Volume 28, Number 2—February 2022
Research
Comparative Effectiveness of Coronavirus Vaccine in Preventing Breakthrough Infections among Vaccinated Persons Infected with Delta and Alpha Variants
Irina Kislaya1
, Eduardo Freire Rodrigues1, Vítor Borges, João P. Gomes, Carlos Sousa, José P. Almeida, André Peralta-Santos, Baltazar Nunes, and PT-COVID-19 Group2
, Eduardo Freire Rodrigues1, Vítor Borges, João P. Gomes, Carlos Sousa, José P. Almeida, André Peralta-Santos, Baltazar Nunes, and PT-COVID-19 Group2
Table 4
Sensitivity analysis crude and adjusted odds ratio of being infected and vaccinated (odds of vaccine infection breakthrough) in Delta versus Alpha SARS-CoV-2 cases, Portugal, weeks 20–26 (May 17–July 4), 2021*
| Vaccination status | Delta (B.1.617.2), no. (%) | Alpha (B.1.1.7), no. (%) | Crude OR (95% CI) | Confounder-adjusted† OR (95% CI ) |
|---|---|---|---|---|
| Restricted to epidemiologic weeks 22–26, n = 1,689 | ||||
| Unvaccinated | 682 (55) | 328 (75) | Referent | Referent |
| 1 dose (<14 d) | 224 (18) | 54 (12) | 1.34 (0.94 to 1.91) | 1.38 (0.96 to 1.98) |
| 1 dose (>14 d) or 2 doses (<14 d)‡ | 190 (15) | 32 (7) | 1.87 (1.22 to 2.86) | 1.91 (1.22 to 3.00) |
| 2 doses (>14 d)§ |
153 (12) |
26 (6) |
1.99 (1.25 to 3.16) |
1.78 (1.01 to 3.13) |
| Restricted to WGS-classified VOC patients, n = 931 | ||||
| Unvaccinated | 406 (59) | 189 (77) | Referent | Referent |
| 1 dose (<14 d) | 104 (15) | 29 (12) | 1.21 (0.75 to 1.95) | 1.20 (0.73 to 1.96) |
| 1 dose (>14 d) or 2 doses (<14 d)‡ | 84 (12) | 11 (4) | 2.63 (1.34 to 5.20) | 2.50 (1.23 to 5.08) |
| 2 doses (>14 d)§ |
90 (13) |
18 (7) |
1.91 (1.09 to 3.34) |
1.48 (0.75 to 2.93) |
| Restricted to patients with Ct values <25, n = 1,363 | ||||
| Unvaccinated | 492 (57) | 412 (82) | Referent | Referent |
| 1 dose (<14 d) | 161 (19) | 48 (10) | 1.20 (0.79 to 1.81) | 1.30 (0.85 to 1.98) |
| 1 dose (>14 d) or 2 doses (<14 d)‡ | 142 (17) | 30 (6) | 2.14 (1.32 to 3.46) | 2.47 (1.48 to 4.12) |
| 2 doses (>14 d)§ | 64 (7) | 14 (3) | 1.92 (0.97 to 3.82) | 2.42 (1.06 to 5.51) |
*Ct, cycle threshold; OR, odds ratio; WGS, whole-genome sequencing; VOC, variant of concern. †Adjusted for sex and age group by conditional logistic regression using week of diagnosis result as matching variable. ‡Partial vaccination. §Complete vaccination.
1These first authors contributed equally to this article.
2Members of the PT-Covid-19 Group are listed at the end of this article.
Page created: November 29, 2021
Page updated: January 22, 2022
Page reviewed: January 22, 2022
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