Table 3. Adjusted Hazard of Breakthrough Infection by Month of Follow-up in Matched Cohorts of Vaccinated Individuals With vs Without Prior Infection.

Follow-up time, mo	Vaccinated with prior infectiona		Vaccinated with no prior infectiona		Absolute difference of cumulative incidence (95% CI)b	Adjusted hazard ratio (95% CI)c	P value
	No.	Cumulative incidence (95% CI)	No.	Cumulative incidence (95% CI)
BNT162b2
1	96 125	0.05 (0.03 to 0.06)	281 488	0.24 (0.23 to 0.26)	0.19 (0.16 to 0.22)	0.19 (0.14 to 0.26)	<.001
2	85 702	0.08 (0.07 to 0.10)	250 851	0.43 (0.41 to 0.46)	0.35 (0.32 to 0.38)	0.19 (0.13 to 0.27)	<.001
3	70 718	0.12 (0.10 to 0.14)	203 501	0.60 (0.57 to 0.63)	0.48 (0.45 to 0.51)	0.21 (0.14 to 0.31)	<.001
4	37 004	0.15 (0.12 to 0.18)	107 822	0.81 (0.78 to 0.85)	0.66 (0.62 to 0.70)	0.13 (0.08 to 0.22)	<.001
5	27 231	0.22 (0.18 to 0.27)	79 210	1.20 (1.15 to 1.26)	0.98 (0.91 to 1.05)	0.19 (0.12 to 0.29)	<.001
≥6	1235	0.31 (0.23 to 0.41)	3409	2.00 (1.82 to 2.18)	1.69 (1.48 to 1.88)	0.16 (0.09 to 0.30)	<.001
mRNA-1273
1	47 976	0.03 (0.02 to 0.05)	140 573	0.05 (0.04 to 0.07)	0.02 (–0.008 to 0.05)	0.62 (0.37 to 1.03)	.06
2	42 349	0.05 (0.03 to 0.07)	124 044	0.09 (0.08 to 0.11)	0.04 (0.01 to 0.07)	0.38 (0.17 to 0.83)	.02
3	25 144	0.07 (0.05 to 0.10)	74 323	0.17 (0.15 to 0.20)	0.10 (0.07 to 0.13)	0.32 (0.16 to 0.67)	.002
4	296	0.12 (0.09 to 0.17)	794	0.57 (0.37 to 0.89)	0.45 (0.19 to 0.71)	0.20 (0.10 to 0.37)	<.01

^a Cohorts were exact matched in a 1:3 ratio by sex, 5-year age group, nationality, and calendar week of first vaccine dose.

^b Standard errors of failure functions were used to derive the 95% CIs of the absolute difference in cumulative incidence at different follow-up times.

^c Hazard ratios were adjusted by sex, 5-year age group, 10 nationality groups (described in Tables 1 and 2), and calendar week of first vaccine dose.