Table 1. Participants' characteristics at baseline by exposure status at the end of the follow-up period, cohort age ≥ 80 years, COVID-19 vaccine effectiveness study, Portugal, 15 May–31 July 2022 (n = 642,067).
| Unvaccinated (n = 51,411) | Primary series (n = 44,284) | First booster (n = 204,362) | Second booster (n = 342,010) | |||||
|---|---|---|---|---|---|---|---|---|
| n | % | n | % | n | % | n | % | |
| Age in years, median (IQR) | 86.0 (82.0–90.0) | 85.0 (82.0–88.0) | 84.0 (82.0–88.0) | 84.0 (82.0–88.0) | ||||
| Age group (years) | ||||||||
| 80–84 | 21,320 | 41.5 | 20,930 | 47.3 | 106,473 | 52.1 | 175,554 | 51.3 |
| 85–89 | 16,285 | 31.7 | 14,838 | 33.5 | 65,368 | 32.0 | 113,156 | 33.1 |
| 90–94 | 9,410 | 18.3 | 6,614 | 14.9 | 25,967 | 12.7 | 43,222 | 12.6 |
| ≥ 95 | 4,396 | 8.6 | 1,902 | 4.3 | 6,554 | 3.2 | 10,078 | 2.9 |
| Male sex | 18,065 | 35.1 | 14,080 | 31.8 | 74,941 | 36.7 | 138,906 | 40.6 |
| Region | ||||||||
| ARS Alentejo | 2,315 | 4.5 | 2,565 | 5.8 | 12,558 | 6.1 | 19,618 | 5.7 |
| ARS Algarve | 3,941 | 7.7 | 3,190 | 7.2 | 9,922 | 4.9 | 13,141 | 3.8 |
| ARS Centro | 9,275 | 18.0 | 8,455 | 19.1 | 41,654 | 20.4 | 68,354 | 20.0 |
| ARS LVT | 18,036 | 35.1 | 16,513 | 37.3 | 74,848 | 36.6 | 120,956 | 35.4 |
| ARS Norte | 11,785 | 22.9 | 13,054 | 29.5 | 64,190 | 31.4 | 118,863 | 34.8 |
| Missing | 6,059 | 11.8 | 507 | 1.1 | 1,190 | 0.6 | 1,078 | 0.3 |
| European deprivation index quintile | ||||||||
| Q1 (least deprived) | 6,462 | 12.6 | 5,975 | 13.5 | 32,086 | 15.7 | 56,305 | 16.5 |
| Q2 | 6,524 | 12.7 | 6,266 | 14.1 | 31,689 | 15.5 | 51,919 | 15.2 |
| Q3 | 6,336 | 12.3 | 6,192 | 14.0 | 29,000 | 14.2 | 50,771 | 14.8 |
| Q4 | 12,445 | 24.2 | 12,226 | 27.6 | 57,324 | 28.1 | 97,586 | 28.5 |
| Q5 (most deprived) | 13,585 | 26.4 | 13,118 | 29.6 | 53,073 | 26.0 | 84,351 | 24.7 |
| Missing | 6,059 | 11.8 | 507 | 1.1 | 1,190 | 0.6 | 1,078 | 0.3 |
| Number of chronic diseases | ||||||||
| 0 | 20,039 | 39.0 | 7,012 | 15.8 | 26,410 | 12.9 | 39,716 | 11.6 |
| 1 | 10,846 | 21.1 | 9,491 | 21.4 | 40,555 | 19.8 | 66,821 | 19.5 |
| 2 | 9,411 | 18.3 | 10,897 | 24.6 | 51,631 | 25.3 | 87,130 | 25.5 |
| 3 | 6,168 | 12.0 | 8,395 | 19.0 | 42,510 | 20.8 | 73,868 | 21.6 |
| 4 | 3,091 | 6.0 | 5,048 | 11.4 | 25,607 | 12.5 | 44,013 | 12.9 |
| ≥ 5 | 1,856 | 3.6 | 3,441 | 7.8 | 17,649 | 8.6 | 30,462 | 8.9 |
| Number of SARS-CoV-2 tests | ||||||||
| 0 | 36,601 | 71.2 | 17,492 | 39.5 | 75,411 | 36.9 | 148,877 | 43.5 |
| 1 | 6,657 | 12.9 | 8,834 | 19.9 | 43,415 | 21.2 | 69,375 | 20.3 |
| 2 | 3,068 | 6.0 | 5,222 | 11.8 | 26,217 | 12.8 | 42,123 | 12.3 |
| 3 | 1,708 | 3.3 | 3,224 | 7.3 | 16,536 | 8.1 | 25,322 | 7.4 |
| 4–9 | 2,802 | 5.5 | 7,399 | 16.7 | 34,249 | 16.8 | 47,183 | 13.8 |
| ≥ 10 | 575 | 1.1 | 2,113 | 4.8 | 8,534 | 4.2 | 9,130 | 2.7 |
| Any other vaccine uptakea | 8,610 | 16.7 | 23,952 | 54.1 | 168,146 | 82.3 | 311,662 | 91.1 |
ARS: regional health administration; COVID-19: coronavirus disease; LVT: Lisbon and Tagus Valley; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2.
a Received at least one of the following vaccines since 2017, influenza vaccine, pneumococcal conjugate vaccines (PCV13, PCV7 or PCV10) and pneumococcal polysaccharide vaccine (PPSV23).