Table 2.

PCR test results among study participants with at least three BNT162b2 vaccine doses at different time points, between 10 January and 13 March 2022, and adjusted relative vaccine effectiveness against SARS-CoV-2 infection for participants receiving a fourth dose

Time after receiving fourth dose	Matched analysis*				Multiple tests analysis†
	Positive PCR	Negative PCR	Adjusted rVE (%; 95% CI)		Positive PCR	Negative PCR	Adjusted rVE (%; 95% CI)
Received only three doses (reference)	19 211	25 861	—		22 046	74 268	—
7-13 days	3263	11 376	57.7 (55.6 to 59.7)		3555	23 423	46 (43.7 to 48.3)
14-20 days	2131	6264	65.1 (63 to 67.1)		2439	19 478	61.7 (59.8 to 63.6)
21-27 days	1785	4972	64 (61.6 to 66.3)		2033	17 484	63.9 (62 to 65.8)
28-34 days	1416	3716	58.1 (54.8 to 61.1)		1613	15 274	61 (58.6 to 63.2)
35-41 days	930	2569	55 (50.6 to 58.9)		1084	12 664	58.8 (55.7 to 61.6)
42-48 days	684	1940	50.2 (44.5 to 55.3)		796	11 146	57.1 (53.4 to 60.5)
49-55 days	556	1501	42.5 (35.1 to 49.1)		654	9719	52.8 (48.2 to 57)
56-62 days	542	1364	33.4 (23.8 to 41.8)		625	8214	42.6 (36.6 to 48.1)
63-69 days	213	491	22 (4.9 to 36.1)		256	2662	29.5 (18.1 to 39.2)
Overall	30 731	60 054	—		35 101	194 332	—

PCR=polymerase chain reaction; rVE=relative vaccine effectiveness (calculated as 100%×(1−odds ratio) for each week since vaccination).

^*Matched analysis used 1:m matching, with up to five controls per case, based on seven factors: sex, age group, city of residence, socioeconomic status, calendar week of first test, month of receipt of the third dose, and a categorical variable for the living environment (a medical nursing home, assisted living facility, or private residence). Analysis also adjusted for underlying comorbidities and previous test-taking behaviour.

^†Odds ratios were adjusted for comorbidities, age group, nursing home or assisted living residence, previous test-taking behaviour, biological sex, calendar week of testing, residential socioeconomic status, and month of receipt of the third dose