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> Simple math: if Pfizer says their vaccine is 90% effective at preventing severe disease then 10% of people are at risk of getting severe disease. That’s not
by nickles 5y ago
> Simple math: if Pfizer says their vaccine is 90% effective at preventing severe disease then 10% of people are at risk of getting severe disease.
That’s not quite how vaccine efficacy works. Suppose the risk of getting sick is 0.5% per thousand person hours when unvaccinated. A 90% vaccine efficacy means that the risk of getting sick is reduced to 0.05% per thousand person hours, not that 10% of people who get vaccinated are still vulnerable.
- syntaxing 5y agoI think you’re mixing effectiveness and efficacy. You’re both correct but talking about different terms minus that the parent comment needs some prior adjustment in the numbers to get the posterior.
- nickles 5y agoAccording to the WHO, efficacy refers to vaccine performance in controlled studies whereas effectiveness refers to performance in the broader population [0]. Data aggregated by JHU appears more or less consistent with estimates of vaccine efficacy [1]. [0] https://www.who.int/news-room/feature-stories/detail/vaccine-efficacy-effectiveness-and-protection https://www.who.int/news-room/feature-stories/detail/vaccine... [1] https://coronavirus.jhu.edu/pandemic-data-initiative/data-outlook/the-state-of-state-level-breakthrough-case-reporting https://coronavirus.jhu.edu/pandemic-data-initiative/data-ou...