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Small pox and smallpox vaccine

The use of anthrax as a bioterrorism agent has stimulated concern and discussion  regarding the use of smallpox vaccine for healthcare providers, public health officials responsible for investigating potential outbreaks and the general public. In the April 25, 2002 edition of the New England Journal of Medicine, several articles provide valuable information and opinions regarding this issue. New information regarding the clinical responses to smallpox vaccine is provided in 2 articles by Frey and colleagues [see box for links]. 

Photographs of adverse effects and tables of side effects associated with smallpox vaccine in healthy, young adults are provided in Breman and Henderson's article. There were also articles by William Bicknell calling for voluntary smallpox vaccination by the general public. Commentary from Drazen and Fauci call for a national debate on this issue.

Most adverse events peek between 7 and 12 days after vaccination; the time when the local lesions are at the peek at the vaccination site. Approximately 20% of vaccine recipients developed moderate or severe muscle aches or fatigue. Pain at the vaccination site is considered to be moderate and approximately one third of the individuals also noted that the adverse events interfered with work or recreational activities.

More severe side effects are reported in other studies going back to the time when small pox vaccine was used routinely in the United States. Encephalitis developed in 1-5 per thousand individuals vaccinated. When vaccine was inadvertently administered to immunocompromised individuals who did not have adequate cellular immunity, progressive lesions developed that could be fatal unless the limb was amputated. Also, 36.5% reported that they missed work, school or recreational activities because of side effects associated with the vaccine. 

The local infection at the vaccination site can be transmitted to other place on the body by scratching or to immediate direct contacts of people who have received the vaccine. Children or adults who have eczema can develop multiple severe lesions throughout areas affected by eczema and some of these cases have been fatal. If routine vaccination were performed with a catch-up program for all of the people in the United States, experts have estimated that there would be 100-200 deaths from complications from the vaccine.

The Advisory Committee on Immunization Practices (ACIP), which makes recommendations for guidelines for the Centers for Disease Control and Prevention, is currently debating what the specific recommendations should be for smallpox vaccination. Draft guidelines have been developed and will be presented at the June 2002 meeting.

Vaccines currently in use are very safe with only a few moderate-serious side effects. Smallpox vaccine causes more moderate-severe side effects than any vaccine in use today. That is the reason that it was stopped in 1972 after the risk of smallpox in the world had declined considerably (even though this was 5 years prior to the eradication of wild type virus from sources of natural transmission). 

If we were to embark on large-scale immunization of people in this country, there is no question that there would be many serious side effects and the public’s tolerance for such serious side effects has decreased appropriately in recent years due to a lack of known risk of exposure to this disease. There are some in the US military and in high levels of the current government who are actively pursuing a policy allowing everyone who wants the vaccine to receive it. The Institute for Vaccine Safety does not agree with this proposed strategy.

The actual risk of the use of smallpox as a bioterrorism agent is unknown although not zero. Active proponents of bioterrorism would succeed in causing disruption and distrust of government and other public health organizations if we caused far more harm from the routine use of this vaccine than might occur from potential use of smallpox as a bioterrorism agent.

An alternative strategy has been proposed by the CDC. Smallpox vaccine is effective for preventing serious disease when used up to four days after exposure. If there were a recognized release of smallpox then exposed individuals could be vaccinated up to several days after exposure. It is virtually impossible to know when and where a bioterrorist might possibly release smallpox. Undoubtedly, health care workers anywhere in the country could be asked to see patient with possible smallpox. These workers need to be adequately informed that the vaccine does work post-exposure and that the CDC would release the vaccine for them and their colleagues. We believe that this is the most sound strategy at this time and will cause the least harm. CDC may choose to immunize additional ‘first responders’ and some large institutions that care for complicated disorders may choose to immunize a small number of people who would be potentially involved in the care of these patients. These measures may be appropriate but we do not believe that it is indicated for the general public to receive smallpox vaccine and we believe that the recommendation should be against routine vaccination as the risks outweigh the benefits.


This page was last updated on June 09, 2016

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