We have just put up uploaded a pre-print (https://www.medrxiv.org/content/10.1101/2021.07.19.21260759v1) that describes the derivation and validation of a prognostic model for Covid-19 severity in a cohort of undifferentiated adults at the time of diagnosis.
In Iceland, all individuals who were SARS-CoV-2-positive were prospectively enrolled into a telehealth service at a median of <24 hours from their positive test. We derived a prognostic model using data collected during the enrollment interview of 1,625 persons in the first-wave of infections and then later validated on the 3,131 individuals who were diagnosed during the second and third waves. We found (what we consider) excellent discrimination and validation. We also performed decision curve analysis and provided a case-study on how we suggest the model could (should?) be used.
Almost immediately after we finished our manuscript and uploaded to medrxiv, another wave of infections began in Iceland. The difference is that now, roughly 90% of Icelanders 16 years of age and older have been vaccinated . As we describe in our paper, we will use the prognostic model to decide who to enroll into the telehealth service using a cut-off of predictive risk that weighs the risks omitting enrollment with the benefits of not overwhelming the telehealth service. We have provided a interactive calculator that is built upon our prognostic model for this purpose (Prognostic model for COVID-19). However, we would like to display a rough estimate of the calculated risks given that the individual is vaccinated.
Given that an unvaccinated individual has a predicted risk of hospitalization xunvaccinated and given that we find a publication of a randomized controlled trial that that describes the odds ratio of hospitalization of vaccinated SARS-CoV-2 infected individuals compared to unvaccinated SARS-CoV-2 infected individuals, ORvac/unvac, how would we approximate xvaccinated? Could anyone point me to papers or textbooks that describe this kind of adjustment. Is my understanding correct that odds ratios would be the only transportable effect size? Given that the calculator strongly warns that xvaccinated is approximated and provides a citation for the odds ratio, are there any obvious reasons why this would be a poor idea?
P.S. Any and all critique of the prognostic model, its presentation and the manuscript is very well appreciated. It is currently undergoing peer review but I am a strong believer in open review. We tried to be as transparent as possible and followed the TRIPOD guidelines. All statistical code along with all the code output is available at OSF | Development and validation of a prognostic model for COVID-19: a population-based cohort study in Iceland