By Melanie R. Margolis
The possibility that smallpox virus might be used as a weapon of bioterrorism has sparked considerable debate among public health officials and researchers. Smallpox could be a formidable weapon, given that routine smallpox vaccinations were eliminated over a quarter of a century ago. The morbidity and mortality associated with an uncontained smallpox epidemic in a largely unvaccinated population would be quite significant. The threat raises at least two problems: (1) ensuring that the United States and other countries have access to sufficient vaccine supplies; and (2) developing a vaccination strategy that balances the unknown probability of a smallpox outbreak against the known health risks associated with vaccination.
The federal government considers the risk of a smallpox outbreak significant enough to invest in the rapid and dramatic expansion in the supply of smallpox vaccine. In October 2001, the U.S. government contracted for some 209 million doses of smallpox vaccine. These doses are expected to be available at the end of 2002. The CDC National Pharmaceutical Stockpile has developed protocols to allow for the rapid, simultaneous delivery of smallpox vaccine to every state and US territory within 12-24 hours. State and local bioterrorism response plans have been or are being designed to provide for the rapid distribution of vaccine within applicable jurisdictions.
The federal government is also playing a central role in the development of a smallpox vaccination strategy. On June 20, 2002, the Advisory Committee on Immunization Practices (ACIP) issued a Draft Supplemental Recommendation Concerning the Use of Smallpox (Vaccinia) Vaccine. The recommendation, which is now under consideration by the Centers for Disease Control and Prevention (CDC) and the Department of Health and Human Services (HHS), supplements the recommendation issued in June 2001. The supplemental recommendation, available at http://www.cdc.gov/nip/smallpox/supp_recs.htm, addresses vaccination of the general population and of those designated to care for persons with suspected or confirmed cases of smallpox. In addition, the new recommendations clarify the strategy for dealing with a smallpox outbreak.
Surveillance and containment are key components of the primary strategy for controlling an outbreak of smallpox. This strategy consists of identifying infected persons through intensive surveillance, isolating infected persons, vaccinating close contacts of infected persons, and vaccinating household contacts of those close contacts.
Absent any confirmed cases of smallpox , the ACIP recommends not vaccinating the general population at this time because of the significant morbidity and mortality risk associated with the smallpox vaccine itself. The ACIP does recommend vaccinating the following selected groups in order to enhance smallpox response readiness:
state bioterrorism response plans should designate initial smallpox isolation and care facilities, and these facilities should designate in advance individuals who would care for the initial smallpox cases.
The recommendations note the importance of adequate surveillance and diagnostic systems. The risk of smallpox transmission is greatest among people in close contact. Cases of rash illnesses accompanied by fever should be immediately reported to local and/or state health departments. If smallpox laboratory diagnostics are necessary, the CDC Rash Illness Evaluation Team should be consulted. Additional information regarding surveillance activities following laboratory confirmation of a smallpox outbreak can be found in the CDC Interim Smallpox Response Plans and Guidelines.
The new recommendations were developed based on certain factors and assumptions:
These experts compared the ACIP approach with other, more aggressive vaccination strategies. . Their results suggest that mass vaccination after an attack led to many fewer deaths than tracing contacts and vaccinating them. These researchers argue that switching to mass vaccination after first trying tracing vaccination as is contemplated by the interim policy would cause many more deaths and a great loss of time, especially in the face of what would surely be high public demand for vaccinations if an attack occurred. These experts reason that because no accurate screening test exists for smallpox, ACIP should reconsider proceeding straight to mass vaccination in the event of an attack on a large urban center (absent mass pre-attack vaccination).
The CDC and HHS currently are reviewing the ACIP recommendations. Comments will be accepted on-line until July 31, 2002. http://www.cdc.gov/nip/smallpox/supp_recs.htm.