Case-Fatality Rate (CFR) is based on the case investigations and the total number of confirmed cases. If possible, estimate it by age-group.
CFR = No. of patients who died of a specific VPD/Total No. of cases of the same VPD X 100
Vaccine efficacy (VE) is the ability of the vaccine to prevent disease effectively and is affected by the age at immunization, potency of the vaccine (quality of cold chain) and overall immunization coverage.
VE = (Attack Rate among unvaccinated (ARU) -Attack Rate among Vaccinated (ARV)
(Attack Rate among unvaccinated (ARU)
Attack Rate is an incidence rate (usually expressed as a percent), used only when the
population is exposed to a VPD for a limited period of time, such as during an outbreak. It is
calculated as follows:
AR= Number of new cases of a VPD during a specified time interval X 100
Total population at risk during the same interval
