Laboratory Studies

The diagnosis of vaccinia virus complications is usually straightforward and depends on obtaining the history of recent vaccinia virus exposure by vaccination or contact with a vaccinated individual. A careful workup for immune deficiency should be considered in patients who do not promptly improve.

The diagnosis of CNS complications is more difficult because the signs and symptoms are nonspecific. Although rare, postvaccinial encephalitis should be considered in any patient with neurologic symptoms developing 1-2 weeks after exposure to live vaccinia virus. Vaccinia virus has not been isolated from cerebrospinal fluid (CSF) of patients with encephalitis, and CSF analysis usually produces normal results, except for increased pressure; however, CSF analysis may be indicated to exclude other causes of encephalitis.

Imaging Studies

Imaging studies are not useful in the diagnosis of vaccinia infection or a postvaccinial complication, although imaging modalities may be helpful to exclude other causes of disease (eg, MRI of the brain in cases of suspected encephalitis).

Other Tests

Patients who present with skin manifestations usually have live viral particles replicating in the dermal lesions. The presence of vaccinia virus can be confirmed by obtaining a biopsy of the skin lesion and examination through microscopy, plaque titer assay, Western blot, and polymerase chain reaction (PCR) analysis.

Histologic Findings

Light microscopy may reveal characteristic inclusions (ie, Guarnieri bodies) in the cytoplasm of infected cells. This is distinct from the appearance of cells infected by viruses such as herpes simplex virus, which typically demonstrate intranuclear inclusion bodies.

Treatment & Management

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This typical pustular lesion following vaccinia immunization usually appears within 5 days of vaccination and forms a scab by 10-14 days. Vaccination usually leaves a permanent indentation.

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Table 1. Frequency of Complications Related to Vaccination

Table 1. Frequency of Complications Related to Vaccination

Complication	Number of cases from 450,293 vaccinations administered between 12/13/2002 and 5/28/2003	Department of Defense rate per million vaccinees (95% confidence interval)	Historical number of cases from 1950s and 1960s
Death	0	0 (0-3.7)	Age 1 y at first vaccination - 5 per 1 million primary vaccinees
			Age 1-4 y at first vaccination - 0.5 per 1 million primary vaccinees
			Age 5-19 y at first vaccination - 0.5 per 1 million primary vaccinees
			Age ≥ 20 y at first vaccination - No data
Encephalitis	1	2.2 (0.6-7.2)	3 per 1 million primary vaccinees
Vaccinia necrosum/progressive vaccinia	0	0 (0-3.7)	Approximately 1 patient per million during primary or revaccination
Vaccinia necrosum/progressive vaccinia	0	0 (0-3.7)	Usually fatal over a period of several months
Eczema vaccinatum	0	0 (0-3.7)	1 per 100,000 primary vaccinees
Eczema vaccinatum	0	0 (0-3.7)	1 per 1 million revaccinees
Generalized vaccinia	36	80 (63-100)	Occasional occurrence in immunocompetent individuals
			3 per 100,000 primary vaccinees
			1 per 1 million revaccinees
Accidental vaccinia	48	107 (88-129)	3 per 100,000 to 1 million vaccinees
Erythematous rash	36	80 (63-100)	Approximately 1 per 100,000 primary vaccinees*
Acute myopericarditis	37	82 (65-102)	100 per 1 million vaccinees
*Incidence was slightly higher when vaccination occurred before age 1 year.

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Author

Nikesh A Patel Medical University of South Carolina College of Medicine

Nikesh A Patel is a member of the following medical societies: American Medical Association, South Carolina Medical Association

Disclosure: Nothing to disclose.

Coauthor(s)

Dayna Diven, MD Professor, Department of Dermatology, University of Texas Southwestern Austin Programs

Dayna Diven, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, Idaho Medical Association, Phi Beta Kappa

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Richard B Brown, MD, FACP Chief, Division of Infectious Diseases, Baystate Medical Center; Professor, Department of Internal Medicine, Tufts University School of Medicine

Richard B Brown, MD, FACP is a member of the following medical societies: Alpha Omega Alpha, American College of Chest Physicians, American College of Physicians, American Medical Association, American Society for Microbiology, Infectious Diseases Society of America, Massachusetts Medical Society

Disclosure: Nothing to disclose.

Chief Editor

John L Brusch, MD, FACP Corresponding Faculty Member, Harvard Medical School

John L Brusch, MD, FACP is a member of the following medical societies: American College of Physicians, Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Additional Contributors

Brenda Jones, MD Associate Professor of Clinical Medicine, Division of Infectious Diseases, Keck School of Medicine of the University of Southern California

Disclosure: Nothing to disclose.

Acknowledgements

Ken Flanagan PhD Student, Department of Microbiology and Immunology, Albert Einstein College of Medicine

Ken Flanagan is a member of the following medical societies: American Association for Cancer Research