Measles outbreak in a northern Pakistani village: epidemiology and vaccine effectiveness

Abstract

In the spring of 1990, local community health workers reported a measles outbreak in several partially vaccinated villages in the Punial Valley in northern Pakistan. The authors conducted an investigation in one of these villages to assess vaccine coverage and vaccine efficacy and to describe the patterns of measles outbreaks that prevailed in this community. The results of a survey of the entire village revealed two major gaps in vaccine coverage: the small minority Sunni community and children over 3 years of age. Vaccine efficacy was estimated to range from 73 to 90% but was markedly reduced in children who were vaccinated under 12 months of age. The occurrence of an outbreak in a community in which a relatively new vaccination program is primarily directed at younger children has been predicted by theoretical models of measles dynamics and is consistent with the experience of other vaccination programs in the developing world. These observations suggest that, in some areas of the developing world, the age groups targeted to receive measles vaccinations may need to be broadened to ensure adequate coverage to prevent recurrent outbreaks.

PIP: This report documents an investigation of a measles outbreak in Punial Valley, northern Pakistani village in which a vaccination program was well established. These villages had been receiving routine immunizations from the Expanded Program on Immunization administered by the Aga Khan Health Service, Pakistan. The authors conducted an investigation in one of these villages to assess vaccine coverage and vaccine efficacy and to describe the patterns of measles outbreak that prevailed in this community. Two major gaps in vaccine coverage were revealed in the survey: the small minority Sunni community, and children over 3 years of age. Vaccine efficacy was estimated to range from 73% to 90% but was significantly reduced in children who were vaccinated under 12 months of age. Theoretical models of measles dynamics have predicted the occurrence of an outbreak in a community in which a relatively new vaccination program is primarily directed at younger children. Such is also consistent with the experience of other vaccination programs in the developing world. These observations suggest that in some areas of the developing world, the scope of age coverage for measles vaccinations may need to be broadened to prevent recurrent outbreaks.