In September 1994, the International Commission for the Certification of Poliomyelitis in the Americas certified that transmission of wild poliovirus had been interrupted in the western hemisphere [3]. By October 1996, more than 5 years had passed since the last confirmed case of paralytic poliomyelitis caused by wild poliovirus was detected on 23 August 1991 in Peru. This is an historically significant event in the annals of public health.

The eradication of poliomyelitis from the Americas was made possible by great commitment and allocation of natural resources on the part of the governments of all countries involved, a sound epidemiologic strategy, and well-coordinated international support to aid national efforts. Under the leadership of PAHO, such organizations as UNICEF (United Nations Children's Fund), the U.S. Agency for International Development, the Inter-American Development Bank, the Canadian Public Health Association, and Rotary International worked together to support national efforts [4].

The strategies developed during this campaign are now being implemented worldwide to eradicate poliomyelitis globally by the year 2000 [5]. According to reports from the World Health Organization (WHO), fewer than 5000 cases of poliomyelitis throughout the world were reported in 1996-the lowest number ever reported. The target of global eradication by the year 2000 is well within our reach. By October 1996, almost every country in the world to which poliomyelitis is endemic was engaged in activities intended to eradicate poliomyelitis. Major international support was forthcoming, particularly from the governments of the United States, Japan, the United Kingdom, and Denmark, to cite a few.

Still, much remains to be done if the goal is to be reached. Financial support equivalent to approximately $500 million is needed between now and the year 2000 to eradicate poliomyelitis globally. However, the benefits will be enormous. No child will ever again be paralyzed from or die of this dreadful disease, and WHO estimates that the equivalent of $3 billion will be saved annually worldwide after polio is eradicated. These financial resources can then be used to tackle other health problems. The experience in the Americas has also shown that the health care infrastructure has benefited greatly from the effort to eradicate poliomyelitis and is now better prepared to control or eradicate other infectious diseases [6].

One such disease is measles. Although an excellent vaccine has existed for more than three decades, measles still kills more than 1 million children annually worldwide. With poliomyelitis eradicated from the Americas, PAHO has targeted measles to be eradicated from the western hemisphere by the year 2000. The strategies recommended to achieve this goal include national immunization campaigns conducted in a short period of time (usually 1 month) to immunize all children between 1 and 14 years of age (regardless of previous vaccination status) and maintenance of high immunization levels in each new cohort of infants. These strategies, which aim to interrupt all chains of transmission, are followed by intense surveillance for suspected cases of measles, prompt investigation of reported cases, and collection of blood specimens for laboratory diagnosis [7]. A network of 12 measles reference laboratories in 11 countries, organized by PAHO, supports the work of all national laboratories involved in the diagnosis of measles.

As a result of the initial implementation of this strategy, only 1680 confirmed cases of measles were reported in 1996; this is the lowest number of measles cases reported since surveillance began in the Americas. In the 1980s, an average of more than 150 000 cases were reported annually in the western hemisphere. In the English-speaking parts of the Caribbean, it has been more than 5 years since the last laboratory-confirmed case of measles occurred, and no cases of measles have been reported for the past 3 years in Cuba and Chile. Measles surveillance systems are now in place in every country of the Americas, and no evidence of the circulation of measles virus has been found in most countries in this region [8].

One obstacle to eradicating measles is the accumulation of susceptible children 1 to 4 years of age. It is difficult to vaccinate all of the children in this age group, and the efficacy of the vaccine is not 100%. To immunize these children and prevent out-breaks, PAHO recommends that countries conduct follow-up vaccination campaigns every 4 to 5 years that target all children who are 1 to 4 years of age, regardless of previous vaccination status [7]. These campaigns offer an opportunity for children who were never vaccinated to receive a first dose of measles vaccine and for most children to receive a second dose and boost their immunity to measles. This is also an opportunity to revaccinate the few children who were vaccinated but did not respond to the vaccine.

A second obstacle to eradicating measles in the Americas is the high incidence of measles in other regions of the world; international travel occasionally causes the virus to be imported from those areas. In 1995, 60% of the 309 cases of measles reported in the United States were either directly imported or were found to be linked to an imported case by routine investigation or molecular epidemiology methods [9]. In the past 2 years, not one case of measles was imported from Latin America or the Caribbean to the United States. This indicates that measles is now very rare in those areas.

A meeting of experts convened in July 1996 by WHO, PAHO, and the Centers for Disease Control and Prevention concluded that measles can be eradicated with the existing vaccine if political will is mustered and if proper strategies, such as those recommended by PAHO, are implemented [10]. The continued success of measles eradication in the Americas will set the stage for the global eradication of this disease; the target date for the achievement of this goal should be the end of the first decade of the 21st century.

Nearly 200 years have passed between Jenner's development of the smallpox vaccine and the eradication of this disease. It is now almost 40 years since Sabin developed the oral poliomyelitis vaccine, which led to eradication of the disease from such a vast area as the western hemisphere. This, in turn, set the stage for global eradication of poliomyelitis by the year 2000. It now seems that approximately 50 years will have passed between Enders' development of the measles vaccine and the eradication of measles. It is incumbent upon us, as physicians and health practitioners, to advocate the prompt use of technologies that save human lives as soon as they become available. The biotechnology revolution will make the 21st century the century of vaccines. Vaccines are among the most effective and cost-effective instruments available to us for the promotion of public health, but their use must be accompanied by an even more fundamental revolution in which preventive medicine rates high in governmental priority setting and allocation of limited resources. Only then will humankind benefit from these scientific and technological developments, as was the case with the eradication of smallpox and as should be the case with the eradication of poliomyelitis and measles in the near future.