..
— simonthong aka kitty poo (@KittyPo80176717) July 18, 2022
https://www.nejm.org/doi/10.1056/NEJMc2202542
..
1/
— Miguel Hernán (@_MiguelHernan) July 18, 2022
We estimated the effectiveness of a 4th dose of #COVID19 vaccine using observational data.
Compared with 3 doses, short-term effectiveness was
68% for hospitalization, 74% for death in persons aged 60+https://t.co/tKmFgKDAqp
And then we received an interesting criticism…
3/
— Miguel Hernán (@_MiguelHernan) July 18, 2022
What a wonderful opportunity to highlight the advantages of #TargetTrial emulation using observational data.
Note the analysis of randomized trials of vaccines is NOT restricted to people who get infected during the study.
Why should the analysis of observational studies be?
5/
— Miguel Hernán (@_MiguelHernan) July 18, 2022
Second, restricting the analysis to infected persons introduces selection bias if infection is a #collider.
And infection is likely to be a collider,
as #JacobWaxman, @OriMagen89, and I explain in our replyhttps://t.co/h57DYECIsB
The causal diagram would look like this 👇 pic.twitter.com/SbaUimuYn6
7/
— Miguel Hernán (@_MiguelHernan) July 18, 2022
If you are looking for a gentle introduction to #causaldiagrams, #selectionbias, and colliders
take a look at thishttps://t.co/mM4DTNtbDh
Once this is absent and risk of acquiring infection becomes very similar, helpful to know what will then happen to risk of severe disease, when the difference between groups will only be what happens after you've been infected
— Alasdair Munro (@apsmunro) July 18, 2022
2/
Identifying the direct effect of the vaccine that is not mediated by infection can be achieved
— Miguel Hernán (@_MiguelHernan) July 18, 2022
if infection (the mediator) is randomly assigned, or
if we adjust for confounders for the effect of infection,
not simply by CONDITIONING on the mediator
2/https://t.co/3qKpcvCfVx
Only 30 days of follow-up? 😲
— Frederik Feys (@FFeys) July 18, 2022
🤣"Safe and effective" It's all a paradise in papers paid by investors. But in "real world"… pic.twitter.com/kbIOQIHTOL
— M.A.C (@manuelcl10) July 18, 2022
..
Pingback: The effectiveness of a 4th dose mRNA vaccine | weehingthong