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POST 00923E : THINKING THE UNTHINKABLE Follow-up on Post 00917E 11 May 2006 ________________________________________________________________ This posting contains two contributions in response to that of Anthony Battersby. The first is from Mogens Munck (mailto:[email protected]) from Spain, and the second from Bob Davis (mailto:[email protected]) from UNICEF/ESARO in Nairobi. NOTE : I wish to draw your attention to an article published in the Archives of Virology last year, "Virus perpetuation in populations : biological variables that determine persistence or eradication" by N. Nathanson, from the University of Pennsylvania. Interesting ideas, and you will also find at pages 7 to 10 a bit of the historical and epidemiological background to the polio eradication initiative. Thanks to Bob Davis and Evelyn Chege for having it circulated earlier through Tech Updates. You can download this article directly from : http://www.technet21.org/pdf_file/PerpetuationVirus.pdf However, I disagree with one of Nathanson’s statement on page 2 : "In the instance of an acute infection, the host acquires lifelong immunity to the infecting virus and is – from an epidemiological perspective – no longer capable of acting as a link in the chain of infection." To my knowledge, there is no disease agent which produces immunity that is instantaneous on any further agression, killing the agent (bacteria or virus) on sight. There is a response delay, varying from disease to disease and host to host, during which a host can possibly act as a link in the chain of transmission. I believe this is precisely the problem with polio. The virus does not cause the disease in an immunized host but it does replicate in the bowels for a length of time depending a number of factors before its effective elimination. This host may not be as effective a transmitter as an acutely infected one, but it does play a role. The virus was carried from Nigeria to Saudi Arabia and then further, not by people with acute disease but likely immunized, whether naturally or vaccinated. This is also a basic principle behind the eradication strategy that calls for vaccinating in a few days, often already immunized children, in order to flood the environment with vaccine viruses. I wish to hear from the real experts on this and also from some members who may know better. Sorry for that longish introduction! _________________________________________________________________ Dear Technet 21, I thank Anthony for his message: "Thinking the unthinkable"! I am not a public health expert, much less an epidemiologist, but a profesional with experience in cold chain and logistics in general, and not least with a lot of interest in immunization. I have always taken care not to speak out on themes outside my expertise, but I would very much appreciate that the issues raised by Anthony be discussed openly. After having done consultancies in Afghanistan and Nigeria I find as a layman that the polio eradication drive with numerous NIDs (often one every second month) does not seem to make sense. The results are hard to see, and worse routine immunization is neglected so heavily that coverage figures for many antigens in many districts are below 50%. Could epidemiologists not explain the polio eradication strategy in a way that would make sense to us laymen? Or admit that the strategy has been a failure? Best regards, Mogens Munck ------------------------------ As in the past, Anthony Battersby's contributions to the Technet are intellectually stimulating. In the following discussion, which reflects only my own views, let me explain why, without disputing Anthony's facts, I draw different conclusions from them. EITHER-OR First, I don't see a zero sum game between eradication initiatives on the one hand and routine EPI on the other. Quite the contrary, the success of polio eradication in clearing most of the planet from a virus which paralyzed >250,000 victims yearly before the '88 WHA resolution, has been a strong advocacy point for EPI as a whole. After a decade of underfunding in the 1990s, it may have influenced new funders, notably the Bill and Melinda Gates Foundation, to lay out new funding, more than $1 billion, for new vaccines and routine EPI. The entire budget envelope for EPI, both routine and eradication, is expanding, aided now by the International Finance Facility for Immunization (IFFIm). IFFIm funds are going both to support of routine EPI and to the strategic stockpile of mOPV needed for the post-eradication period. So the apparent tug-of-war between support for eradication and support for routine is a chimera which dissipates on close examination. Eradication initiatives have, going all the way back to smallpox, lent credibility to vaccination as a whole. Without SEP, there would have been no EPI. Routine vaccination, where properly done (Botswana, Eritrea) prevents reintroduction of diseases targeted for eradication. I see synergies where others see only competition for resources. COST OVERRUNS While the agencies were, in '88, way off in costing the polio eradication initiative, it is still bang for the buck. If we end up spending, by 2010, $4 billion since '88 to prevent about 4 million cases of paralytic polio, then we are paying on the order of $1000 per case of polio prevented, not counting the additional cases prevented in the post-eradication era. Is that too much to pay for prevention of paralysis? This figure of $1000 is less than wealthy persons pay for a face lift in some countries. Polio eradication remains, for all its overruns, one of the most successful and cost-effective public health programmes in history. The point of my much quoted bell curve presentation was that history repeats itself. With both smallpox and polio, funding levels rose during the middle years of the initiative, then declined towards the end, with budget shortfalls as a result. It is a fact of economics that the unit costs of preventing the last few cases of a disease are much higher than those incurred in preventing the first few hundred thousand cases. This is no argument for slowing down as one approaches the finish line; quite the contrary, one should accelerate the pace and finish the job quickly. This prudent course is what my colleague proposes that we not do. Battersby is spot on in saying that polio would not have spread from Nigeria to Indonesia and the Yemen if the latter countries had achieved good routine coverage. The Botswana and Eritrea importations support his analysis: where routine OPV3 coverage exceeds 80 percent, secondary spread from the first importation is rare. However, this is a weak argument against eradication initiatives. Should we wait until all 192 member states have 80 percent coverage before embarking on global eradication initiatives? Had we done so with smallpox, that virus would still be with us. CONTINUING VACCINE PRODUCTION/INTENTIONAL RELEASE OF VIRUSES Yes, there is continuing production of smallpox vaccine for the military, but this comes from defense budgets, not health budgets. So it does not represent a diversion of resources within the health sector. Only Dr Strangelove would consider a biological warfare agent which produces no symptoms in over 99 percent of all infections. Nonetheless, many industrialized countries will, in an abundance of caution, consider continuing use of IPV after eradication to eliminate that remote risk. If developing countries feel themselves vulnerable to intentional release of polio, then stockpiles of vaccine, rather than posteradication vaccination, are likely to be the most logical answer. The argument against eradication based on possible biological warfare is a weak one. BELL CURVES The bell curves of international funding which I presented in an earlier posting were based on the funding data available at that time. I should be delighted to see measles becoming the exception to the bell curve. When the fresh IFFIm measles SIA funding through GAVI begins to flow next year, we shall see a second hump on the curve for measles funding (the first was last year's tsunami funding). What will happen to the Measles Partnership after 2009? A good question. Either the global community will close down the MP -- a disastrous scenario, in my opinion -- or it will move towards eradication with more speed and unity than we have seen in previous initiatives. This would be in line with the measles elimination initiatives launched by the regional governing bodies of WHO member states in four out of six regions. Have 135 member states that already voted for measles elimination failed to do their homework? I don't think so. I hope they will soon be joined by the member states of AFR and SEAR, so that 135 countries are not left in the position of the little Dutch boy holding his thumb in the dike. GIVS The Global Immunization Vision and Strategy, which forms the basis for W.H.O./UNICEF collaboration over the next 10 years, rightly places the main emphasis on routine EPI, new vaccine introduction, and child mortality reduction. None of these things would have been likely, nor would IFFIm funding for EPI have been possible, if the international community had flinched in its commitments to polio eradication, which it has not. To say, at this late stage, that we should slow down before reaching the finish line, would be to snatch defeat from the jaws of victory. Best regards, Bob Davis EPI Regional Adviser, UNICEF/ESARO Nairobi, Kenya ______________________________________________________________________________ Visit the TECHNET21 Website at http://www.technet21.org You will find instructions to subscribe, a direct access to archives, links to reference documents and other features. ______________________________________________________________________________ To UNSUBSCRIBE, send a message to : mailto:[email protected] Leave the subject area BLANK In the message body, write unsubscribe TECHNET21E ______________________________________________________________________________ The World Health Organization and UNICEF support TechNet21. The TechNet21 e-Forum is a communication/information tool for generation of ideas on how to improve immunization services. It is moderated by Claude Letarte and is hosted in cooperation with the Centre de coopération internationale en santé et développement, Québec, Canada (http://www.ccisd.org) ______________________________________________________________________________
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