Table 1.

Overview study characteristics of the included studies

Study characteristics	n (%)
Number of studies	14
Study design – prospective cohort study	14 (100%)
Region
Northern America	6 (42.9%)
Southern America	1 (7.1%)
Europe	1 (7.1%)
Middle East	1 (7.1%)
Asia	5 (35.7%)
Setting/population
Non-hospitalised SARS-CoV-2-positive persons	3 (21.4%)
Non-hospitalised SARS-CoV-2-positive health care workers	3 (21.4%)
SARS-CoV-2 positive university students and employees	2 (14.3%)
SARS-CoV-2 positive prisoners	1 (7.1%)
Primary cases in households	1 (7.1%)
Isolated or mandatorily hospitalised non-critically ill COVID-19 patients	3 (21.4%)
Hospitalised patients with mild to moderate COVID-19	1 (7.1%)
Sample size, range	6-93
Male, range	22–100%
Age
Mean age, range	22–42 y
Median age, range	22-67 y
Definition day zero for the viral culture serial sampling
Symptom onset	8 (57.1%)*
Diagnosis	2 (14.3%)
Symptom onset or diagnosis	4 (28.6%)
SARS-CoV-2 variant of concern
Pre-Delta	1 (7.1%)
Pre-Delta/Delta	3 (21.4%)
Delta	2 (14.3%)
Pre-Delta/Delta/Omicron	1 (7.1%)
Delta/Omicron	3 (21.4%)
Omicron	4 (28.6%)
Vaccination coverage in the study population, range	18–100%
COVID-19 vaccine
mRNA vaccine	1 (7.1%)
mRNA or vector vaccine	4 (28.6%)
mRNA or inactivated vaccine	1 (7.1%)
mRNA or vector or inactivated vaccine	2 (14.3%)
Vector or inactivated vaccine	1 (7.1%)
Not reported	5 (35.7%)
Risk of bias assessment
Low risk of bias	0 (0%)
Moderate risk of bias	12 (85.7%)
High risk of bias	2 (14.3%)

*One study reported data separately for ‘since symptom onset’ and ‘since diagnosis.’ To avoid duplicate data, we extracted only the ‘since symptom onset.’