Background: The tension between science and ideology seems as old as science itself. To what extent is science used/misused to support certain ideologies? Does ideologies or purely material interests have any influence on the results of scientific research, and to what extent? Methods: Logically inconsistent scientific methods can contribute more to the formation of ideologies than to reliable scientific knowledge. In the long run, such methods open the doors wide for ideologies to be part of the formation of science and that science itself evolves backward into pure ideology. Results: The statistical method of calculating the vaccine efficacy has been re-evaluated. Conclusion: Mathematically, today's method of calculating the vaccine efficacy is logically not consistent.