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  1. 1
    Peer Reviewed

    Two-dose measles vaccination schedules.

    Rosenthal SR; Clements CJ


    Worldwide coverage of measles vaccine is about 80%, but many communities and countries have considerably lower coverage rates. WHO is concerned about measles occurring in infants between 6 and 12 months old, especially in densely populated African cities. Measles rarely occurs in infants under 6 months old, but the measles case fatality rate is greatest in the 1st year of life. WHO aims for an effective measles vaccine to be administered at 6 months old. A high titer vaccine appears to reduce survival among children receiving it. Some countries have reduced measles incidence by as much as 90% by achieving coverage levels greater than 90% with a single dose measles vaccine. Another method to prevent early measles cases and later vaccine failures is administration of the 1st dose around 6 months and a 2nd dose no earlier than 12 months. Measles vaccine policy in the US and some countries in Europe is routine 2-dose measles schedules: 1st dose between 12-19 months and 2nd dose at school entry. This schedule is appropriate in developed countries with good immunization coverage. Other countries schedule the 1st dose anywhere between 6-9 months and the 2nd dose between 12 months and 7 years. All mathematical models of the effects of 2-dose schedules indicate that 2-dose schedule are a great benefit. The literature shows that developing countries with high immunization coverage and well-managed immunization programs can effectively execute and sustain 2-dose measles schedules. Measles vaccination early in life sometimes results in a blunted antibody response. The 2-dose schedules are probably more expensive than 1-dose schedules and require more cold storage space. No field trials have looked at clinical efficacy of 2-dose measles schedules in developing countries. Ideal field trials would be randomized controlled trials. Demonstration projects can evaluate operational issues, e.g., dropout rates, cost, and vaccine usage. Case control studies can address technical and epidemiological issues.
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  2. 2

    Global models, world futures, and public policy: a critique.

    United States. Congress. Office of Technology Assessment

    Washington, D.C., Office of Technology Assessment, 1982 Apr. 120 p. (OTA Report OTA-R-165)

    Global models, as tools of policy formulation, have been used to evaluate or promote alternative actions and programs that might bring about different or more favorable world futures. This report surveys the assumptions, findings, and recommendations of 5 major global modeling studies. It also considers the use of global models within the US government, such as the World Integrated Model (WIM) that is being used by the US Joint Chiefs of Staff. The report presents strategies that have been suggested for improving the quality and relevance of the Government's modeling capability. Of particular interest in this connection is the newly created White House "national indicators system." Appendixes provided detailed comparative analyses of the models' projections of population, agriculture, and energy trends. Global modeling studies have varied widely in their purposes, techniques, findings, and prescriptions. Specific quantitative results have differed, but the studies have generally identified the same problems and seem to have arrived at roughly similar qualitative conclusions about the present state of the world and its plausible futures. As a tool of analysis, global modeling is neutral, yet it can be designed or used inappropriately. Global modeling is used by a variety of organizations. Global models offer several methodological advantages over traditional techniques of long range analysis and policy development: longer time horizon; comprehensiveness; rigor and accessibility; logic; and flexiblity. Global models are subject to several limitations that can constrain their accuracy, reliability, and usefulness: methodological, theoretical; and data constraints. Frequently cited institutional barriers include: poor communication between modelers and potential model users; narrow specialization of interests and responsibilities; lack of understanding, confidence, or support for modeling among top level policymakers; and lack of interest in longterm global issues on the part of the US Federal agencies, US Congress, and the general public. Proposed initiatives for improving the government's modeling capabilities usually reflect 4 fundamental priorites: correct existing deficiencies; coordinate existing capabilities and activities; support technical improvements in the government's capability and the state of the art; and link foresight with policymaking. The 5 global modeling studies addressed in this report demonstrate at least 3 fundamentally different "predictive styles"--World 3 model and Global 2000 examine what might happen if current trends continued, while the Latin American and UN world models examine the goals that might be realized through broad changes in those trends, and the WIM examines the policies and action that might bring those changes about. The models also vary significantly in their more specific purposes, assumptions, and methodologies, but they do display a limited consensus about the nature of the world system and the identity of the problems facing it, as well as some of the steps that must be taken to address them. Discussion examines the areas of general agreement or disagreement that emerge from these 5 studies.
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