3 ms·

I skimmed the article you linked to[1], but I still don't understand the advantage of using the absolute risk reduction rather than the relative risk reduction

I skimmed the article you linked to[1], but I still don't understand the advantage of using the absolute risk reduction rather than the relative risk reduction (or the point of reporting both). It seems it's like the same information expressed differently. I'm guessing that there must be an intuitive advantage like measuring the fuel economy of a car in gallons per 100 miles rather than the usual miles per gallon, but I'm not seeing it. Can you explain further? [1] Quoting the article's explanation of AAR vs RRR: "The vaccine and placebo groups in Figure 1 each have 100 randomly assigned individuals with no history of infection, and an event is defined as the incidence of infection among all individuals during the course of the trial. The percentage of events in the vaccine group is the experimental event rate (EER) or the risk of infection in the vaccine group (1/100 = 1%), and the percentage of events in the placebo group is the control event rate (CER) or the risk of infection in the placebo group (2/100 = 2%). Absolute risk reduction (ARR) is the disease risk difference between the placebo and vaccine groups, i.e., the CER minus the EER (2% − 1% = 1%). The ARR is also known as the vaccine disease preventable incidence (VDPI). Relative risk reduction (RRR) or vaccine efficacy (VE) is the reduced risk from vaccination, the ARR or VDPI, relative to or divided by the risk in unvaccinated individuals, the CER (1%/2% = 50%)".

smnrchrds 5y ago
I share your skepticism. Personally, I have talked to people (educated and intelligent people) who refuse to get the vaccine because "it is only ~1% effective". Using ARR seems to cause more confusion and misunderstanding that RRR.
vidoc 5y ago
> I'm guessing that there must be an intuitive advantage like measuring the fuel economy of a car in gallons per 100 miles rather than the usual miles per gallon, but I'm not seeing it. Can you explain further? Sure, ARR is more interesting for risk/cost benefits analysis. So much so that it is part of the official FDA guidelines expressed in this document ("Communicating risks and benefits: An evidence based user guide" [1]). "Another statistical choice is between reporting relative or absolute risks. Because there is no way to infer the latter from the former, absolute risks are always more informative. Doubling a risk means very different things if that entails going from 10% to 20% or from 0.001% to 0.002%.Even when they contain the same information, different summaries can highlight different perspectives, hence bias choices." Besides, if you compare the ranks of the main vaccines in each stat, you can see that it is not the same information expressed differently: ARR: AZ 1.3%, Moderna 1.2%, J&J 1.2%, 0.84% Pfizer RRR: 95% Pfizer, 94% Moderna, 67% J&J, 67% AZ 1: https://www.fda.gov/media/81597/download https://www.fda.gov/media/81597/download

smnrchrds 5y ago

I share your skepticism. Personally, I have talked to people (educated and intelligent people) who refuse to get the vaccine because "it is only ~1% effective". Using ARR seems to cause more confusion and misunderstanding that RRR.

vidoc 5y ago

> I'm guessing that there must be an intuitive advantage like measuring the fuel economy of a car in gallons per 100 miles rather than the usual miles per gallon, but I'm not seeing it. Can you explain further? Sure, ARR is more interesting for risk/cost benefits analysis. So much so that it is part of the official FDA guidelines expressed in this document ("Communicating risks and benefits: An evidence based user guide" [1]). "Another statistical choice is between reporting relative or absolute risks. Because there is no way to infer the latter from the former, absolute risks are always more informative. Doubling a risk means very different things if that entails going from 10% to 20% or from 0.001% to 0.002%.Even when they contain the same information, different summaries can highlight different perspectives, hence bias choices." Besides, if you compare the ranks of the main vaccines in each stat, you can see that it is not the same information expressed differently: ARR: AZ 1.3%, Moderna 1.2%, J&J 1.2%, 0.84% Pfizer RRR: 95% Pfizer, 94% Moderna, 67% J&J, 67% AZ 1: https://www.fda.gov/media/81597/download https://www.fda.gov/media/81597/download