1. Rabies

Reproductive number of rabies among dogs in Kenya is 2.44

Ro = 2.44

Generate sequence of numbers for fraction of population vaccinated from 0 to 1 with 0.1 interval.

fraction_vaccinated = seq (0, 1, 0.1)

Print fraction of population vaccinated.

cat ("Fraction of population vaccinated: ", fraction_vaccinated)
## Fraction of population vaccinated:  0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Compute effective reproductive number

Re = Ro * (1 - fraction_vaccinated)

Print effective reproductive number.

cat ("Effective reproductive number:", Re)
## Effective reproductive number: 2.44 2.196 1.952 1.708 1.464 1.22 0.976 0.732 0.488 0.244 0

Compute herd immunity threshold.

herd_immunity_threshold = 1 - (1/Ro)

Print herd immunity threshold.

cat ("herd immunity threshold = ", herd_immunity_threshold)
## herd immunity threshold =  0.5901639

Plot fraction of population vaccinated (versus) effective reproductive number.

subtitle = paste("Ro = ", Ro, ", Herd Immunity Threshold = ", round(herd_immunity_threshold, digits = 4) , sep="")

plot (fraction_vaccinated, Re, main = "Rabies", sub = subtitle, xlab = "Fraction of population vaccinated", ylab = "Effective reproductive number (Re)")

Results and Discussion

Reproductive number of rabies among dogs in Kenya is 2.44 (Kitala et al, 2002). The graph illustrates that as fraction of population vaccinated increases, effective reproductive number decreases. Herd immunity threshold is 59.02%; that is, at this level of vaccination coverage, effective reproductive number is 1 (Re = 1). When vaccination coverage is above 59.02%, effective reproductive number is less than 1 (Re < 1); thereby, rabies will be eliminated at these higher levels of vaccination coverage.

Public health implications

Recommend rabies vaccination among dogs in Kenya at coverage levels of above 59.02%.