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Volume 28, Number 2—February 2022

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 2

Crude and adjusted odds ratio of being infected with severe acute respiratory syndrome coronavirus 2 and vaccinated (odds of vaccine infection breakthrough) in Delta-infected versus Alpha-infected patients, Portugal, epidemiologic weeks 20–26 (May 17–July 4), 2021*

Vaccination status Delta, no. (%) Alpha, no. (%) Crude OR (95% CI) Confounder-adjusted† OR (95% CI)
Unvaccinated 777 (57) 517 (78) Referent Referent
1 dose (<14 d) 229 (17) 73 (10) 1.23 (0.83 to 1.82) 1.29 (0.85 to 1.95)
1 dose (>14 d) or 2 doses (<14 d)‡ 198 (14) 49 (7) 1.70 (1.18 to 2.47) 1.81 (1.37 to 2.39)
2 doses (>14 d)§ 162 (12) 38 (5) 1.96 (1.43 to 2.69) 1.96 (1.22 to 3.14)

*OR, odds ratio. †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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