Table 2. Symptom duration among participants reporting symptoms by variant wave in study of COVID-19 infection, North Carolina, USA*.

Variant period	Beta (95% CI)†	p value	Marginal mean duration, d (95% CI)‡
Pre-Delta	NA	NA	9.7 (9.0–10.4)
Delta	−1.3 (−2.0 to −0.57)	<0.001	8.4 (7.8–9.1)
Omicron	−3.8 (−4.6 to −3.1)	<0.001	5.9 (5.3–6.4)

*Data are adjusted for age, vaccination status, boosting, reinfection, and sex. NA, not applicable. †Differences from reference wave (pre-Delta) in the linear model. ‡Marginal mean represents the estimated mean duration of a symptomatic period across all levels of age, vaccination status, boosting, reinfection, and sex.