01.12.2018 | Research article | Ausgabe 1/2018 Open Access

# Estimating the number of unvaccinated Chinese workers against yellow fever in Angola

- Zeitschrift:
- BMC Infectious Diseases > Ausgabe 1/2018

## Electronic supplementary material

## Background

## Methods

_{1}is a scale parameter that determines the maximum incidence, c

_{2}is the age with the maximum incidence, c

_{3}represents the width of the time-dependent incidence function, and c

_{4}and. c

_{5}are fitting parameters with no physical meaning. The fitting accuracy can be observed in Fig. 1. From the Inc( t) function, we calculated, through the Ross-Macdonald SIR model, the local YF force of infection, λ( t) which is related to the risk of at least one infection, π( t), using the following equation [ 8]:

^{− 1}weeks

^{− 1}), a hosts’ life expectancy of 65 years (2.96*10

^{− 4}weeks

^{− 1}) and a lethality of yellow fever of 41% in 4 weeks (7.14*10

^{− 1}weeks

^{− 1}).

## Results

^{− 4}. The total number of cases retrieved by the model was 842 symptomatic cases among the Angolese populations and 10 symptomatic cases among the Chinese cohort, which is consistent with the actual numbers. To explain the observed 11 symptomatic cases among the Chinese foreign workers in Angola (which implies in 97 actual infections), we calculated that all the 259,000 Chinese must have been susceptible, that is, non-vaccinated. In other words, according to these calculations, none of the Chinese workers had received the YF vaccine. There may be different reasons for the absence of vaccination. For example, for one case there were medical contraindications with regards to yellow fever vaccination [ 11].