Global eradication of poliomyelitis: benefit-cost...

Global eradication of poliomyelitis:benefit-cost analysisK.J. Bart,1 J. Foulds,2 & P. Patriarca3

A benefit-cost analysis of the Poliomyelitis Eradication Initiative was undertaken to facilitate national andinternational decision-making with regard to financial support. The base case examined the net costs andbenefits during the period 1986-2040; the model assumed differential costs for oral poliovirus vaccine (OPV)and vaccine delivery in industrialized and developing countries, and ignored all benefits aside from reduc-tions in direct costs for treatment and rehabilitation. The model showed that the "break-even" point at whichbenefits exceeded costs was the year 2007, with a saving of US$ 13600 million by the year 2040. Sensitivityanalyses revealed only small differences in the break-even point and in the dollars saved, when comparedwith the base case, even with large variations in the target age group for vaccination, the proportion of case-patients seeking medical attention, and the cost of vaccine delivery. The technical feasibility of globaleradication is supported by the availability of an easily administered, inexpensive vaccine (OPV), theepidemiological characteristics of poliomyelitis, and the successful experience in the Americas with elimina-tion of wild poliovirus infection. This model demonstrates that the Poliomyelitis Eradication Initiative iseconomically justified.

IntroductionDeveloping countries are confronted with destabil-izing health problems and with a serious shortageof resources. The prospects for per capita incomegrowth in many countries have deteriorated, and theadoption of structural adjustment policies calls for arigorous review of public investment programmes.The allocation of resources in the health sector in thepast has not been efficient and equitable, owing toan emphasis on expensive urban and hospital-basedcurative care, and was not directed at the maincauses of ill health in the majority of the population,especially in the less developed countries.

Only in the past decade has immunization, oneof the least expensive and most cost-effective of allhealth interventions, which has been confirmed bycost analyses, been accorded a high priority (1). Theprospect of removing the burden of a disease and itstreatment for ever, and at the same time eliminatingthe continuing costs of vaccinations, is an attrac-tive policy alternative. Prior to the development and

I Associate Director for Medical and Scientific Affairs, Office ofInternational Health, Office of the Secretary, Department of Healthand Human Services (DHHS), Room 18-74, 5600 Fishers Lane,Rockville, MD 20878, USA. Requests for reprints should be sent tothis author.2 Project Officer, Division of Microbiology and Infectious Diseases,National Institute of Allergy and Infectious Diseases, National Insti-tutes of Health, DHHS, Bethesda, MD, USA.3 Associate Director for Medical Affairs, Division of Viral Products,Office of Vaccines, Center for Biologics Evaluation and Research,Food and Drug Administration, DHHS, Bethesda, MD, USA.Reprint No. 5670

introduction of poliomyelitis vaccine, up to 32 outof every 100000 children born in the world hadpermanent lameness as a result of infection withpoliovirus (2-4).

The early successes in the Americas, throughthe expanded programmes on immunization (EPI),led the Forty-first World Health Assembly in May1988 to adopt a resolution (WHA41.28) to eradicatepoliomyelitis from the world by the year 2000 (5).This goal was confirmed in 1990 at the WorldSummit for Children (6). Poliomyelitis eradicationis an example of the EPI focus on the impact ofimmunization on a target disease. In addition, theprogress towards such eradication is seen as pro-viding a measure of the progress towards achievingthe WHO goal of Health for All by the year 2000,i.e., reaching and maintaining >90% coverage withcurrent EPI antigens for all children (7, 8). UnderWHO's global leadership of EPI, an estimated 80%of the world's children were fully immunized in 1993against poliomyelitis; even so, the disease still causesparalysis in over 100000 individuals each year andkills perhaps more than 10000 (9).

The decision to undertake eradication has eco-nomic implications for the poorest countries anddonors who are concerned about the potential todivert resources from other activities with a poten-tially greater impact or to interfere with the develop-ment of primary health care (10-13). A benefit-costanalysis of global poliomyelitis eradication wastherefore recommended so that decisions aboutnational and international financial support for thiseffort could be made.

Bulletin of the World Health Organization, 1996, 74 (1): 35-45 WHO Bulletin OMS. Vol 74 1996 35

K.J. Bart et al.

MethodsThe modelThe global poliomyelitis eradication programme hasbeen modelled as a unit effort from the beginning ofthe first eradication efforts, with projections beyonderadication; benefits have been calculated up to theyear 2040. The number of children to be immunizedwith oral poliomyelitis vaccine (OPV) annually, thedisease incidence and morbidity, and the vaccine'sefficacy permit an estimation of the number of casesprevented by vaccination and the cost of achievingthese reductions. Reductions in the morbidity andmortality, and the consequent drop in demand fortreatment and rehabilitation constitute the principalbenefits of OPV vaccination in the base case (seebelow). In addition, in order to approach a morecomplete estimate of net present value, additionaldirect benefits of eradication, i.e., the savings in vac-cine and its delivery, have been added to the treat-ment and rehabilitation costs and compared with thecost of the programme to determine whether theprogramme is economically justifiable (14-18).ac

The analysis has attempted to maximize thecosts and minimize the benefits in order to constructthe least favourable balance in the benefit-cost rela-tionship of poliomyelitis eradication. Because it isdifficult and often controversial to place dollar val-ues on many of the elements on the benefit side ofthe benefit-cost equation, only the savings in treat-ment and rehabilitation following the reduced inci-dence of disease have been used as the benefits inthis analysis. If eradication can be seen to have afavourable benefit-cost ratio while ignoring all othertangible reductions in the costs to the communityand the family, the long-term handicaps, the value oflife and income calculations as well as intangible andexternal benefits, it would be expected to be evenmore cost-beneficial when these other benefits aretaken into account, no matter how or at what levelthey are valued. In addition, this approach enablescomparison with the analysis that was carried out forthe Americas (19).

For each of the years of the model programme,estimates were made of the number of paralytic po-liomyelitis cases that would be prevented, the costs

a EPI. Poliomyelitis surveys by regions. EPI Information System.Section 3, Table 3.4, July 1988 (unpublished).b World Health Organization. Global poliomyelitis eradication bythe year 2000: plan of action. Revised 1992. Unpublished docu-ment WHO/EPI/Polio/92.2, 1992.c World Health Organization. Progress towards the global eradi-cation of poliomyelitis: status report. March 1994. Unpublisheddocument WHO/GPV/Polio/94.1, 1994.

of treatment and rehabilitation of that number ofpoliomyelitis cases, the cost of the eradication effort(the vaccine, the cold chain, administration of theprogramme, the deployment of delivery teams,social mobilization and the immunization strategychosen), and the net benefit (i.e., the reduced treat-ment and rehabilitation costs). The analysis com-pares the annual total costs with the total benefitsthroughout the entire period from pre-eradicationtill after eradication (20, 21).d

The analysis presented is a model designed tosimulate as closely as possible the global eradicationprogramme now being undertaken. While the modelsimulates what is taking place, some inputs, costs andprogramme projections can only be estimated andmay differ from country to country within regions aswell as between regions. For example, what propor-tion of a childhood population will be reached duringa national vaccination day, "mop-up",e or outbreakresponse; and will there be just 5 years of nationalvaccine days or more than that, 2 years of mop-up,and the undertaking of significant outbreak responseactivities? Estimates of costs and benefits and pro-jections were selected from country experiences.

Sensitivity analyses were performed where dif-fering programme strategies, e.g., age of the targetpopulation for national vaccination days, discountrate and the cost of vaccine, or where costs varywidely in published data between country experi-ences, such as the cost to immunize a child or theamount of vaccine wastage. Only one assumptionis varied at a time in the base case to test the effectof each parameter in question. Since the estimatesof costs are only available from some countries,data reviews and surveys for the less devel-oped countries" and for industrialized coun-triesj were used in addition to individual published

dGarlow DC. Mass vaccination to combat polio: a cost-benefitanalysis for Brazil. Instituto de Pesquisas e Estudos Econimics,Universidade Federal de Rio Grande Do Sul, 1993 (in English,unpublished).e Mop-up efforts are intensive house-to-house vaccinationcampaigns designed to reach and immunize children who are atspecial risk of infection.I World Health Organization. Expanded Programme on Immun-ization: EPI costing guidelines. Unpublished document WHO/EPI/79/5, 1979.9 Brenzel L. The cost of EPI: lessons leamed from cost and cost-effectiveness studies of immunization programs. REACH ProjectPaper, 1990 (unpublished document).h Patriarca P. Cost of delivering OPV in the developing world-Egypt, Vietnam. Personal communication, 1993.John TJ. Cost of full immunization with IPV and OPV vaccine

and treatment and rehabilitation for poliomyelitis, North Arcot Dis-trict in India (personal communication, 1991).i Grabowski M. Cost of IPV and OPV vaccine and delivery ofvaccine in the industrialized countries of the European Region(personal communication, 1992).

36 WHO Bulletin OMS. Vol 74 1996

Benefit-cost analysis of poliomyelitis eradication

reports and personal communications to establishcost parameters.

Two additional models were constructed, thefirst using 1988, the year of the World Health Assem-bly resolution on eradication of poliomyelitis, as thebase year and measuring the marginal additionalcosts and benefit-cost of moving from control ofthe disease to eradication. In the second, benefitsincluded savings in the cost of vaccine and deliveryas well as treatment and rehabilitation in order toreflect more closely the true benefits of poliomyelitiseradication.

The base case and sensitivity analyses

(1) The base case includes the identification, valua-tion and summation of the cost and benefits in eachyear of the project's life. Costs (C) and benefits (B)were summed over the years, projected and dis-counted to calculate the Net Present Value using theformula given below. The present value of thisstream of net benefits is the sum of these individualterms over the years of the model programme. In themodel, net benefits remain positive, but because ofdiscounting the benefits are smaller in future years.

n B -CNet Present Value = iB-C

i=O (l+r)

(2) Eradication of poliomyelitis is taken as thatpoint where the transmission of the causative organ-ism has ceased in an irreversible manner, vaccine isno longer in use and, as a result, cases and infec-tion have disappeared from all countries of theworld."

(3) The estimates of global population, the globalbirth cohort and the population living in industrial-ized and developing countries in each region arederived from the 1992 mid-year United Nationspopulation estimates (22). No attempt has beenmade to incorporate the growth rate into the cohortto be vaccinated.

(4) The population to be vaccinated during the rou-tine vaccination programme is estimated as the 1992

kWorld Health Organization. Certification of the global eradica-tion of poliomyelitis. Meeting of a working group. Unpublisheddocument EPI (Poliol/93.1), 1993.' The choice of vaccination schedule and vaccine (OPV or elPV)differs within and between the countries of the developing andindustrialized world. The WHO-recommended schedule of fourdoses of OPV in the first year of life is used in developing coun-tries. In the industrialized world at least five countries us elPVsolely as the primary series and at least three countries use OPVand elPV.

global birth cohort of surviving infants (133831500,of which 115272400 are in the developing world and18559100 are in the industrialized world and EasternEurope) who receive four doses of OPV during rou-tine immunization (at birth, 6, 10 and 14 weeks)during the first year of life.' It is projected that 90%of the target population is reached. In addition, chil-dren aged 13-59 months (1-5 years) who have beenidentified with incomplete vaccination during rou-tine facility-based vaccination sessions during theirfirst year of life are assumed to be vaccinated at theseroutine contacts. It is estimated that 1/5 of un-vaccinated children aged 13 to 59 months are identi-fied and vaccinated each year.

(5) Immunization coverage estimates are those esti-mated and reported by the EPI as of October 1993.Coverage estimates are for three doses of oral polio-myelitis vaccine (OPV 3), since no systematic cover-age estimate for the birth dose is available. Costs areprojected for four doses to all children, i.e., as if allinfants had received a birth dose, to maximize thecosts of the model.(6) National vaccination days are projected twice ayear for 5 years in addition to the routine vaccina-tion programme for all children aged <59 months.These are projected as two doses one month apart.It is projected that 90% of the target populationis reached during each national vaccination day.Sensitivity analyses are done for target populationsaged '<36 months and '<48 months (Table 1).(7) In addition, after 5 years of national vaccinationdays are completed, in response to the continuedoccurrence of cases, 10% of children aged -59months are projected to be vaccinated in annual"mop-up" campaigns. It is projected that 90% of thetarget population is reached during each mop-upcampaign. These are projected as two doses onemonth apart for two years. Sensitivity analyses aredone for target populations aged <36 months and<48 months, with 1% and 0.1% of all childrentargeted to be vaccinated.(8) Outbreak response is projected surroundingcases in which 1% of all children aged -<59 monthsare immunized with two doses one month apart. It isprojected that 90% of the target population isreached during outbreak response. Sensitivity analy-ses are done with 0.1% of children aged '<59 monthsvaccinated.(9) Vaccination costs are expressed in 1993 US dol-lars, and are based on the planned regional pro-grammes of eradication (Table 2). All costs aremodelled beginning in 1986. The programme for theAmericas is assumed to have begun in 1986 withnational vaccination days and outbreak control car-

WHO Bulletin OMS. Vol 74 1996 37

K.J. Bart et al.

Table 1: "Base case" costs and benefits and sensi-tivity analysis for poliomyelitis eradication pro-gramme model

I. Costs

1. Routine vaccinationa. Population s12 months old 133830000 plus 20% of

1-5-year age group (107064000)- Industrialized countries 18560000- Developing countries 115207000

b. Industrialized countriesVaccine cost - OPV US$ 4.16/dose (base case)Delivery cost - OPV US$ 5.09/dose (base case)

c. Developing countriesVaccine cost - OPV US$ 0.08/dose (base case)(Sensitivity analysis: US$ 0.12/dose)Delivery cost - OPV US$ 1.51/dose (base case)(Sensitivity analysis: US$ 3.00/dose)

d. WastageOPV 33%(Sensitivity analysis: 50%)

2. Accelerated vaccination activities (national vaccination days(NVD), mop-up, outbreak control)

a. Population s59 months age 669150000- Industrialized countries 92800000- Developing countries 576350000(Sensitivity analysis: for mop-up 1% and 0.1%;

for outbreak control 0.1%of the target population.)

b. Industrialized countriesVaccine cost - OPVDelivery cost - OPV

c. Developing countriesVaccine cost - OPVDelivery cost - OPV(Sensitivity analysis:

US$ 4.16/doseUS$ 1.48/dose

US$ 0.08/doseUS$ 0.10/doseUS$ 0.79/dose

3. Target population foraccelerated activities s59 months old (base case)(Sensitivity analysis s48 and <36 months old)

4. Discount rate 6%(Sensitivity analysis at 0%, 3%, 10%)

II. Benefits

Case of paralytic poliomyelitis - pre-EPI 5/1 00 000(Sensitivity analysis: 2/100000 and 19/100000)

Proportion of paralytic cases receiving treatment andrehabilitation

Industrialized countries 100%Developing countries 33%(Sensitivity analysis: 0%)

Cost of treatment and rehabilitationIndustrialized countriesDeveloping countries

US$ 25000/caseUS$ 250/case

ried out for 5 years until 1990, with mop-up effortsthat continued for two additional years. Routineimmunization is planned to continue till the year2005 when eradication is projected to be declaredglobally.

For the Western Pacific Region (WPR) the pro-gramme is assumed to have begun in 1991 with"subnational vaccination days" (20% of the childrenless than 5 years of age) having been carried out fortwo years prior to the first national vaccination daysin 1993. It is projected that 90% of the target popu-lation was reached during each subnational vaccina-tion day. Children were vaccinated with two dosesone month apart.

In the European Region (EUR) only one-thirdof the population are in countries expecting to con-duct national vaccination days, i.e., the former SovietUnion, the former Yugoslavia, Turkey, Romania,Bulgaria and Albania. This effort is projected tohave begun in 1992, and 90% of the target popula-tion was reached with two doses one month apart.

In the Eastern Mediterranean Region (EMR)two years of subregional vaccination days began in1992 to be followed by national vaccination days forfive years. Subregional vaccination days are definedas targeting 10% of the children aged -59 monthsfor vaccination with two doses one month apart. It isprojected that 90% of the target population wasreached.

National vaccination days began in the South-East Asia Region in 1994 although individual coun-tries e.g. India, started subnational vaccination daysin 1992. The African (AFR) Region began nationalvaccination days in 1995. It is projected that therewill be 90% coverage with two doses one monthapart.

(10) Globally, each country will be monitored forthree years by a Global Eradication CertificationCommittee after the last case of poliomyelitis hasbeen reported, and after vaccinations have beenstopped and poliomyelitis is declared as eradicatedin the year 2005. Routine immunization is projectedto continue in all regions until they are polio-free.

(11) Although an incidence as high as 32 per 100000has been reported, the global incidence of paralyticpoliomyelitis at the outset of the eradication effort isestimated conservatively at 669158 or 5 per 100000surviving newborns.

(12) It is assumed for the purposes of this calcula-tion that, in industrialized countries, 95% of thosevaccinated with OPV were immunized, i.e, devel-oped detectable levels of neutralizing antibodies(23). In developing countries it is assumed that 80%of those vaccinated with OPV were immunized.From the limited data available, seroconversionrates with OPV during national vaccination daysmay be 10% higher than during routine immuniza-tion programmes, but this is not taken into accountin these calculations.

WHO Bulletin OMS. Vol 74 199638


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K.J. Bart et al.

(13) Analysis of secular trends in countries wheresubstantial coverage has resulted in a significantreduction in disease demonstrates that with rou-tine immunization programmes cases fall at anestimated 40% per year. With mass campaigns thereduction is estimated at 70% per year. The pro-jected decline in cases with the continued appli-cation of vaccine is projected linearly for ease ofpresen-tation. At the end of the programme 669158patient-cases are projected to have been preventedworldwide annually.

(14) Programme costs, treatment and rehabilitationcosts, and vaccine costs are stratified by developingand industrialized countries and are presented in1993 US dollars.

(15) The cost of acute care and subsequent rehabili-tation is conservatively assumed to be US$ 25000per case in industrialized countries and US$ 250 percase in developing countries. The base case assumesthat only one-third of all cases in developing coun-tries receive acute care and rehabilitation; 100% ofcases are assumed to receive treatment and rehabili-tation in industrialized countries. A sensitivity analy-sis is done assuming that only 10% of cases indeveloping countries receive acute care and rehabili-tation; and that 0% of cases in developing countriesand 75% in industrialized countries receive treat-ment and rehabilitation.

(16) The expenses of poliomyelitis vaccination,which are derived from studies sponsored by theexpanded programme on immunization (EPI), arethe result of summing capital costs (buildings, vehi-cles, refrigeration and the cold chain), operationalcosts (including staff salaries, supervision), and thecost of transport (including fuel and spare parts).Only the costs to the delivery system are used in thismodel. In addition to the costs of purchasing anddelivering vaccine, additional resources are neededto effect eradication such as training, increasedsurveillance activities; improvements in the coldchain; improved laboratory support; data collectionand processing, etc. Since the largest portion ofthe costs are due to vaccine and delivery, theseadditional costs are not included to streamline themodel.

(17) For simplicity of the model it is assumed that allcountries use only OPV, the WHO-recommendedvaccine of choice. The cost of OPV for the pro-gramme in developing countries at 1993 UNICEFprices is US$0.08/dose at port of entry. Sensitivityanalysis is done with OPV vaccine costs usingUS$0.12/dose (a 50% increase as an estimate of fu-ture inflation). In industrialized countries the aver-age cost of OPV is US$4.16/dose.

(18) The cost of vaccinating a child in the devel-oping world with OPV is estimated at US$1.51/dose. A sensitivity analysis is done at US$3.00.This is based on the EPI estimates that in thedeveloping world the delivery system costs areestimated to be US$15.00 to fully immunize achild. Assuming OPV is given at 4 of the 5 visitsrequired to fully immunize a child, the cost offully vaccinating a child with OPV is estimated to befour-fifths of US$15.00/child. In order to fullytest the benefit-cost relationship, the cost of vac-cinating a child with all vaccines during each ofthese four visits is attributed to poliomyelitis,i.e., US$3.00/visit. For industrialized countries, esti-mates for the delivery of vaccine are estimated atUS$ 5.09/dose.

(19) Based on EPI estimates, the cost of deliveryduring national vaccination days, mop-up and out-break response activities in a developing country isUS$0.10 per dose. A sensitivity analysis is done atUS$ 0.79/dose. In industrialized countries the cost ofa contact is US$1.48/dose. A sensitivity analysis isdone at US$2.47/dose.(20) The estimate of the benefits of poliomyelitiseradication takes no account of the reduced painand suffering or deaths due to poliomyelitis, thegreater productivity of individuals who wouldotherwise be paralysed and become unproductive,the improved quality of life, or the reduction ofother vaccine-preventable disease that could be ex-pected to result from a successful programme againstpoliomyelitis.(21) As an additional model, eradication of the267663 cases (2 per 100000, down from 5 per100000) estimated to be occurring in 1988, theyear of the World Health Assembly resolution onglobal eradication of poliomyelitis, is taken torepresent the marginal additional costs to movefrom a routine vaccination programme directedat control of the disease to one directed towardseradication.(22) To explore further the full net present valueof eradication, a second additional model is pro-jected, adding the costs of vaccine and delivery tothose of treatment and rehabilitation as items ofbenefit.(23) Costs and benefits are discounted at 6% annu-ally. A sensitivity analysis is done at 0, 3 and 10%.

(24) Vaccine wastage is estimated at 33%. A sensi-tivity analysis is done at 50%.(25) While vaccine-associated poliomyelitis can, inindividual cases in industrialized countries, rarely beassociated with substantial treatment and litigation



costs, and since the rate of vaccine-associated polio- Fig. 1. Global poliomyelitis eradication model: basemyelitis is so low, vaccine-associated poliomyelitis case.has not been included in these calculations.

(26) The costs of treatment, rehabilitation and vac- 15cination will end at eradication, and the net benefits CD

accrued are estimated beyond the year 2007 for a xtotal of 55 years. , 9 /

Results _24- 3 -20070 8 \X/ BenefitThe base case C BenefiteQ ~~~~~~~~~~~Cost

Using the assumptions and parameters described, > 3 \the net costs and benefits of the global eradication of /poliomyelitis were calculated for a period of 55 years E --Ofrom 1986 to 2040. As shown in Table 3, the costs oexceed the net benefits in 2007, at a base case dis- -9count rate of 6%. By the year 2040, the saving will 1980 1990 2000 2010 2020 2030 2040amount to US$ 13640 million. Year

Table 3: Net costs or benefits of global poliomyelitis eradication: base case and sensitivity analyses, for the year2040

Costs or Year whenbenefits in 2040 benefits(US$ millions) exceed costs

Base case 13640 2007

11 Sensitivity analysesa. Target age of accelerated activities (base case 659 months):

636 months 16310 2005s48 months 14970 2006

b. Proportion of target age reached by mop-up (base case 10%):1.0% 14240 20070.1% 14260 2007

c. Cost of routine vaccine (OPV) and delivery (base case is US$ 0.08):Developed countries US$ 3.00 13690 2007Developing country US$ 0.12 3790 2024

d. Cost of accelerated activities/contact:Developing country US$ 0.79 11 270 2010

(Base case US$ 0.10)Industrialized country US$ 2.47 13480 2008(Base case US$ 1.48)

e. Access to treatment and rehabilitation (base case 33% for developing and100% industrialized):10%/100% 13480 20070/100% 12870 20080/75% 3070 2023

f. Vaccine wastage (base case is 33%)50% 10210 2011

g. Discount rate (base case is 6%)0% 86130 20043% 34500 200510% 1850 2017

111 Additional modelsa. Treatment and rehabilitation plus vaccine and delivery 27360 2005b. Acceleration from control to eradication (base case 5/100000) 11 440 2010

2/100000 to zero (treatment and rehabilitation plus vaccine and delivery) 3380 2026


K.J. Bart et al.

The net cumulative cost or benefits of the basecase are shown in Fig. 1 in millions of US dollars.Each data point represents the net cumulative costsor benefits for the model programme to that date.The slope of the line falls as a result of net costsincreasing as each of the Regions begins its acceler-ated vaccination efforts. In the year 2000 the benefitsof the programme are seen as the number of avertedcases increase, and the curve begins to turn upwards.For the base case, the year 2007 is the break-evenpoint, the year in which the savings exceed the pro-gramme costs. From this point on, the benefits of theprogramme exceed the costs in every year, and thenet benefits continue to increase. This increase con-tinues after the planned end of the eradication effortsince the benefits of eradication continue beyond theprogramme, i.e., through cases prevented and sincetreatment and rehabilitation are no longer needed.

As seen by the plateau of the curve, althoughthe benefits of eradication continue in perpetuity (nocases with the attendant costs are occurring, andthere is no longer any requirement to vaccinate), thedollar benefits decrease substantially as a result ofdiscounting.

Sensitivity analysis

When alternative assumptions were tested, theeradication of poliomyelitis was still shown to becost-beneficial. Different assumptions about the dis-count rate, the proportion of cases receiving treat-ment and rehabilitation, vaccine wastage, the ageand proportion of the target population vaccinatedduring accelerated activities, and the cost of deliver-ing immunization services may modify the results ofthe base case, but do not significantly alter them.

Target age of accelerated activities. Alternative tar-get ages of accelerated immunization activities wereevaluated. The base case assumes the target age is-59 months. The shortage of resources to purchasevaccine has the potential to force a lowering of thetarget age group for accelerated activities as wasthe case in China in 1992. For all target age groupseradication is cost-beneficial. Each year of loweringof age group in the target population to be vac-cinated decreases the year of breaking even by oneyear: for the base case (-59 months) the break evenyear is 2007; for -48 months it is 2006, and for <36months it is 2005.

Cost of vaccine and delivery. The effect of an in-crease in OPV price from US$0.08 to US$0.12 hasno significant impact on the year of breaking even orthe overall slope of the curve (Table 2). Increasingthe costs of delivering OPV by nearly eightfold in

developing countries (US$ 0.79) had the effect ofonly delaying the year of breaking even by two years(Table 2).

Access to treatment and rehabilitation. The impact ofvarying the assumptions about access to treatmentand the availability of rehabilitation in both develop-ing and industrialized countries are assessed. Fig. 2compares the base case (33%) with the overall im-pact of a reduction in treatment and rehabilitationrates to zero percent in developing world children.Little impact is seen on the shape, slope or break-even year. At zero percent of the developing world'schildren and 75% of the industrialized world'schildren reaching treatment and receiving rehabilita-tion, it is still cost-beneficial to eradicate poliomyeli-tis. The minimal treatment and rehabilitation rateat which eradication leads to savings is 0% accessin developing countries and only 60% of childrenin industrialized countries receiving treatment andrehabilitation.

Vaccine wastage. The effect of vaccine wastage onnet costs and net benefits is tested by increasing thevaccine wastage rate from the base case 33% to 50%.

Fig. 2. Global poliomyelitis eradication: varying treat-ment rate assumptions in developing and industrial-ized countries. Base case: in developing countries, 33%of acute poliomyelitis patients received care and rehabili-tation; in developed countries, 100%. Sensitivity analyses:0%/100% - no acute poliomyelitis patients receive carein developing countries, while 100% do so in industrializedcountries; 0%/o/75% - no acute poliomyelitis patients re-ceive care or rehabilitation in developing countries, while75% do 80 in industrialized countries. The year in paren-theses is the break-even year.

15 Base case: 33% and 100%o 12 (2007)x %00%IlO%_0 9 (2008)

6

6 3§0%!75%(2022)

030 0

c -3

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While this increase delays the time when net costsare exceeded by net benefits from the year 2007 to2011, eradication remains cost-beneficial.

Proportion of the target population reached duringaccelerated activities. Reducing the population cov-ered by mop-up and outbreak response from 1% to0.1% had no significant effect on whether eradica-tion or the year of breaking even is cost-beneficial, ascompared to the base case (Table 2).

Discount rate. The effect of alternative discountrates is shown in Table 2. At a 3% discount rate, thebreak-even point is two years earlier as compared tothe base case at 6% in the year 2007. Discount ratesof 0% and 10% demonstrate a family of curves, all ofwhich are cost-beneficial with break-even points be-tween 2004 and 2017. The rate of 3% is more com-monly used for social sector programmes such aspoliomyelitis eradication. At 3% the net savings willbe US$ 34 500 million by the year 2040.

Additional models

Addition of the cost of vaccine and delivery to the costof treatment and rehabilitation as benefits. The an-nual global cost of routine vaccination with OPVunder the base-case assumptions, which includes thecost of vaccine, delivery and wastage, is US$1774million. If the costs of routine vaccination (vaccineand delivery costs) are added to the cost of treatmentand rehabilitation as benefits accrued from eradica-tion, the year of breaking even is 2005, two yearsearlier than for the base case (Table 2), and precedesthe year of the declaration of eradication, whichmakes the eradication even more cost-beneficial.

Marginal additional costs of accelerating from controlto eradication. After the World Health Assemblyresolution (WHA41.28) had established the goal ofglobal eradication of poliomyelitis, there was con-cern about the diversion of resources from primaryhealth care development and other priority dis-ease control activities towards eradication activities.Routine administration of OPV had reduced casesfrom an estimated 5/100000 to 2/100000 in 1988,the year of this resolution. This level would be ex-pected to be maintained if there was no accelerationof activities towards eradication. Reducing casesfrom 2/100000 to zero represents the marginal addi-tional cost of moving from control to eradication.The base case is compared with the acceleration ofthe programme beginning in 1988. Similar to thebase case model, the benefits accrued were modelledin terms of treatment and rehabilitation alone, and

treatment and rehabilitation plus vaccine and de-livery costs. When the combined costs are tested,beginning with the level of 2 cases per 100000, anaccelerated programme is cost-beneficial, and movesthe break-even point to the year 2026. Poliomyelitiseradication, whether modelled from pre-eradicationto eradication or as an acceleration from rou-tine immunizations after the substantial initialimpact, is cost-beneficial and saves US$ 3380 million.(Table 2).

DiscussionIn spite of systematic underestimation of the benefitsof a poliomyelitis eradication programme, there isevidence of positive and high returns from such aninvestment; the base case demonstrates that the netbenefits exceed the net costs of the programme onlytwo years after eradication is declared. By the year2040, the savings will be US$ 13600 million. Polio-myelitis eradication, through sensitivity analysis andunder the most stringently unfavourable test condi-tions, is economically beneficial, and the break-evenpoint is always close to the date of eradication. Thisis true under various assumptions- increase in costof vaccine and delivery, high vaccine wastage, lim-ited access to treatment and rehabilitation, limitedtarget age groups for accelerated activities, and highdiscount rates. The world would therefore not haveto wait many years for eradication to pay off.

The eradication of poliomyelitis is a justifiableinvestment even without making any allowance forsavings (benefits) other than those due to real reduc-tions in expenditures to treat and rehabilitate someof the victims of the disease. Morbidity in the formof a post-poliomyelitis handicap affects a child'sactivity throughout life. This loss is associated withboth real and intangible costs (missed work, un-employment, family loss of work time and income,reduction in anxiety, pain and the social stigma ofhandicaps). The cost of treating even a small fractionof those who need treatment and rehabilitation islarge enough to pay for the total prevention of polio-myelitis. The addition of vaccine and delivery costs,which will cease after eradication, makes the tan-gible saving even larger- an additional annual sav-ings of US$ 1700 million.

Experience with poliomyelitis epidemiologyand with elimination of poliomyelitis in the Ameri-cas has demonstrated that eradication is technicallyfeasible. Like smallpox, humans are the only reser-voir of the virus, and there are no long-term carriers.An effective and inexpensive vaccine is readily avail-able. While the ease of poliovirus transmission andthe high infection-to-case ratio would suggest thatthe virus potentially is difficult to contain, little evi-


K.J. Bart et al.

dence of this as an impediment has appeared in theAmericas. Discussions of poliomyelitis eradicationno longer include questions of feasibility, but ratherfocus on the extent to which eradication efforts coulddivert resources from interventions that would havea potentially greater health impact, or could inter-fere with the development of primary health care.

One technical controversy is related to EPI'scontinuous process of resolving programmatic is-sues. Discussions revolve around specific operationaland implementation issues including the difficultiesof seroconversion using OPV in tropical countries;the utility of outbreak response interventions; thefeasibility of dependence on mass vaccination in allregions of the world; the appropriate target age formass vaccination (',59 months of age versus 636 or648 months of age); and the requirement for mop-up operations in large areas. All these have beenshown in this analysis not to affect the benefit-costrelationship, but only to lower or to extend thebreak-even year briefly.

Extension of the techniques used in the Ameri-cas to the other regions of the world where there arelower seroconversion rates with OPV, persistingcold chain problems, and less developed infrastruc-tures continues to draw attention. The experiences inthe Americas, however, suggest that these issues arenot insurmountable, and we have now the opportu-nity to pursue the global eradication of a seconddisease of unacceptable morbidity and mortalityafter smallpox.

This analysis is based on a relatively rapid im-plementation of the overall eradication effort, withtime limits for the implementation of eradicationstrategies between regions. If there is a major delayin either, then the threat of imported cases, continu-ing epidemics, and the need for more national vacci-nation days and mop-up activities will increase thecost of eradication substantially and the earlier ben-efits will be lost. A gradually increasing programmewill clearly be more costly and will be a suboptimalstrategy.

This model demonstrates that the eradication ofpoliomyelitis will make money available for otherhealth programmes. Individuals and other parts ofthe health care system will benefit from poliomyelitisimmunization in addition to the vaccinated chil-dren, the general reduction in the risk of infectiongiving all those at risk some benefits. Other externalbenefits stem from the institutional changes thataccompany the increased accessibility, perform-ance and credibility of effective health services.Instead of competing with the primary healthcare services, the eradication programe fostersthe development of primary health care through afocused approach and the strengthening of man-

agerial and other capacities of the primary healthcare system.

The acceleration from a routine programme toan eradication programme also demonstrated a fa-vourable benefit-cost ratio with the expansion fromthe more limited inputs associated with control tofull eradication. The public health strategy of diseaseeradication offers considerable advantages over dis-ease control. The benefits of eradication are perma-nent and accrue long after the finite costs cease,while the costs of controlling the same disease mustbe maintained indefinitely.

The availability of an easily administered, inex-pensive vaccine in OPV, the characteristics and epi-demiology of poliomyelitis, and the experience in theAmericas with successful elimination of wild polio-myelitis support the technical feasibility of eradica-tion of poliomyelitis. These analyses demonstratethat poliomyelitis eradication is economically justi-fied. Continuing delay in implementation will bothincrease the cost of achieving eradication and under-mine past achievements. Sustained national and in-ternational support can be expected to lead toeradication and to generate significant savings fornational governments.

ResumeEradication mondiale de lapoliomyelite: analyse du rapport co-ut/avantagesUne analyse coOt/avantages a ete entreprise pourfaciliter la prise de decisions financieres a l'echelonnational et international en vue de l'eradicationmondiale de la poliomyelite. Seules les 6conomiessur le coOt du traitement et de la r6adaptationr6sultant de la r6duction de l'incidence de lamaladie ont ete prises en compte dans I'analysedu sc6nario de base. Si l'on peut montrer quel'eradication presente un rapport coOt/avantagesfavorable sans tenir compte de toutes les autreseconomies tangibles ni des avantages intangiblesou indirects, on peut s'attendre a un rapport encoreplus favorable si tous ces avantages sont pris enconsid6ration.

Le sc6nario de base envisage une populationcible constituee de tous les enfants du monde ag6sde 59 mois et moins (133 830 000); il suppose aussique le coOt du vaccin et de son administration n'estpas le meme dans les pays industrialises et dansles pays en d6veloppement, et que le taux degaspillage du vaccin est de 33%. Les coOts duvaccin et de son administration ont ete determinespour des campagnes de vaccination acc6l6rees(journees nationales de vaccination, activit6s deratissage et reponse aux epid6mies); les avantages



et les coOts ont 6t6 actualises au taux de 6%.Des analyses de sensibilit6 ont 6t6 effectuees

pour des populations cibles d'enfants d'age dif-f6rent (-36 mois, <48 mois et -59 mois), pourdiff6rents taux d'actualisation (0%, 3%, 6% et 10%),pour diff6rents taux de couverture du traitement etde la r6adaptation dans les pays en d6veloppement(33%, 10% et 0%) et dans les pays industrialis6s(100%, 75% et 60%), pour diff6rents coOts d'ad-ministration du vaccin dans les pays en d6velop-pement (US $0,10 et US $0,79/dose), et pourdifferents taux de gaspillage (33% et 50%).

Pour chacune des annees du modele, on aestim6 le nombre de cas de poliomy6lite paralytique6vit6s, le coOt du traitement et de la readaptation,le coOt des efforts d'6radication et les avantagesnets. Les coOt totaux annuels ont et6 compar6s auxavantages totaux pour 1'ensemble de la periode,depuis la pre-6radication jusqua l'radication finale.En outre, un autre modele a ete etabli pour evaluerla difference entre le coOt des activites de luttecontre la poliomyelite et le coOt de l'6radication.

A partir des hypotheses et des parametres duscenario de base, on a 6valu6 le coOt ou le ben6ficenet de l'radication mondiale de la poliomy6lite pourune periode de 55 ans allant de 1986 a 2040. Laconclusion a ete que le rapport coOt/avantages6tait favorable. Selon le modele, les coOts d6pas-seraient les avantages en 2007, mais en 2040, les6conomies s'6leveraient a US $13600 millions.Dans toutes les hypotheses retenues pour I'analysede sensibilit6, les avantages d6passeraient lescoOts du programme quelques ann6es au maxi-mum apres l'radication.

L'existence d'un vaccin peu coOteux et facile aadministrer (VPO), les caracteristiques 6pid6mio-logiques de la maladie et le succes de l'liminationdu virus sauvage dans les Am6riques permettentde penser que l'radication mondiale de la polio-my6lite est techniquement realisable. Les analysesdecrites dans le present article montrent qu'elle sejustifie du point de vue 6conomique.

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