Table 2.
Factors associated with breakthrough infection (n = 6076)
| 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 |
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.
aPerson-days of follow-up.
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.