Adverse events associated with smallpox vaccination in the United States, January-October 2003.
BACKGROUND
On January 24, 2003, the US Department of Health and Human Services (DHHS) implemented a preparedness program in which smallpox (vaccinia) vaccine was administered to federal, state, and local volunteers who might be first responders during a bioterrorism event.


OBJECTIVE
To describe results from the comprehensive DHHS smallpox vaccine safety monitoring and response system.


METHODS
Descriptive study of adverse event reports from the DHHS smallpox vaccine safety monitoring and response system received between January 24 and October 31, 2003, through the Vaccine Adverse Event Reporting System (VAERS) and the Centers for Disease Control and Prevention. A total of 37,901 volunteers in 55 jurisdictions received at least 1 dose of smallpox vaccine.


METHODS
Number of vaccinations administered and description of adverse events and reporting rates.


RESULTS
A total of 38,885 smallpox vaccinations were administered, with a take rate of 92%. VAERS received 822 reports of adverse events following smallpox vaccination (overall reporting rate, 217 per 10,000 vaccinees). A total of 590 adverse events (72%) were reported within 14 days of vaccination. Nonserious adverse events (n = 722) included multiple signs and symptoms of mild and self-limited local reactions. One hundred adverse events (12%) were designated as serious, resulting in 85 hospitalizations, 2 permanent disabilities, 10 life-threatening illnesses, and 3 deaths. Among the serious adverse events, 21 cases were classified as myocarditis and/or pericarditis and 10 as ischemic cardiac events that were not anticipated based on historical data. Two cases of generalized vaccinia and 1 case of postvaccinial encephalitis were detected. No preventable life-threatening adverse reactions, contact transmissions, or adverse reactions that required treatment with vaccinia immune globulin were identified. Serious adverse events were more common among older revaccinees than younger first-time vaccinees.


CONCLUSIONS
Rigorous smallpox vaccine safety screening, educational programs, and older vaccinees may have contributed to low rates of preventable life-threatening adverse reactions. Other rare, clinically significant, or unexpected cardiac adverse events were detected by timely review of VAERS data and intensive clinical case investigation.
Casey
Christine G
CG
Smallpox Vaccine Adverse Event Monitoring and Response Activity, Epidemiology and Surveillance Division, National Immunization Program, Centers for Disease Control and Prevention, Atlanta, Ga 30333, USA. ccasey@cdc.gov
Iskander
John K
JK
Roper
Martha H
MH
Mast
Eric E
EE
Wen
Xiao-Jun
XJ
Török
Thomas J
TJ
Chapman
Louisa E
LE
Swerdlow
David L
DL
Morgan
Juliette
J
Heffelfinger
James D
JD
Vitek
Charles
C
Reef
Susan E
SE
Hasbrouck
La Mar
LM
Damon
Inger
I
Neff
Linda
L
Vellozzi
Claudia
C
McCauley
Mary
M
Strikas
Raymond A
RA
Mootrey
Gina
G
D016907:Adverse Drug Reaction Reporting Systems; D006801:Humans; D011159:Population Surveillance; D012900:Smallpox Vaccine / Q000009:adverse effects*; D014481:United States / Q000453:epidemiology
D012900:Smallpox Vaccine