Sources of bias in observational studies of covid-19 vaccine effectiveness

In other words, 90%+ COVID "vaccine" efficacy claims are all bogus.

Discussion of multiple factors that can bias estimates of covid-19 vaccine effectiveness, such as:

1. vaccination status misclassification;

2. testing differences; and

3. disease risk factor confounding.

Our article complements these observations by providing examples based on actual data sets that quantify how case-counting window bias, age bias, and background infection rate bias can profoundly complicate the analysis of observational studies, shifting covid-19 vaccine effectiveness estimates by an absolute magnitude as high as 50% to 70%.

Daily covid-19 cases and vaccination rates—United States, UK, and Israel, 2021. Israel: At 20% “fully vaccinated,” daily case rate remained high (timepoint A). At 50%, daily case rate dropped to a seasonal low (timepoint B). UK and United States: Daily case rates dropped drastically with few “fully vaccinated” (timepoint A). At 20% and 5% “fully vaccinated,” daily case rates approached seasonal lows (timepoint B). Data source: OurWorldInData.

Sources of bias in observational studies of covid-19 vaccine effectiveness

Kaiser Fung MPhil, MBA, Mark Jones PhD, Peter Doshi PhD

First published: 26 March 2023