JAMAevidence JAMA Guide to Statistics and Methods Test-Negative Study Designs for Evaluating Vaccine Effectiveness With Dr Dean
Apr 2, 2026
Natalie Exner Dean, PhD, associate professor of biostatistics and bioinformatics at Emory, studies infectious disease and vaccine effectiveness. She explains enrolling symptomatic people, using test-positives versus test-negatives to estimate effectiveness. She covers calculating effectiveness from odds ratios, key assumptions about disease specificity, bias reduction via healthcare-seeking restrictions, and limits from test performance and misclassification.
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Why PostApproval Studies Are Essential
- Vaccines undergo large randomized phase 3 trials for approval but require observational studies after licensure to assess real-world performance.
- Natalie Exner Dean highlights evolving factors like new strains, boosters, and real-world effectiveness as drivers for post-approval studies.
How The TestNegative Design Works
- The test-negative design enrolls people with a clinical syndrome who seek testing and classifies those testing positive as cases and those testing negative as controls.
- Natalie Exner Dean notes this built-in control group simplifies measuring vaccine effectiveness using routine testing encounters.
Calculating Vaccine Effectiveness
- Vaccine effectiveness is estimated as 1 minus the adjusted odds ratio comparing vaccination among test-positive cases versus test-negative controls.
- Dean explains that when vaccines work well, vaccinated fraction is lower among cases than controls.