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Estimating vaccine efficacy over time after a randomized study is unblinded.
Anastasios A Tsiatis1, Marie Davidian1
1Department of Statistics, North Carolina State University, Raleigh, NC, USA.
Biometrics
|June 26, 2021
Summary
This study addresses waning vaccine efficacy (VE) for COVID-19 vaccines. It proposes a statistical framework to accurately measure VE over time, even with participant crossover in trials.
Area of Science:
- Immunology
- Epidemiology
- Biostatistics
Background:
- The COVID-19 pandemic spurred rapid vaccine development, with mRNA vaccines showing high initial efficacy.
- Concerns exist regarding the long-term durability of vaccine efficacy (VE) as trials continue.
- Participant unblinding and crossover in vaccine trials complicate the assessment of waning VE.
Purpose of the Study:
- To develop a statistical framework for inferring potential waning VE over time.
- To estimate VE at any postvaccination time point, accounting for trial complexities.
- To clarify assumptions regarding individual and population phenomena influencing VE.
Main Methods:
- Utilized a potential outcomes formulation to model VE.
- Developed methods for inference on waning VE within the Moderna trial's context.
- Addressed differential crossover of subjects based on infection risk.
Main Results:
- The proposed framework allows for robust inference on waning VE.
- Enables estimation of VE at specific time points post-vaccination.
- Clarifies assumptions and accounts for complexities in real-world trial data.
Conclusions:
- The statistical framework provides a method to accurately assess waning vaccine efficacy.
- It is adaptable to various vaccine trial designs and complexities.
- Crucial for understanding long-term vaccine performance against SARS-CoV-2.
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