Abbreviation: RT-PCR, reverse transcription polymerase chain reaction.

^aFisher exact test, Kruskal-Wallis rank sum test, and Pearson χ² test were used to calculate P values.

^bParticipants who identified as non-Hispanic American Indian, Alaska Native, Asian, and Native Hawaiian/Pacific Islander.

^cChronic conditions for CASCADIA and CoVE included asthma, heart disease, sleep apnea, Down syndrome, diabetes, cancer, autoimmune disease, liver disease, kidney disease, hematologic disease, neurologic or neuromuscular disease, stroke, deep vein thrombosis or pulmonary embolism, anxiety, depression, immunosuppression, hypertension, and thyroid disease. For VIEW: asthma, chronic pulmonary disease, obesity, heart disease, diabetes, liver disease, kidney disease, cancer, arthritis, hematologic disease, neurologic or neuromuscular disease, stroke, deep vein thrombosis or pulmonary embolism, anxiety, depression, immunosuppression, hypertension, and thyroid disease.

^dSixteen participants had missing data on the number of individuals in their household.

^ePrior infection was defined as laboratory-confirmed infection by RT-PCR from a study-collected specimen, positive anti-nucleocapsid SARS-CoV-2 antibody, or self-report of infection prior to enrollment or 1 September 2022.

^fTime since prior infection was calculated as the date of the prior infection to the first week that each participant was included in the analysis.

^gSymptomatic COVID-19 was defined as a positive RT-PCR test result and at least 2 COVID-19–like illness symptoms reported within 7 days of the specimen collection date.