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Time is of the essence: exploring a measles outbreak response vaccination in Niamey, Niger - PubMed

  • ️Tue Jan 01 2008

Time is of the essence: exploring a measles outbreak response vaccination in Niamey, Niger

R F Grais et al. J R Soc Interface. 2008.

Abstract

The current World Health Organization recommendations for response during measles epidemics focus on case management rather than outbreak response vaccination (ORV) campaigns, which may occur too late to impact morbidity and mortality and have a high cost per case prevented. Here, we explore the potential impact of an ORV campaign conducted during the 2003-2004 measles epidemic in Niamey, Niger. We measured the impact of this intervention and also the potential impact of alternative strategies. Using a unique geographical, epidemiologic and demographic dataset collected during the epidemic, we developed an individual-based simulation model. We estimate that a median of 7.6% [4.9-8.9] of cases were potentially averted as a result of the outbreak response, which vaccinated approximately 57% (84563 of an estimated 148600) of children in the target age range (6-59 months), 23 weeks after the epidemic started. We found that intervening early (up to 60 days after the start of the epidemic) and expanding the age range to all children aged 6 months to 15 years may lead to a much larger (up to 90%) reduction in the number of cases in a West African urban setting like Niamey. Our results suggest that intervening earlier even with lower target coverage (approx. 60%), but a wider age range, may be more effective than intervening later with high coverage (more than 90%) in similar settings. This has important implications for the implementation of reactive vaccination interventions as they can be highly effective if the response is fast with respect to the spread of the epidemic.

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Figures

Figure 1
Figure 1

Map of Niamey, Niger showing the three communes and quartiers.

Figure 2
Figure 2

Reported measles cases in Niamey, Niger (November 2003 to July 2004) by commune and the performance of the model by commune. The solid lines depict the median forecast epidemic curve over 1000 simulations including the vaccination intervention targeting 50% of children aged 6–59 months for each commune.

Figure 3
Figure 3

Simulation of epidemic with and without vaccination intervention. The number of reported measles cases per week is shown in the grey histogram. The blue line depicts the median forecast epidemic curve over 1000 simulations including the vaccination intervention targeting 50% of children aged 6–59 months. The red line shows the median of 1000 simulations of the forecast epidemic curve without any intervention.

Figure 4
Figure 4

Estimated proportion of cases averted with a vaccination intervention targeting children aged between 6 and 59 months for a vaccination intervention lasting 10 days. The blue line shows an intervention at 60 days, the red line an intervention at 90 days and the green line an intervention at 120 days.

Figure 5
Figure 5

Estimated proportion of cases averted with a vaccination intervention targeting children aged 6 months to 15 years for a vaccination intervention lasting 10 days. The blue line shows an intervention at 60 days, the red line an intervention at 90 days and the green line an intervention at 120 days.

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