Figure 1. Inclusion Criteria for a Case-Control Study of Association Between 3 Doses of COVID-19 mRNA Vaccine and Symptomatic SARS-CoV-2 Infection Caused by the Omicron or Delta Variants.

Nucleic acid amplification tests (NAATs) were from the Increasing Community Access to Testing platform. EUA indicates Emergency Use Authorization.

^aNine tests were removed because of reported ages older than 100 years.

^bOf all tests with positive results, 17 620 were randomly selected for whole-genome sequencing and used to perform internal validation of S-gene target failure as a marker for the Omicron variant (eTable 1 in the Supplement). This included 4905 tests also included in the main case-control analysis.

^cDuring online registration for SARS-CoV-2 testing, individuals self-reported their COVID-19 vaccination status, including the number of doses (up to 4), product, and month and year of receipt for each dose. Vaccination data were considered incomplete if the number of doses reported did not match the products and dates reported.

^dThese 17 177 samples were used for the main case-control analysis that compared vaccination status between Omicron and Delta cases and SARS-CoV-2–negative controls. This included 2048 tests also included in the internal validation of S-gene target failure as a marker for the Omicron variant.

^eFor vaccine products, individuals could select from 4 options: Johnson & Johnson/Janssen, Pfizer-BioNTech, Moderna, and “other.”

^fPersons were considered eligible for a booster if they reported 2 doses, with a testing date 6 months or more after the second dose, or if they reported 3 doses, with the third dose 6 months or more after the second dose.

^gThese 52 978 samples were used for the main case-control analysis that compared vaccination status between Omicron and Delta cases and SARS-CoV-2–negative controls. This included 2857 tests also included in the internal validation of S-gene target failure as a marker for the Omicron variant.