Uploaded January 2021 | Updated September 2026, 1 hour ago

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In this video Olivia Swarthout clears up the confusion between 95% effectiveness and efficacy for Pfizer’s COVID-19 vaccine. She explains the mathematics of calculating vaccine efficacy and the difference between efficacy and effectiveness for the COVID-19 vaccine.

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Video Link: youtu.be/53ZjQWNfBcI

Chapters
0:00 COVID-19 95% Efficacy
0.39 Pfizer 95% Efficacy
1:06 What is a placebo?
1:45 Calculating Risk Percentage
3:15 Calculating 95% Efficacy
4:15 Scaling for US Population
5:05 Efficacy vs Effectiveness
7:45 Don't Forget