A public health risk assessment for yellow fever vaccination: a model exemplified by an outbreak in the state of São Paulo, Brazil.

Ana Freitas Ribeiro,Roberta Spinola,Renato Pereira De Souza,Marcio Port-Carvalho,Francisco Antonio Bezerra Coutinho,Ana Cecilia Costa França,Marcelo Nascimento Burattini,Eduardo Massad,Marcos Amaku,Luis Fernandez Lopez,Helena Keico Sato,Ciléa Tengan,Melissa Mascheretti,Mariza Pereira

doi:10.1590/0074-02760140345

Abstract

We propose a method to analyse the 2009 outbreak in the region of Botucatu in the state of São Paulo (SP), Brazil, when 28 yellow fever (YF) cases were confirmed, including 11 deaths. At the time of the outbreak, the Secretary of Health of the State of São Paulo vaccinated one million people, causing the death of five individuals, an unprecedented number of YF vaccine-induced fatalities. We apply a mathematical model described previously to optimise the proportion of people who should be vaccinated to minimise the total number of deaths. The model was used to calculate the optimum proportion that should be vaccinated in the remaining, vaccine-free regions of SP, considering the risk of vaccine-induced fatalities and the risk of YF outbreaks in these regions.

Highlights

We propose a method to analyse the 2009 outbreak in the region of Botucatu in the state of São Paulo (SP), Brazil, when 28 yellow fever (YF) cases were confirmed, including 11 deaths
We apply a mathematical model described previously to optimise the proportion of people who should be vaccinated to minimise the total number of deaths
Yellow fever (YF) is an haemorrhagic fever caused by the prototype member of the genus Flavivirus family Flaviridae (Monath 2001, Moreno et al 2011)

Summary

Introduction

We propose a method to analyse the 2009 outbreak in the region of Botucatu in the state of São Paulo (SP), Brazil, when 28 yellow fever (YF) cases were confirmed, including 11 deaths. Genomic sequence analysis suggests that the YF virus evolved from other mosquito-borne viruses 3,000 years ago (Zanotto et al 1996) It is an infection endemic in the tropical forests of Africa and Central and South America (Barnett 2004). During occupational or recreational activities in forest areas, susceptible individuals are bitten by mosquitoes carrying the YF virus and develop the clinical disease with varying degrees of severity These individuals may eventually return infected to their home cities, which is of particular concern in urban regions infested by Aedes aegypti (YF vector of the urban cycle of the disease), the same transmitter of dengue fever and the mosquito responsible for huge YF outbreaks in urban centres in the past.

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