Table 2.

Comparison of SARS-CoV-2 infection (PCR positive) at MCRDPI between the seropositive and seronegative groups

	Seropositive group (n=189)	Seronegative group (n=2247)	Proportion difference (95% CI), p value	Incidence rate ratio (95% CI), p value
PCR positive	19 (10%)	1079 (48%)	−38% (−45 to −31), p<0·001	..
Observed person year	17·1	175·2	..	..
Incidence rate per year	1·11	6·16	..	0·18 (0·11 to 0·28), p<0·001

The analysis is based on the 2436 participants who had valid PCR data obtained during the prospective follow-up period. MCRDPI=Marine Corps Recruit Depot—Parris Island.