a common refrain of preprint papers is that they "haven't undergone peer review"
medRxiv
Effectiveness of the Influenza Vaccine During the 2024-2025 Respiratory Viral Season: A Prospective Cohort Study
Background The purpose of this study was to evaluate the effectiveness of the influenza vaccine during the 2024-2025 respiratory viral season.
Met...
this is a reminder to anyone who can read and understand scientific publications "WE ARE THE PEER REVIEW"
here is my review of this paper:
This prospective cohort study evaluates the effectiveness of the 2024-2025 influenza vaccine among 53,402 employees of the Cleveland Clinic Health System. Using a time-dependent covariate Cox proportional hazards model, the authors report that they were unable to identify a protective effect of the vaccine.
There is a strong likelihood that the results are driven by unmeasured residual confounding, specifically differential healthcare-seeking behavior and detection bias.
Ther defense against this bias (Figure 2 analysis) is not great. The authors admit in the results (are driven by vaccinated individuals being significantly more likely to undergo PCR testing than unvaccinated individuals.
They argue that because the test positivity rate was similar between groups (Figure 2), the higher case count involves true infection rather than PCR test seeking behavior.
If the vaccine has low or null effectiveness and the vaccinated population is tested at a rate 1.5x or 2x higher than the unvaccinated population, the observed incidence rate will be higher in the vaccinated group simply due to increased case ascertainment. A similar test positivity rate across groups, combined with higher testing volume in one group, means we would expect to find more cases in the high-testing group.
The study is really just measuring the "incidence of detected influenza," which appears to be a function of testing and they were unable to adjust for "propensity to seek care."
It is not possible to associated increased cases of influenza with vaccination but there is no doubt from this data set that the influenza vaccine had little to zero protective effects. and therefore raises the requesting of are potential adverse effects worth it.
