Table 2.

Epidemiological parameters.

parametervalues per year unitremarks/sources
rbirths per year0.0127r = d2(d1 + f)/(d2 + f)
fmaturity rate1/19
d1juvenile death rate20/100 000US Census, CDC/NCHS
d2adult death rate1/55
ks,1juvenile death rate from varicella (no vaccine)1/100 000[3]
ks,2adult death rate from varicella (no vaccine)20/100 000
kv,1varicella mortality of vaccinated juveniles1/10 000 000[1]
kv,2varicella mortality of vaccinated adults20/10 000 000
σ1/duration of incubation period26[16]
δs1/duration of infectious period (no vaccine)52
δv1/duration of infectious period if vaccinated81[17]
β1transmission rate—juveniles to juveniles1760based on Ro = 9.4 and the probability (approx. 90%) of acquiring varicella by age 20 prior to the availability of vaccine
β2transmission rate—adults to adults, adults to juveniles and juveniles to adults250
vvaccination probability(variable of interest)