COVID-19 Vaccination: Early Estimates of a Relative Post Interventional Case Fatality Risk

Background: Recent epidemiological studies have demonstrated the efficacy of vaccines in reducing COVID-19 absolute case-fatality risks (CFRs) on a real-world global scale. However, these studies used cumulative (add-on) deaths and case accounts as nominators and denominators respectively.

This study aims to shed light on the relative post-COVID-19 vaccination non– cumulative CFR as a tool in monitoring the effectiveness of this intervention.

Methodology: We used post-vaccination non- cumulative counts of deaths and cases as at April 3, 2021, for a comparison of pre-COVID-19 vaccination data.

Sixteen countries/territories, which ran the COVID-19 vaccination program for at least a hundred days, were included in the study.

A matched paired t-test and a receiver operating characteristic (ROC) test were used for statistical analyses.

Results: The relative post-COVID-19 vaccination CFRs are less than absolute (cumulative) CFRs and less than pre-vaccination CFRs. The matched paired t-test for testing mean differences between pre-COVID-19 vaccination and relative post-COVID-19 vaccination CFRs show a p-value level of (0.126).

The ROC test shows that the area under the curve was 0.391 for relative post-COVID-19 CFRs with an asymptotic significance of 0.291. The best COVID-19 cut-off CFR point was 1.6% which is an observed discriminator level between pre-vaccinated high CFRs and relative post-vaccinated CFRs lower level.

Conclusions: The relative post-COVID-19-vaccination CFR is more sensitive than absolute CFR and can be used as a tool for measuring the effectiveness of COVID-19 vaccination coverage in reducing CFR in addition to standered parameters.

Recommendations: The real world relative post-interventional CFR can be used as new indicator to replace absolute (cumulative) post-interventional CFR) as an early pos- interventional assessment.