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Rapid Responses: Rapid Responses published:
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Global public health infrastructure to respond to outbreaks, including smallpox
- Cathy E. Roth, Pat Drury, Roberta Andraghetti, Ray R. Arthur, Michael J. Ryan, Guenael Rodier, David L. Heymann (19 December 2002)
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Smallpox Bioterror Response
- Edward H Kaplan, Lawrence M. Wein (25 December 2002)
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Smallpox mass vaccination
- Selwyn St Leger (10 January 2003)
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1978 Accidental Birmingham laboratory Release of smallpox virus - Are lessons learnt relevant today?
- Surinder S Bakhshi (30 January 2003)
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Cathy E. Roth, Medical Officer, Department of Communicable Disease Surveillance and Response/CDS World Health Organization, 20 Av. Appia, 1211 Geneva, Switzerland, Pat Drury, Roberta Andraghetti, Ray R. Arthur, Michael J. Ryan, Guenael Rodier, David L. Heymann
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Editor, The editorial describing the interim smallpox guidelines for the U.K. (BMJ 2002;325:1371-2) raises the question of how countries lacking the public health infrastructure to respond to outbreaks, and without their own vaccine supplies, would be able to control an outbreak of smallpox. The World Health Organization(WHO)is able to assist countries to respond to the threat of smallpox through a program of activities including outbreak intelligence and verification, support for outbreak response, the maintenance of an emergency vaccine reserve, and public health information and guidance. Confronted with the threat of intentional release of biological agents, WHO Member States acknowledge the importance of public health operations and infrastructure at all levels for early detection and immediate response. WHO’s approach has been to advocate an astute "dual use" investment that prepares for this potential threat to global health security while also providing a clear and sustainable public health benefit. In May 2002, the World Health Assembly, representing the 192 Member States of WHO, adopted a resolution urging all the Member States to share expertise, supplies and resources to contain such a global health threat, and requesting WHO to develop collective mechanisms to contain or mitigate the impact which the release of such an agent would produce (WHA55.16, 18 May 2002).(1) WHO already manages a stockpile of vaccine against smallpox for emergency use.(2) This stockpile was created after the successful eradication program, which terminated in 1979. WHO activities to identify an adequate global reserve, in line with current concerns, have included engaging with the Ministers of Health of the G7+ Mexico in the Global Health Security Initiative. The Health Ministers of the G7+Mexico countries, in their Third Ministerial Meeting in Mexico City in early December, undertook… “to support and increase the existing WHO global vaccine reserve for emergency response to outbreaks of smallpox that might occur anywhere in the world… and encourage others to do the same.” The Global Smallpox Vaccine Reserve and mechanism for rapid distribution is only one element of smallpox preparedness with which WHO can assist countries. WHO has been working intensively to support Member States with state-of-the-art technical guidance, real-time information, and assistance with building national preparedness for epidemics of either natural or intentional origin. WHO’s Global Alert and Response activities would be vital to effective international containment efforts. WHO’s Global Alert and Response program detects rumours of outbreaks and, in close collaboration with ministries of health in affected countries, verifies or refutes such rumours, and rapidly offers countries technical and operational support for outbreak response through WHO and the Global Outbreak Alert and Response Network, a collaboration of 110 public health institutions and networks worldwide.(3) In the past 2 years, WHO has detected, investigated, and refuted 8 smallpox rumours. Other support to country preparedness for a smallpox outbreak is being provided in the form of training, in collaboration with the US Centers for Disease Control and Prevention and others, for laboratorians, clinicians, and epidemiologists for outbreak response, as well as provision of health information and guidance. Guidance on immunisation strategies, clinical and laboratory diagnosis, and biosafety issues is available from WHO, and a wide range of public health information materials on smallpox for healthcare professionals and the general public are available on the WHO website at: http://www.who.int/emc/diseases/smallpox/ and: http://www.who.int/emc/diseases/smallpox/factsheet.html C.E. Roth, P. Drury, R. Andraghetti, R.R. Arthur, M. Ryan, G. Rodier, D.L. Heymann 1 Public health response to natural occurrence, accidental release or deliberate use of biological and chemical agents or radionuclear material that affect health. World Health Assembly resolution WHA 55.16, 2002. Available electronically at: http://www.who.int/gb/EB_WHA/PDF/WHA55/ewha5516.pdf 2 The global eradication of smallpox: Final report of the Global Commission for the Certification of Smallpox Eradication. Geneva, World Health Organization 1980. Available electronically at: http://whqlibdoc.who.int/publications/a41438.pdf 3 Heymann DL, Rodier GR. Hot spots in a wired world. Lancet Infect Dis 2001: 1: 345–353. Competing interests: None declared |
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Edward H Kaplan, Beach Professor of Management Sciences and Public Health Yale School of Management, 135 Prospect Street, New Haven, CT 06511-3729, USA, Lawrence M. Wein
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Harling et al1 report that the recent smallpox models of Halloran et al2 and Kaplan et al3 reach different conclusions regarding the ability of mass versus targeted vaccination (or ?search and containment?) to control a smallpox outbreak, that this is due to a difference in population mixing assumptions, and that Britain has adopted the latter strategy. However, a close read of Halloran et al2 reveals that unless one believes that a substantial fraction of the population remains protected from vaccinations received 20+ years ago, post-attack mass vaccination prevents more smallpox deaths than an approach based on case-tracing in their model as well. While it is true that Halloran et al2 report that their ?structured simulator? does not produce the ?two orders of magnitude difference? between the number of deaths under targeted versus mass vaccination that we obtained in modeling emergency response to a smallpox attack, the real explanation for this is not due to the differences in mixing patterns as both Halloran et al2 and Harling et al1 claim. Rather, the results differ due to the different scenarios considered: 1-5 initial infections in a community of 2,000 in Halloran et al2 versus 1,000 initial infections in a city of 10 million in Kaplan et al3. To see that this is indeed the case, below we compare the number of deaths per thousand that result from the model of Halloran et al2 as reported in the first column of their Table 2 to the number of deaths per thousand that result from the Kaplan et al3 model for the same model inputs: a population of 2,000, a single initial infection, a reproductive number (secondary infections per initial infection) of Ro = 3.2, 80% vaccination coverage, and response delays of 7, 27 and 37 days to match the detection of smallpox after the 1st, 15th, and 25th case (MV = mass vaccination; TV = targeted vaccination). Deaths per 1000 Halloran et al2 Kaplan et al3 80% MV after: 1 case 0.9 0.4 15th case 9.4 6.4 25th case 13.7 17.8 80% TV after: 1 case 10.9 8.8 15th case 19.6 12.0 25th case 28.2 33.9 Once the models are compared on the same scale, the results are very similar. Since newly identified cases are required to trigger contact tracing, TV proceeds with the pace of the epidemic, and the number of deaths scales with the population size, independently of the number of initial infections. By contrast, MV operates on a timetable dictated by available vaccination resources ? 10 days in the examples above ? and thus the number of deaths, while dependent on how many are infected initially, is largely independent of the population size. As argued in both Halloran et al2 and Kaplan et al3, the models suggest that targeted vaccination would work best in an already immunized population. However, it is not prudent to enact a policy that depends upon such an assumption in responding to a smallpox bioterror attack. Indeed, as an empirical matter, it is not at all clear that even in situations where a substantial fraction of the population was already immunized, targeted vaccination prevented more cases than would have been expected from increased vaccination coverage alone, as recently shown in Kaplan and Wein4. That policy makers such as Harling et al1 have turned to models for additional guidance as they seek to design bioterror response policies is commendable, but failing to understand the models reviewed is both counterproductive and dangerous. The single most important factor in the control of smallpox or any other contagious disease is the level of population immunity against the infectious agent. Post-attack mass vaccination provides the most efficient method for rapidly increasing such immunity in the unlikely event of a smallpox bioterror attack. Edward H. Kaplan, PhD Yale School of Management and Yale School of Medicine Yale University Lawrence M. Wein, PhD Graduate School of Business Stanford University 1. Harling R, Morgan D, Edmunds WJ, Campbell H. Interim smallpox guidelines for the United Kingdom. BMJ 2002;325:1371-2. 2. Halloran ME, Longini IM, Nizam A, Yang Y. Containing bioterrorist smallpox. Science 2002;298:1428-32. 3. Kaplan EH, Craft DL, Wein LM. Emergency response to a smallpox attack: the case for mass vaccination. Proc. Natl. Acad. Sci. U.S.A.2002;99:10935-40. 4. Kaplan EH, Wein LM. Smallpox eradication in West and Central Africa: surveillance-containment or herd immunity? Epidemiology 2002;14:90-92. Competing interests: We are the co-authors of one of the articles cited by Harling et al |
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Selwyn St Leger, Senior Lecturer in Public Health Medicine University of Manchester, Manchester, UK, M13 9PL
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News reports indicate that the UK government has amassed 60 million doses of smallpox vaccine: sufficient for the entire population. Would it not be sensible to start a voluntary mass immunisation programme targetted at those who don't have recognised contra-indications to smallpox vaccination? The known risks to the eligible population could be expressed in simple language and disseminated so that people may make up their own minds. An advantage of this move, assuming uptake is high, would be raising the proportion of immune individuals above the threshold level at which the probability of a sustained outbreak becomes low. Thus, individuals for whom vaccination is inadvisable would be protecteted too. I don't understand why the policy and debate centres on firefighting measures (as in the foot and mouth epidemic) when these would presumably offer the least protection to that vulnerable section of the population that should not be immunised. Also, the storage life of the vaccine would be an issue. It would be a shame not to use it given the investment. The logistics of mass vaccination are always problematic. However, as no evidence has been given of immediate threat, vaccination could be done over two or three years with the firefighting approach in reserve in case an attack occurs sooner. Competing interests: None declared |
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Surinder S Bakhshi, Retired Consultant in Communiacble Disease Ccontrol 48 vernon Avenue, B20 1DF (home address)
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Department of Health interim guidelines for management of deliberate release of smallpox virus are deeply flawed (www.doh.gov.uk/smallpoxguidelines)1. The guidelines assume a one- dimensional picture of a clinical emergency. It will prove to be anything but. Governmental control of a national emergency is legitimate. The Department of Health, however, is not set up to deal with a civil emergency, as severe disruption of the community life, panic, likely violation of human rights and the sheer logistics of managing even a single smallpox case makes it an issue of civil defence to be managed at the highest possible government level Besides riding roughshod over local government’s legal authority to manage a notifiable disease bypasses tried operational procedures entrenched in the community using local resources. Meltdown of the proposed arrangements will be inevitable at the mere whisper of an occurrence of an incident. Little consideration is given too to personal freedom issues except to note that unimmunised patients will be soon too ill to resist compliance. They may of course spread the infection freely until they become moribund. The accidental Birmingham laboratory release of small poxvirus in August 1978 during the countdown of world smallpox eradication resulted in the population of a major urban city systematically searched for first line contacts and isolated from the rest of the community for the first time in modern public health history. A massive surveillance-containment organisation was set up to offer social, clinical, diagnostic and pathological support to the population at risk and rest of the community for unexplained fevers especially those accompanying a rash. 2. Considering an annual Birmingham birth rate of over 15,000 babies (a child population of 75,000 under 5 years of age), the number of daily cases of chicken pox in the city alone required roving medical teams, working round the clock, to deal with chickenpox reported in their hundreds weekly. 60 doctors, 40 nurses, 85 environmental health officers, 6 disinfecting operators and 90 administrative, clerical and support staff took part in the control - operated twenty-four hours a day - for 6 weeks and then for another six weeks of winding down of the outbreak management. 3. The city was divided into four operational units and 30 telephone lines were installed at a time when communication needs were considerably less sophisticated than today. Smallpox vaccination was not an issue as the source of the infection was soon located and shut down. It would have added considerably to the resource requirements if immunisation clinics had to be set up. Besides, the emphasis was on surveillance containment. A policy based on immunisation unaccompanied with vigorous isolation of contacts would probably have resulted in a confused picture of persons at risk mixing freely with the non-contact population. Three hundred and twenty-eight (5000 person-days) of 414 general Categories contacts were placed under quarantine. Of these 75 contacts were considered close category A contacts. Category A contacts were put under medical surveillance, while category B and other contacts were under nursing supervision. And that was for just one smallpox case! This was the nightmare picture in the summer of 1978 in Birmingham. Mitigating circumstances were that most of the adult population was reasonably immune to small pox because of previous vaccination. Further a relatively stable population, familiar with smallpox infection and more compliant in its time than now were other supportive factors. The incident was brought to a conclusion to the satisfaction of WHO without delaying the world smallpox eradication timetable. I predict personal freedom objections from the community and Health care workers against vaccination 4. Not only can smallpox vaccination leaves an ugly scar, it is not clear if the benefits of smallpox vaccination outweigh the risks to vaccinees, their families and patients. We already know of the reluctance of NHS staff to accept influenza vaccination for occupational reasons. There will also be the bar to Department of Health to use public health infection control legislation to ensure compliance as that is the remit of the local authority excluded from control management. Managing deliberate release of smallpox virus is a civil defence matter of the utmost national importance requiring emergency action at the highest government level. Nothing less will do. The confusion in the handling of the anthrax scare is an abject lesson in planning inappropriately at local levels. Deliberate launch of smallpox virus will be an unparalleled escalation of act of bioterrorism. We underestimate its impact at our peril. Yours truly Surinder Bakhshi Consultant in communicable Disease control (Retired) References 1.Interim smallpox guidelines for the United Kingdom Harling R, Morgan D,Edmunds WJ and Campbell H. BMJ 2002; 325: 1371-1372 2.Department of Health. Memorandum of the outbreaks of smallpox. London: DoH 1977 3. Nicol W, Bakhshi SS. Exotic infectious diseases -smallpox. Royal Society of Health Journal April 1980 4 Moynihan R. Health professional challenge US smallpox vaccination plan (News). BMJ 2003: 326, 179. Competing interests: None declared |
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