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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 Kislaya1Comments to Author , Eduardo Freire Rodrigues1, Vítor Borges, João P. Gomes, Carlos Sousa, José P. Almeida, André Peralta-Santos, Baltazar Nunes, and PT-COVID-19 Group2
Author affiliations: Instituto Nacional de Saúde Doutor Ricardo Jorge, Lisbon, Portugal (I. Kislaya, V. Borges, J.P. Gomes, B. Nunes); Direção-Geral da Saúde, Lisbon (E.F. Rodrigues, A. Peralta-Santos); Unilabs, Porto, Portugal (C. Sousa, J.P. Almeida)

Main Article

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.

Main Article

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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