Is incidence proportion the same as attack rate in epidemiology?

Answer 1

Yes, this is correct:

Incidence proportion (or attack rate or risk)=Number of new cases of disease during specified time interval / Population at start of time interval

It is often confused with another measure of morbidity with the same numerator but different denominator:

Incidence rate (or person-time rate)=Number of new cases of disease during specified time interval / Summed person-years of observation or average population during time interval

https://www.cdc.gov/csels/dsepd/ss1978/lesson3/section2.html