Academic journal article Bulletin of the World Health Organization

Measles Control in Developing and Developed Countries: The Case for a Two-Dose Policy

Academic journal article Bulletin of the World Health Organization

Measles Control in Developing and Developed Countries: The Case for a Two-Dose Policy

Article excerpt

Introduction

Measles continues to be a serious public health problem in developing as well as developed countries, despite the availability of an excellent vaccine. The disease causes an estimated 1.4 million deaths annually, primarily in developing countries, but also occurs in outbreaks in developed countries, even where there is a well-established immunization programme.[1-6] Full control of the disease has not been achieved, in part because of the difficulty in reaching the needed coverage of infant populations to achieve the necessary levels of herd immunity even in developed countries, and because of problems of both primary and secondary vaccine failure.[7-31] As a result, views have been proposed that measles cannot be eradicated, without application of the lessons learned in the developed countries to developing countries.[4-7]

Current estimates of the coverage needed for fully protective herd immunity are 94-97%.[4] This level is very difficult to reach with 15-month-old infants even in the most developed countries, but it may be more readily achievable with school-age children through compulsory vaccination. In addition, there is the problem of vaccine failure, particularly when the vaccine is administered before the optimal time. Primary vaccination failure occurs at rates of 4-8%, and secondary failure at about 4%.[4, 22] Also, large numbers of cases occur among apparently appropriately vaccinated persons during epidemics, particularly in group settings such as schools, universities or sporting events. Many countries have experienced an upward shift in the age group of measles cases to those who may have been immunized before 1980 either too early, or with less stable vaccine preparations. Therefore, even 95% vaccination coverage of children up to 2 years of age is insufficient to fully control or eliminate this disease. In order to deal with these limitations, some countries have adopted a two-dose policy: one dose in infancy and a booster, usually at school age. All the available evidence suggests that two doses are justified and indicated in both developed and developing countries to achieve control of this disease.

Recent measles experience in a number of developed and developing countries is reviewed here, including recent literature on vaccine efficacy, as well as cost-benefit studies. The weight of evidence favours universal adoption of the two-dose schedule to achieve maximum feasible control of this vaccine-preventable disease.

Materials and methods

Measles incidence data were examined as reported to the WHO European Regional Office, the Centers for Disease Control in Atlanta (USA), the Laboratory for Disease Control in Ottawa (Canada), the Government Health Services in Judea/Samaria (West Bank) and Gaza, and the Department of Epidemiology of the Ministry of Health of Israel. We also examined published data for the Ministries of Health of the Philippines, Nigeria, and Malawi, and data assembled by UNICEF on population, mortality and immunization coverage.[5]

Findings

Developed countries

United States of America. In 1988 the population was 245.4 million, with a GNP per capita of US$ 19 840 and an infant mortality rate of 11/1000. Measles vaccination coverage of one-year-olds was reported as 96% in 1981, 82% in 1987/88, and 98% in 1988/89;[5] all states have mandatory immunization requirements for school entry, school attendance being virtually universal.

Measles was present in all parts of the USA prior to the introduction and widespread use of the vaccine. Between 1950 and 1959 the annual average of reported cases was 500 000, estimated to be 10% of the actual total, with 500 deaths per year.[4] Dramatic reductions (97-98%) occurred in measles incidence, from rates of 400-600 per 100000 in the pre-vaccination period (prior to 1963) to under 5 per 100 000 in the 1981-85 period, but epidemics are continuing among both immunized and unimmunized populations well into the 1990s. …

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