Measles eradication: recommendations from a meeting cosponsored by the World Health Organization, the Pan American Health Organization, and CDC.
Recent successes in interrupting indigenous transmission of measles virus in the Americas and in the United Kingdom prompted the World Health Organization (WHO), Pan American Health Organization (PAHO), and CDC to convene a meeting in July, 1996 to consider the feasibility of global measles eradication. Presentations at the meeting included an overview of global measles control and elimination efforts; detailed reviews of successful measles elimination efforts in Latin America, the English-speaking Caribbean, Canada, and the United States; surveillance for clinical disease; laboratory tools for antibody detection and virus identification; and other factors that might influence the feasibility of disease eradication. With this background information, meeting organizers asked participants to address five questions: 1) Is global measles eradication feasible? 2) Is measles eradication feasible with current vaccines? 3) What are the appropriate vaccination strategies for measles eradication? 4) How should surveillance for measles be carried out? 5) What role should outbreak control play in the strategy to eliminate measles? Participants agreed that measles eradication is technically feasible with available vaccines and recommended adoption of the goal of global eradication with a target date during 2005-2010, with the proviso that measles eradication efforts should not interfere with poliomyelitis eradication but should build on the successes of the global Poliomyelitis Eradication Initiative. Although existing vaccines are adequate for eradication, vaccination strategies that rely on administration of a single dose of vaccine are not. In the Americas, sustained interruption of indigenous measles virus transmission has been achieved through a three-tiered vaccination strategy that includes a) "catch-up" vaccination of all persons aged 1-14 years, regardless of disease history or vaccination status; b) "keep-up" vaccination of > or = 90% of children in each successive birth cohort at age 12 months and c) "follow-up" campaigns designed to vaccinate all persons within a specific age range whenever the number of susceptible persons in the preschool-aged population approximates the size of a typical birth cohort (in practice, every 3-5 years). In other regions, different strategies may be optimal. Surveillance, a critical component of any strategy to eliminate or eradicate measles, has two functions: to assess the effectiveness of the measles elimination strategy and to detect circulation of measles virus in a population. Systematic surveillance based on clinical diagnosis should be implemented early in any measles elimination program. In countries attempting to eliminate indigenous measles, all isolated cases of measles and at least one case in each chain of transmission should be confirmed by laboratory tests. Specimens for virus isolation (e.g., urine, nasopharyngeal swabs, or blood) should be collected in conjunction with field investigations. Vaccination campaigns generally have not proved to be effective responses to measles outbreaks. Outbreaks should be treated as opportunities to reinforce surveillance and to identify measures to prevent future outbreaks. The major obstacles to measles eradication are not technical but perceptual, political, and financial. Measles is often mistakenly perceived as a mild illness. This misperception, which is particularly prevalent in industrialized countries, can inhibit the development of public and political support for the allocation of resources required for an effective elimination effort. The disease burden imposed by measles should be documented, particularly in industrialized countries, so that this information can be used to educate parents, medical practitioners, public health workers, and political leaders about the benefits of measles eradication.