Vaccine efficacy/effectiveness: Calculation, visualization, and interpretation based on an exemplary systematic review on COVID-19 vaccination in children

Date & Time
Tuesday, September 5, 2023, 2:00 PM - 3:30 PM
Location Name
Session Type
Workshop - training
Statistical methods
Target audience
Authors and users of systematic reviews on vaccination effects
Level of difficulty

Background: Vaccine efficacy/effectiveness (VE) is commonly used to express the effect of vaccines to prevent diseases, e.g., COVID-19. Although the general formula for VE calculation is straight forward on the first glance [VE=(1-VE_ratio)*100], one has to take into account that several different VE-ratio measures are used in individual studies, which are potentially included in systematic reviews and meta-analyses. These include, for example, risk ratios, odds ratios, hazard ratios, or incidence rate ratios. This cannot only lead to questions in VE calculation but also in issues regarding interpretation of a pooled estimate of different VE ratios. Moreover, visualization of VE estimates in forest plots is not yet possible in RevMan Web resulting in the need for alternative approaches, e.g., using the software R.
Objectives: To explain, discuss, and interpret VE calculation, VE meta-analysis, and VE visualization in forest plots based on an exemplary systematic review on COVID-19 vaccination in children.
Description: In this workshop, we would like to address all participants interested in deeper insights in VE methodology and meta-analyses of VE outcomes (e.g., SARS-CoV-2 infection, hospitalisation). Previous knowledge on VE and statistics is advantageous, but not required. We will start with a short introduction on VE calculation. In group exercises, participants will calculate, interpret, present, and discuss VE for different outcomes and study designs. We will illustrate the clinical relevance by comparing VE with a calculated corresponding absolute effect for selected outcomes. Further, we will present different ways of VE visualization based on forest plots from different published examples, which we will discuss interactively with the workshop participants. We will demonstrate how to calculate and produce a VE forest plot in R, including subgroup and sensitivity analyses using simple, user-friendly R code from package ‘meta’, which has been implemented recently. The code will be made available to all participants after the workshop. After completing the workshop, participants will have a solid understanding of VE calculation, visualization, and interpretation, which will be useful for an enhanced understanding and for conducting systematic reviews on vaccination effects.

Schwarzer G1
1Institute of Medical Biometry and Statistics, Faculty of Medicine and Medical Center, University of Freiburg, Germany