Safety Profile of Smallpox Vaccine: Insights from the Laboratory Worker Smallpox Vaccination Program
1Immunization Safety Branch, Epidemiology and Surveillance Division, National Immunization Program, 2National Center for Infectious Diseases, and 3Bioterrorism Preparedness and Response Program and 4CDC Drug Service, Scientific Resources Program, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia
Background.
The frequency of mild‐to‐moderate adverse events following smallpox vaccination was not well documented or reported during the pre‐eradication era. This report describes the frequency of such symptoms among 936 adult smallpox vaccinees with and without a history of prior smallpox vaccination.
Methods.Diary cards were distributed to 1006 laboratory workers and members of the Centers for Disease Control and Prevention (CDC) smallpox response team who received smallpox vaccination under an investigational new drug protocol during 2001–2002. Vaccinees were requested to complete the diary card daily and return it to the CDC 28 days after vaccination. The proportion of vaccinees reporting symptoms was determined and compared among subgroups.
Results.Ninety‐three percent of the diary cards were returned. The most common symptom reported was “itching at vaccination site.” Primary vaccines reported statistically higher proportions of the following 11 symptoms: joint pain (25% vs. 11%; 
), muscle pain (46% vs. 19%; 
), fatigue (43% vs. 29%; 
), swelling at vaccination site (58% vs. 33%; 
), itching on the body (31% vs. 17%; 
), abdominal pain (11% vs. 2%; 
), swollen or tender lymph nodes (71% vs. 33%; 
), pain at injection site (48% vs. 30%; 
), headache (40% vs. 25%; 
), backache (17% vs. 7%; 
), and fever (temperature, 
100°F [37.7°C]; 20% vs. 9%; 
).
Conclusions.This analysis suggests that previously unvaccinated persons aged <30 years experienced more symptoms than did previously vaccinated persons. The findings of increased proportions with joint pain, abdominal pain, backache, and difficulty breathing were unexpected. As with recently described cardiac adverse events, these symptoms are suggestive of systemic involvement and warrant further study.
Received 10 August 2004; accepted 3 December 2004; electronically published 16 March 2005.
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