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The impact of immunization control activities on measles outbreaks in middle and low income countries - PubMed

Review

The impact of immunization control activities on measles outbreaks in middle and low income countries

R B Aylward et al. Int J Epidemiol. 1997 Jun.

Abstract

Background: The World Health Organization recommended strategy for responding to measles outbreaks in developing countries does not promote the use of immunization campaigns due to their high cost, disruptive nature and limited impact. Given the substantial morbidity and mortality associated with such outbreaks, a literature review was conducted as a basis for re-evaluating this policy.

Methods: Reports of supplementary immunization activities that were performed to control measles outbreaks in middle or low income countries were identified. The impact of the immunization activities on the course of each outbreak was evaluated by examining the data provided.

Results: Of 66 reports detailing a measles outbreak in a middle or low income country, 17 described supplementary immunization activities which included seven 'non-selective' immunization campaigns, three 'selective' campaigns and one use of an early 2-dose schedule. Eight of the reports commented on the impact of the response, five of which reported a reduction in outbreak morbidity. Only one of the reports, from an isolated island outbreak, provided sufficient data to support a possible reduction in outbreak-associated morbidity.

Conclusions: There are limited data on the impact of measles outbreak immunization activities from developing countries. The available data do not support a change in the WHO recommended strategy for conducting a limited, if any, immunization response to such outbreaks. Immunization strategies which aim to prevent outbreaks may be more effective than campaigns to interrupt transmission of an outbreak which has already begun.

PIP: Because of their high cost, disruptive nature, and limited impact, immunization campaigns are not recommended by the World Health Organization (WHO) in response to measles outbreaks in developing countries. The authors reviewed the available literature to assess whether that WHO policy should stand or be changed. 66 reports were identified detailing a measles outbreak in middle- or low-income countries. 17 of those reports described supplementary immunization activities to control measles outbreaks which included seven nonselective immunization campaigns, three selective campaigns, and one use of an early two-dose schedule. Eight reports commented upon the impact of the intervention, five of which reported a reduction in outbreak morbidity. Only one report, from an isolated island outbreak, provided sufficient data to support a possible reduction in outbreak-associated morbidity. The available data therefore do not support a change in the WHO-recommended strategy. Immunization strategies to prevent outbreaks may be more effective than campaigns to interrupt transmission of an outbreak which has already begun.

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