The scientific evidence shows that COVID-19 vaccination reduces the risk of infection and mortality; analysis of cases and deaths from 145 countries is methodologically flawed
Ecological studies compare aggregate data from whole groups or populations and seek correlations between exposure to a potential risk factor and the frequency of disease. They are relatively quick and inexpensive to do compared to studies such as randomized controlled trials. However, there are also important pitfalls to ecological studies. For example, it’s difficult to account for confounding factors in the study, which are variables that affect the outcome of an experiment, but aren’t the variables being studied in the experiment. As such, it is challenging to draw causal inferences solely from an ecological study.