurance Plans, funded by the CDC. "The Vaccine Safety Datalink provides a vital infrastructure for monitoring vaccine safety, and generating background mortality rates is another asset of the vaccine safety system. Similar analyses should be conducted when new vaccines are added to the CDC's Advisory Committee on Immunization Practices recommended schedule, and would also be useful in other populations, including vulnerable subpopulations such as pregnant women and people with underlying health conditions," says McCarthy.

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Notes for Editors
"Mortality Rates and Cause-of-Death Patterns in a Vaccinated Population," by Natalie McCarthy, MPH; Eric Weintraub, MPH; Claudia Vellozzi, MD, MPH; Jonathan Duffy, MD, MPH; Julianne Gee, MPH; James G Donahue, DVM, PhD; Michael L Jackson, PhD, MPH; Grace M Lee, MD, MPH; Jason Glanz, PhD; Roger Baxter, MD; Marlene M Lugg, DrPH.; Allison Naleway, PhD; Saad B Omer, MBBS, MPH, PhD; Cynthia Nakasato, MD; Gabriela Vazquez-Benitez, MS, PhD; and Frank DeStefano, MD, MPH (DOI: 10.1016/j.amepre.2013.02.020). American Journal of Preventive Medicine, Volume 45, Issue 1 (July 2013), published by Elsevier.

Full text of the articles is available to credentialed journalists upon request; contact Brianna Lee at +1 858 534 9407 or eAJPM@ucsd.edu. Journalists wishing to interview the authors should contact Melissa Dankel, Public Affairs Specialist, Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, at +1 404 639 4718, +1 404 903 0241 (cell) or mdankel@cdc.gov.

About the American Journal of Preventive Medicine
The American Journal of Preventive Medicine (www.ajpmonline.org) is the official journal of The American College of Preventive Medicine (www.acpm.org) and the Association for Prevention Teaching and Research (http://www.aptrweb.org/). It publishes articles in the areas of prevention research, teaching, practice and policy. Original research is published on interventions aimed at the prevention of chronic and acute disease and the promotion of individual and community health. The journal features papers that address the primary and secondary prevention of important clinical, behavioral and public health issues such as injury and violence, infectious disease, women's health, smoking, sedentary behaviors and physical activity, nutrition, diabetes, obesity, and alcohol and drug abuse. Papers also address educational initiatives aimed at improving the ability of health professionals to provide effective clinical prevention and public health services. The journal also publishes official policy statements from the two co-sponsoring organizations, health services research pertinent to prevention and public health, review articles, media reviews, and editorials.

The American Journal of Preventive Medicine, with an Impact Factor of 4.044, is ranked 12th out of 157 Public, Environmental and Occupational Health titles and 17th out of 153 General & Internal Medicine titles according to the 2011 Journal Citation Reports® published by Thomson Reuters.

About Elsevier

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Media contact
Brianna Lee
+1 858 534 9407
eAJPM@ucsd.edu