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Is Mass Smallpox Vaccination The Best Choice?
(commentaries in the New England Journal of Medicine)
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Here are two thought provoking reviews in the next upcoming edition of the New England Journal of Medicine that do not support mass vaccination for the public at this time prior to a terrorist attack of smallpox. The articles present interesting alternative views and strategies of addressing the risk of a smallpox attack by terrorists from a public policy perspective and regarding individual considerations in deciding whether to be vaccinated. One review written by Sam Bozzette and called "A Model for a Smallpox-Vaccination Policy" suggests only health care workers and first line responders get vaccinated prior to an attack. He does not endorse public vaccination at this time. But he supports allowing access to vaccination on demand. The second review called "A Different View of Smallpox and Vaccination". It is written by Thomas Mack and he supports vaccination programs after an attack. Below you will find summaries and excerpts from these two articles, and pdfs of the full text for each article can be downloaded. Both articles suggest individuals should carefully consider the potential benefits and risks for themselves of getting vaccinated for smallpox.
"A Model for a Smallpox-Vaccination Policy"
Samuel A. Bozzette, M.D., Ph.D.
New England Journal of Medicine; 348;5. January 30, 2003
ABSTRACT. Background: The new reality of biologic terrorism and warfare has ignited a debate about whether to reintroduce smallpox vaccination. Methods: We developed scenarios of smallpox attacks and built a stochastic model of outcomes under various control policies. We conducted a systematic literature review and estimated model parameters on the basis of European and North American outbreaks since World War II. We assessed the trade-offs between vaccine-related harms and benefits. Results: Nations or terrorists possessing a smallpox weapon could feasibly mount attacks that vary with respect to tactical complexity and target size, and patterns of spread can be expected to vary according to whether index patients are hospitalized early. For acceptable results, vaccination of contacts must be accompanied by effective isolation.
Vaccination of contacts plus isolation is expected to result in 7 deaths (from vaccine or smallpox) in a scenario involving the release of variola virus from a laboratory, 19 deaths in a human-vector scenario, 300 deaths in a building-attack scenario, 2735 deaths in a scenario involving a low-impact airport attack, and 54,728 deaths in a scenario involving a high-impact airport attack. Immediate vaccination of the public in an attacked region would provide little additional benefit. Prior vaccination of health care workers, who would be disproportionately affected, would save lives in large local or national attacks but would cause 25 deaths nationally. Prior vaccination of health care workers and the public would save lives in a national attack but would cause 482 deaths nationally. The expected net benefits of vaccination depend on the assessed probability of an attack. Prior vaccination of health care workers would be expected to save lives if the probability of a building attack exceeded 0.22 or if the probability of a high-impact airport attack exceeded 0.002. The probability would have to be much higher to make vaccination of the public life-saving. Conclusions: The analysis favors prior vaccination of health care workers unless the likelihood of any attack is very low, but it favors vaccination of the public only if the likelihood of a national attack or of multiple attacks is high. Notice: To help to inform the current national debate about smallpox vaccination, this article has been published early (on December 19, 2002). The article will
appear in the January 30, 2003, issue of the Journal.
EXCERPTS. Our model suggests that prior vaccination of health care workers can be expected to save lives unless the risk of an attack is low. Encouraging vaccination of the public can be expected to save lives in coordinated multisite attacks but will cause substantial harm under most other circumstances.
In our judgment,the probability of a release of variola virus may exceed the thresholds for prior vaccination of health care workers. We endorse a policy of vaccinating all eligible health care workers and first responders before an attack.Local officials should welcome such a program, which should include appropriate monitoring and evaluation.In contrast,we cannot endorse a public vaccination campaign at this time,because the certainty of harm outweighs the small chance of a net benefit. Nonetheless,we acknowledge the distinction between this position and the argument for allowing access to vaccination on demand.
...controlling past outbreaks. A model of a community of 2000 indicates that mass vaccination is more effective but less efficient than targeted vaccination
and that increasing preexisting immunity with prior vaccination closes the efficacy gap. However, neither model explicitly considers policymaking at
a scale at which many deaths from vaccination are expected...
"A Different View of Smallpox and Vaccination"
Thomas Mack, M.D., M.P.H.
New England Journal of Medicine; 348;5. January 30, 2003
Costs and Benefits
Extrapolating from the European experience, we can predict that an initial smallpox introduction is likely to result in substantially fewer than 20 cases and 10 deaths; experience would lessen the impact of subsequent introductions. Many wellinformed members of the general public will refuse vaccination. Every million primary vaccinations will cause at least 3 deaths from vaccinia, and the chance of preventing deaths from smallpox would be less than 0.4 percent (1 in 275 million).To prevent all potential deaths from smallpox would require universal compliance with vaccination,with as many as 800 deaths from complications. Even after an introduction, mass vaccination would do more harm than good.
About 2 1/2 million health care professionals and technicians work in U.S. hospitals and are at some excess risk of caring for a patient with smallpox. Vaccination of the entire 2 1/2 million, assuming 100 percent compliance, would prevent all deaths of caregivers from smallpox, but at a cost of at least 7 to 8 deaths from vaccinia. Risk to other members of the antiterrorist infrastructure is likely to be similar to that of the general public.
Better Options
A terrorist introduction of smallpox could produce a short outbreak of cases and deaths,but the current vaccination policy will provide little protection,
and the cost in deaths from vaccine complications will outweigh any benefit. Only if evidence suggests that a massive attack or sustained biologic warfare
is probable can such a vaccination policy be justified. Safer options would be more effective.
I recommend the following. Every effort should be made to facilitate rapid
diagnosis. Posters with dramatic photographs of florid smallpox cases should be distributed widely. No suspicious patient should be admitted to or even knowingly examined at a general hospital, even one with isolation facilities and an already vaccinated staff. Alternative dedicated facilities, even National Guard field hospitals, should be identified and activated at first diagnosis. Limited numbers of preselected (preferably older, previously vaccinated) field investigators, diagnostic laboratory personnel, caregivers, and paramedics and some law-enforcement personnel should be recruited, vaccinated, and committed to serve wherever necessary in the event of an introduction. No more than 15,000 persons would be required. Reserves of vaccinia immune
globulin should be large enough to meet the anticipated need for both treatment of complications and postexposure smallpox prophylaxis. Experts
should be convened to develop protocols for post exposure prophylaxis and treatment. Finally, the authorities and the media should provide more de-
tail about the dangers of vaccination and more accurate,less inflammatory information about the potential for the spread of smallpox.
...Nearly twice as effective as vaccine alone, however, is vaccination
followed by the administration of vaccinia immune globulinŠŠVaccination before importation offers the only possible protection to households directly targeted by an introduction (assuming that genetic engineering has not rendered the strain of virus resistant). However, we cannot identify those households in advance,and vaccinia is a dangerous live vaccine. It causes substantial morbidity among both healthy vaccinees and their pregnant or eczematous contacts. Despite recommendations for screening and treatment with vaccinia immune globulin, deaths from complications occurred at a rate of 1 to 2 per million primary vaccinees. Today,immunosuppressed patients with chronic disease or transplanted organs and carriers of the human immunodeficiency virus with or without AIDS, especially those with skin lesions, constitute additional vulnerable groups. Complications today will surely be several times as common as previously. Even with a rate of 3 deaths per million, primary vaccination of 250,000 persons would be more likely than
not to cause death. Moreover, liability for complications is unclear, marketing prophylaxis to adults is generally unsuccessful ,and herd immunity will be difficult to achieve.Vaccine complications will be quickly, widely, and graphically reported in the media. Americans are better informed and less
trusting than in the past, and noncompliance will be common.
Caregivers, at high risk of secondary transmission, deserve preferential protection. However,we cannot predict which hospitals will be affected, and
undertaking staff vaccination through programs at all hospitals poses serious problems. There is substantial turnover among emergency room personnel, and some caregivers will refuse to be vaccinated. It will be difficult to protect highly vulnerable inpatients and outpatients from the spread of vac-
cinia. Moreover, the existence of hospital-based vaccination programs may lead to the knowing admission of patients with smallpox, putting those
who are not protected at very high risk...
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