*refers to the end of the person-time included in the analysis for each participant. The person-time ended on: 1) the day of the first infection, 2) the day of receipt of a third vaccine dose, 3) the day of receipt of a second vaccine dose if the interval between first and second dose is shorter than the manufacturer recommendation, 4) the day of the last weekly questionnaire before complete loss to follow-up, withdrawal or censor date, or the last weekly questionnaire before 1 Dec 2021.
**chronic conditions include: cancer, chronic heart disease, high blood pressure/hypertension, chronic kidney disease, chronic liver disease (such as cirrhosis, hepatitis, fatty liver disease), chronic lung disease (such as asthma, COPD), diabetes, immunocompromised (including solid organ transplant and HIV), neurologic disease (including cerebrovascular disease, epilepsy, multiple sclerosis), obesity, autoimmune disorder