Disease eradication as a public health strategy : is measles next? / Jean-Marc Olivé, R. Bruce Aylward & Bjorn Melgaard

Disease eradication as a public health strategy: is measles next? Jean-Marc 0/ivea, R. Bruce Aylwardb & Bjorn Melgaardc Disease eradication as a public health strategy Since the turn of the 20th century, 6 major initia- tives have been launched to eradicate infectious diseases, targeting yellow fever, yaws, malaria, smallpox, poliomyelitis and dracunculiasis. Follow- ing the ultimately unsuccessful conclusion of the first 3 efforts, support for eradication programmes waned, particularly as attention shifted to improv- ing basic health services worldwide, a pursuit felt by many to be incompatible with the 'vertical' nature of eradication ( 1 ). The successful smallpox eradica- tion programme, however, and the progress of the ongoing initiatives against poliomyelitis and dra- cunculiasis have somewhat rehabilitated the con- cept of disease eradication ( 1 ). There is increasing evidence that, in addition to eliminating an infec- tious disease and its related costs, such pro- grammes can substantially benefit health services in general (2, 3). The prominence of recent eradication initia- tives has led some to promote the concept as a public health strategy, calling for similar initiatives to be launched against other diseases of public health importance. In a number of countries, political leaders, health authorities and the general public are increasingly suggesting that measles, the lead- ing cause of vaccine-preventable childhood mor- bidity and mortality, should be the next organism targeted for eradication. Measles as a public health problem Despite the widespread opinion that measles con- stitutes a 'normal' disease of childhood, nearly 10% of the mortality among children aged less than 5 years worldwide is due to this disease (Fig. 1) ( 4 ). In 1996 alone, it was estimated that over 1 million children died of measles or one of its complications (5). The majority of this mortality is taking place in the world's poorest countries, par- ticularly in sub-Saharan Africa where a combina- tion of factors such as crowding, a lower age at a Medical Officer, Expanded Programme on Immunization, Global Programme for Vaccines and Immunization, World Health Organization, Geneva. b Scientist, Expanded Programme on Immunization, Global Programme for Vaccines and Immunization, World Health Organization, Geneva. E-mail: aylwardb@who.ch c Chief, Expanded Programme on Immunization, Global Programme for Vaccines and Immunization, World H ealth Organization, Geneva. Wld hlth statist. quart., 50 (1997) Fig. 1 Distribution of 12.2 million deaths among children aged less than 5 years in all developing countries, 1993 Repartition des 12,2 millions de deces parmi les enfants de mains de 5 ans dans les pays en developpement, 1993 Malaria (ARI) Paludisme (IRA) 1.6% Malaria Paludisme 6.2% Others Autres 33% Acute respiratory illness (ARI) Infection respiratoire aigue (IRA) 26.9% \ Measles (diarrhoea) Rougeole (diarrhee) 1.9% WH097494 exposure and, possibly, malnutrition contribute to substantially higher case-fatality rates than seen in industrialized countries (6). In some developing countries, measles case-fatality rates still reach over 10%, especially during outbreaks (7). Even in industrialized nations, measles con- tinues to cause considerable morbidity, the eco- nomic consequences of which can be substantial (8). In many of these countries, the financial costs of measles-related treatment and lost productivity alone have been a major factor in decisions to pursue a very high degree of control of the disease. In the mid-l 990s, cost-effectiveness studies in the United Kingdom and Canada demonstrated the fiscal advantage of undertaking supplementary immunization activities to prevent nationwide measles epidemics (9, 10). A new direction: measles outbreak prevention and elimination The decision to target a disease for global eradica- tion is based on a number of biological, epidemio- logical, social, political and economic factors (]). Of particular importance is the demonstration that control strategies can eliminate the organism over a wide geographical area for a sustained period of time. Although several industrialized countries adopted measles elimination goals in the 1970s, few managed to interrupt transmission for pro- longed periods due to either the strategies chosen 185 or the operational constraints in their implemen- tation. Much of the recent interest in measles eradica- tion is the result of the progress toward regional elimination of the disease in the Americas. Build- ing on the success of the regional polio eradication initiative and experience with measles elimination in Cuba, Chile and the English-speaking Carib- bean, the 1994 Pan American Sanitary Conference adopted a goal of regional measles elimination by the year 2000. The strategy combined a one-time mass campaign for all children aged 9 months to 14 years with high routine immunization coverage and regular catch-up campaigns ( 11). Following the widespread implementation of this strategy, the number of reported measles cases fell from 49 OOO in 1993 to less than 2 200 in 1996, the lowest number ever reported in the Region. This decline occurred despite marked improvements in surveil- lance, including the introduction of IgM testing of all suspected measles cases. Outside the Americas, an increasing number of industralized and developing countries have adopted aggressive measles control goals ranging from outbreak prediction and prevention to na- tionwide interruption of transmission (5, 12). In the United Kingdom, for example, a nationwide measles-rubella campaign was conducted in 1994 to prevent an outbreak that was predicted for the following year. Similar strategies have been em- ployed in countries of southern Africa, the Eastern Mediterranean, South-East Asia and the Western Pacific. Global eradication at measles: unanswered questions Despite the interest in a global measles eradication initiative, a number of issues remain to be resolved. Additional observation is needed to determine whether the successful interruption of transmis- sion in many countries of the Americas can be sustained despite the regular reintroduction of the virus from other regions and the gradual but inevi- table increase in susceptible individuals. The oc- currence of a large urban outbreak in both the child and adult populations of Brazil in 1997 dem- onstrated that widespread circulation can be quick- ly re-established if the virus is reintroduced into a population whose level of susceptibility has been allowed to exceed the epidemic threshold of the disease ( 13). High quality surveillance is needed not only to identify rapidly and investigate infected areas, but to determine the accumulation and dis- tribution of measles-susceptible individuals in a population in order to guide routine and supple- mentary immunization activities. A concerted effort will be needed to demon- strate the benefits that a global eradication initia- tive holds for countries where there has been a very low burden of measles-related disease for many 186 years. High level commitment within the political, medical and general communities of industrialized countries in particular would be essential to ensur- ing that the appropriate strategies were fully imple- mented and that sufficient resources are available. At least US$1 billion would be needed in external support over a 5-10 year period to facilitate measles eradication in developing nations. Of particular importance to the future of a measles eradication effort is the successful conclu- sion of the ongoing polio eradication initiative. Not only will such an achievement ensure the man- agement, immunization and surveillance infra- structure needed to eradicate measles, but it will further strengthen the political support required at all levels for a new eradication initiative. As dem- onstrated in the Americas, the introduction of measles elimination activities soon after polio transmission has been interrupted may play an im- portant role in sustaining high quality poliovirus surveillance after the disease has disappeared ( 11 ). Regardless of the target disease, robust mecha- nisms must be established to ensure that the im- pact of such initiatives on health services in general can be monitored and optimized. Conclusion There is increasing evidence that the sustained interruption of measles transmission is possible with existing vaccines (12). However, questions concerning the optimal immunization strategies for countries with differing levels of measles con- trol and economic development must continue to be addressed. Immunization and surveillance pro- grammes worldwide must be strengthened to en- sure that there will be a minimal accumulation of susceptibles between mass campaigns. The politi- cal commitment and both human and financial resources that are needed to launch a globally co- ordinated effort must be identified. The eradication of measles offers an oppor- tunity to achieve a substantial and permanent im- pact on worldwide childhood morbidity and mor- tality. Although this goal now appears biologically and epidemiologically feasible, before launching a global initiative, further attention must be given to the remaining social, political and financial ob- stacles to ensure that the benefits of such an initia- tive would ultimately be realized. Summary Following the failure of disease eradication efforts in the first half of this century, the success of smallpox eradi- cation and the ongoing initiatives against poliomyelitis Rapp. trimest. statist. sanit. mond., 50 (1997) and dracunculiasis are re-establishing eradication as a viable disease control strategy. The perpetual benefits of eradication, together with the positive impact that such initiatives can have on health services in general, are changing the world's perception of these endeav- ours. Among the most obvious examples of this chang- ing trend is the recent enthusiasm in both industrialized and developing countries for re-exploring the eradica- bility of measles. Increasingly, it appears that measles, the single leading cause of vaccine-preventable child- hood morbidity and mortality worldwide, may be the next major organism targeted for global eradication. Resume L 'eradication en tant que strategie de sante publique: bientot la rougeole ? Apres l'echec des efforts d'eradication de la maladie au cours de la premiere moitie de ce siecle, le succes de !'eradication de la variole et des initiatives en cours contre la poliomyelite et la dracunculose fait a nouveau de !'eradication une strategie viable de lutte contre la maladie. Le caractere definitif de !'eradication et ses avantages, et !'impact positif que ces initiatives peuvent avoir sur les services de sante en general, sont en train de modifier la fa9on dont ces efforts sont per9us dans le monde. Parmi les exemples les plus flagrants de cette evolution, on denote l'enthousiasme manifeste recem- ment par les pays industrialises comme les pays en developpement desireux de reconsiderer «l'eradicabi- lite» de la rougeole. De plus en plus, ii semble que la rougeole, principale cause de morbidite et de mortalite evitable par la vaccination de l'enfant, pourrait bien etre la prochaine cible d'une campagne mondiale d'eradi- cation. 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