Ionnandis didn't adjust for infection-death lag (which has big impact in the exponential infection increase part of the curve); his California IFR study was very flawed and undisclosed funded by the founder of Jet Blue.
His early influential paper before that was way off and said IFR might be even lower, around the common cold.
Around 0.5%-1.5% IFR without overwhelmed hospitals was the common scientific consensus very early on and was more right. Some treatment methods like proning and demonstrated effectiveness of steroids in a certain schedule helped drop things a good bit a few months in, around 30% if I remember.
His early influential paper before that was way off and said IFR might be even lower, around the common cold.
Around 0.5%-1.5% IFR without overwhelmed hospitals was the common scientific consensus very early on and was more right. Some treatment methods like proning and demonstrated effectiveness of steroids in a certain schedule helped drop things a good bit a few months in, around 30% if I remember.