Alliance for Pandemic Preparedness

March 1, 2021

Interpreting Vaccine Efficacy Trial Results for Infection and Transmission

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  • [Pre-print, not peer-reviewed] In simulations of randomized trials to estimate the effect of vaccination on transmission, one dose of the Moderna vaccine reduced the potential for transmission by at least 61%.  The analysis suggested that the impact of a given vaccine on viral positivity should be assessed separately in symptomatic individuals and positive test results obtained cross-sectionally, regardless of symptoms. The approach also suggested that the odds ratio of carriage for vaccine vs. placebo can provide an unbiased estimate of vaccine effectiveness against viral positivity, under certain assumptions, and provide a lower bound for transmissibility. 

Lipsitch and Kahn. (Feb 28, 2021). Interpreting Vaccine Efficacy Trial Results for Infection and Transmission. Pre-print downloaded Mar 1 from https://doi.org/10.1101/2021.02.25.21252415