Table 2 Factors associated with breakthrough infection (n = 6076)

From: Levels of SARS-CoV-2 antibodies among fully vaccinated individuals with Delta or Omicron variant breakthrough infections

 

Breakthrough infections

PDFUa

Univariable

Multivariable

 

n

 

IRR (95% CI)

p-value

aIRR (95% CI)

p-value

Total spike quintiles (log 10)

≤1.77

44

242,045

1.00

 

1.00

 

1.77–2.29

45

242,074

1.02 (0.68–1.54)

0.91

0.68 (0.45–1.02)

0.06

2.29–2.69

78

241,982

1.77 (1.23–2.56)

0.002

0.75 (0.52–1.09)

0.13

2.69–3.02

114

242,134

2.59 (1.84–3.65)

<0.0001

0.79 (0.56–1.11)

0.17

>3.02

223

241,968

5.07(3.68–6.98)

<0.0001

0.71 (0.51–0.98)

0.03

Age at enrollment (per 10 years older)

  

0.97 (0.96–0.97)

<0.0001

0.97 (0.97–0.98)

<0.0001

Sex

 Male

201

543,681

1.00

 

1.00

 

 Female

303

666,522

1.23 (1.03–1.46)

0.02

0.98 (0.82–1.17)

0.78

Healthcare worker

 No

443

1,124,364

1.00

 

1.00

 

 Yes

61

85,839

1.80 (1.40–2.32)

<0.0001

1.18 (0.89–1.55)

0.24

Transmission levelb

 Low

7

310,364

1.00

 

1.00

 

 Intermediate

36

569,908

2.60 (1.25–6.29)

0.01

2.80 (1.25–6.30)

0.01

 High

51

134,818

16.77 (7.61–36.95)

<0.0001

16.56 (7.49–36.64)

<0.0001

 Very high

410

195,113

93.17 (44.15–196.62)

<0.0001

94.49 (44.58–200.30)

<0.0001

  1. Incidence rate ratios (IRR) and adjusted incidence rate ratios (aIRR) for breakthrough infections modelled in a univariable and multivariable poisson logistic regression model, with two-sided chi-squared tests for each variable in the model.
  2. aPerson-days of follow-up.
  3. bLow: <10 cases/100,000 population/day, moderate: 10–40 cases/100,000 population/day, high: 41–85 cases/100,000 population/day and very high: >85 cases/100,000 population/day.