Smallpox Vaccination of Laboratory Workers at US Variola Testing Sites

Sharon Medcalf

, Laura Bilek, Teresa Hartman, Peter C. Iwen, Patricia Leuschen, Hannah Miller, Anne O’Keefe, Harlan Sayles, and Philip W. Smith

Author affiliations: University of Nebraska Medical Center, Omaha, Nebraska, USA

Abstract

To evaluate the need to revaccinate laboratory workers against smallpox, we assessed regular revaccination at the US Laboratory Response Network’s variola testing sites by examining barriers to revaccination and the potential for persistence of immunity. Our data do not provide evidence to suggest prolonging the recommended interval for revaccination.

The eradication of smallpox (variola) is arguably the greatest public health feat in the history of civilization. Smallpox was an infectious disease that plagued global health from the earliest documented settlements (1500bce) through nearly the end of the 20th century (1). In 1980, the World Health Organization declared that smallpox was eradicated and paid homage to a large cadre of dedicated and tireless persons who collectively eliminated a disease that had killed one third of its victims for >3,500 years (2).

Despite concern about the existence of live smallpox virus housed in government research laboratories in the United States and the Soviet Union (later Russia), not until 2002 did the US government declare the resurgence of smallpox a credible biothreat (1). In the United States, the Department of Health and Human Services launched a national campaign to vaccinate volunteers from health care and public health professions. The 2003 National Smallpox Vaccination Program resulted in the vaccination of almost 40,000 volunteers in 9 months in the United States (2).

After the National Smallpox Vaccination Program ended in October 2003, experts at the Centers for Disease Control and Prevention (CDC; Atlanta, GA, USA) and members of the Advisory Committee on Immunization Practices (ACIP) met to determine future steps for response planning. These experts recommended that vaccinated persons from health care and public health professions be revaccinated only if a smallpox event occurred. However, laboratory workers handling orthopoxviruses at the proposed variola testing sites would need to be revaccinated every 3 years to maintain optimal immunity or protection. The ACIP admitted that this recommendation was based on “best available science, historic precedent, and expert opinion” (3). Although the ACIP recommendations do not address the frequency with which workers are exposed to orthopoxviruses, they imply that even periodic exposure to these viruses might warrant the protection that only vaccination can provide. Some orthopoxviruses remain extremely dangerous (high rates of illness and death) for humans (4).

During 2012, we further evaluated the need for revaccination of laboratory workers by examining barriers to revaccination and the potential for persistence of immunity in laboratory workers at the Laboratory Response Network (LRN) variola testing sites who had received at least 1 smallpox vaccination since 2003. Our intent was to balance the risks for rare exposures to the virus against the risks for severe adverse events from the vaccine.

Dr. Medcalf is an assistant professor in the College of Public Health, University of Nebraska Medical Center; co-director of the Center for Biosecurity, Biopreparedness and Emerging Infectious Diseases; and program director for the Master of Science program in Emergency Preparedness at the University of Nebraska Medical Center’s College of Public Health. Her research interests include health care preparedness, smallpox vaccination, pandemic influenza, and women in disasters.

Acknowledgment

We thank Jasmine Chaitram for her assistance as liaison between the surveyors and the laboratory workers at national variola testing sites.

References

Berche P. The threat of smallpox and bioterrorism. Trends Microbiol. 2001;9:15–8 . DOI PubMed
Baciu A. The smallpox vaccination program: public health in an age of terrorism. Washington (DC): National Academies Press; 2005.
Barnett DJ, Balicer RD, Thompson CB, Storey JD, Omer SB, Semon NL, Assessment of local public health workers’ willingness to respond to pandemic influenza through application of the Extended Parallel Process Model. PLoS ONE. 2009;4:e6365 . DOI PubMed
Wu JJ. Vaccines and immunotherapies for the prevention of infectious diseases having cutaneous manifestations. J Am Acad Dermatol.2004;50:495–528. DOI PubMed
Centers for Disease Control and Prevention. CDC interim guidance for revaccination of eligible persons who participated in the US Civilian Smallpox Preparedness and Response Program. October 2008 [cited 2014 May 1]. http://www.bt.cdc.gov/agent/smallpox/revaxmemo.asp
Mortimer PP. Can postexposure vaccination against smallpox succeed? Clin Infect Dis. 2003;36:622–9. DOI PubMed
Gordon SN, Cecchinato V, Andresen V, Heraud JM, Hryniewicz A, Parks RW, Smallpox vaccine safety is dependent on T cells and not B cells. J Infect Dis. 2011;203:1043–53. DOI PubMed
Benzekri N, Goldman E, Lewis F, Johnson CC, Reynolds SM, Reynolds MG, Laboratory worker knowledge, attitudes and practices towards smallpox vaccine. Occup Med (Lond). 2010;60:75–7. DOI PubMed
Artenstein AW. New generation smallpox vaccines: a review of preclinical and clinical data. Rev Med Virol. 2008;18:217–31. DOI PubMed
Alcami A, Damon I, Evans D, Huggins JW, Hughes C, Jahrling PB, Scientific review of variola virus research, 1999–2010. Report no. WHO/HSE/GAR/BDP/2010.3. Geneva: World Health Organization; 2010.
Coulibaly S, Brühl P, Mayrhofer J, Schmid K, Gerencer M, Falkner F. The nonreplicating smallpox candidate vaccines defective vaccinia Lister (dVV-L) and modified vaccinia Ankara (MVA) elicit robust long-term protection. Virology. 2005;341:91–101. DOI PubMed
Henderson DA. Smallpox epidemic models and response strategies. Biosecur Bioterror. 2013;11:73–4. DOI PubMed
Fracasso LA. Developing immunity: the challenges in mandating vaccinations in the wake of a biological terrorist attack. DePaul J Health Care Law.2010;13:1.

Suggested citation for this article: Medcalf S, Bilek L, Hartman T, Iwen PC, Leuschen P, Miller H, et al. Smallpox vaccination of laboratory workers at US variola testing sites. Emerg Infect Dis. 2015 Aug [date cited]. http://dx.doi.org/10.3201/eid2108.140956

DOI: 10.3201/eid2108.140956