<prompt> True about OPT ail except:We get quick immune responseIt is a live vaccineIt is used in epidemicMaternal antibody interferes with immune response  <response>: Ans. a. Disease in very fatal and or easily curable Prevalence P: Incidence I x Duration D Q Incidence reflects causal factorsdeg Duration reflects the prognostic factorsdeg If the prevalence is very low, then either incidence is low or duration is shodeg . Duration is sho if the disease is easily curable or very fatal 