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 1
Characteristics of patients in the study sample, by severe acute respiratory syndrome coronavirus 2 variant of concern, Portugal, epidemiologic weeks 20–26 (May 17–July 4), 2021
| Characteristic | Delta (B.1.617.2), no. (%) | Alpha (B.1.1.7), no. (%) | Total, no. (%) |
|---|---|---|---|
| Overall |
1,366 (100) |
731 (100) |
2,097 (100) |
| Week of diagnosis | |||
| 20 | 53 (4) | 137 (19) | 190 (9) |
| 21 | 64 (5) | 154 (21) | 218 (10) |
| 22 | 112 (8) | 171 (23) | 283 (13) |
| 23 | 192 (14) | 114 (16) | 306 (15) |
| 24 | 249 (18) | 73 (10) | 322 (15) |
| 25 | 350 (26) | 38 (5) | 388 (19) |
| 26 |
346 (25) |
44 (6) |
390 (19) |
| Age group, y | |||
| 40–49 | 760 (56) | 378 (52) | 1,138 (54) |
| 50–69 | 474 (35) | 313 (43) | 787 (38) |
| >70 |
132 (10) |
40 (5) |
172 (8) |
| Sex | |||
| F | 707 (52) | 402 (55) | 1,109 (53) |
| M | 659 (48) | 329 (45) | 988 (47) |
1These first authors contributed equally to this article.
2Members of the PT-Covid-19 Group are listed at the end of this article.
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