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The impact of shifting demographics, variants of concern and vaccination on outcomes during the first 3 COVID-19 waves in Alberta and Ontario: a retrospective cohort study

Finlay A. McAlister, Majid Nabipoor, Anna Chu, Douglas S. Lee, Lynora Saxinger and Jeffrey A. Bakal; on behalf of the CORONA Collaboration
April 26, 2022 10 (2) E400-E408; DOI: https://doi.org/10.9778/cmajo.20210323

Article Figures & Tables

Tables

  • Table 1:

    Demographics and outcomes for those with SARS-CoV-2 infection in Alberta and Ontario — Mar. 1, 2020, to June 30, 2021

    CharacteristicWave 1 (Mar. 2020 to Oct. 2020)Wave 2 (Nov. 2020 to Jan. 2021)Wave 3 (Feb. 2021 to June 2021)Totalp value*
    No. of people with a positive SARS-CoV-2 test100 478271 592359 079731 149–
    Age, yr, n (%)
     < 1810 274 (10.2)36 367 (13.4)66 349 (18.5)112 990 (15.5)< 0.0001
     18–3935 754 (35.6)96 585 (35.6)132 911 (37.0)265 250 (36.3)< 0.0001
     40–6537 986 (37.8)103 488 (38.1)132 022 (36.8)273 496 (37.4)< 0.0001
     > 6516 464 (16.4)35 152 (12.9)27 797 (7.7)79 413 (10.9)< 0.0001
    Age, yr, median (IQR)
     Alberta36 (23–51)36 (23–52)33 (19–47)35 (21–49)< 0.0001
     Ontario43 (27–60)40 (25–57)36 (23–52)38 (24–55)< 0.0001
    Male, n (%)48 523 (48.3)133 329 (49.1)182 622 (50.9)364 474 (49.8)< 0.0001
    Rural resident, n (%)4968 (4.9)18 713 (6.9)24 116 (6.7)47 797 (6.5)< 0.0001
    Deprivation Index, n (%)
     Missing2373 (2.4)7409 (2.7)8927 (2.5)18 709 (2.6)< 0.0001
     Q1 (least deprived)16 782 (16.7)44 020 (16.2)62 711 (17.5)123 513 (16.9)
     Q216 809 (16.7)47 136 (17.4)65 702 (18.3)129 647 (17.7)
     Q318 004 (17.9)50 495 (18.6)66 885 (18.6)135 384 (18.5)
     Q418 909 (18.8)54 169 (19.9)69 639 (19.4)142 717 (19.5)
     Q5 (most deprived)27 601 (27.5)68 363 (25.2)85 215 (23.7)181 179 (24.8)
    In a long-term care facility, n (%)7832 (7.8)10 202 (3.8)826 (0.2)18 860 (2.6)< 0.0001
    Charlson Comorbidity Index score, n (%)
     0/missing90 174 (89.7)249 436 (91.8)334 113 (93)673 723 (92.1)< 0.0001
     12278 (2.3)4479 (1.6)3337 (0.9)10 094 (1.4)
     21526 (1.5)2983 (1.1)2334 (0.6)6843 (0.9)
     3+6500 (6.5)14 694 (5.4)19 295 (5.4)40 489 (5.5)
    Specific comorbidities, n (%)
     COPD or asthma804 (0.8)1723 (0.6)1207 (0.3)3734 (0.5)< 0.0001
     Other chronic lung disease (non-COPD/asthma)29 (0)65 (0)56 (0)150 (0)0.01
     Congestive heart failure1005 (1)1813 (0.7)1275 (0.4)4093 (0.6)< 0.0001
     Hypertension3100 (3.1)5614 (2.1)4053 (1.1)12 767 (1.7)< 0.0001
     Diabetes mellitus2655 (2.6)5280 (1.9)4231 (1.2)12 166 (1.7)< 0.0001
     CAD (including previous MI, CABG or PCI/stent)898 (0.9)1996 (0.7)1901 (0.5)4795 (0.7)< 0.0001
     Peripheral vascular disease218 (0.2)424 (0.2)335 (0.1)977 (0.1)< 0.0001
     Cerebrovascular disease (previous stroke/TIA)678 (0.7)1110 (0.4)699 (0.2)2487 (0.3)< 0.0001
     Atrial fibrillation/flutter1174 (1.2)1943 (0.7)1256 (0.3)4373 (0.6)< 0.0001
     Ventricular arrhythmias67 (0.1)152 (0.1)130 (0)349 (0)< 0.0001
     Renal disease489 (0.5)988 (0.4)725 (0.2)2202 (0.3)< 0.0001
     Cancer706 (0.7)1654 (0.6)1752 (0.5)4112 (0.6)< 0.0001
     Peptic ulcer disease178 (0.2)298 (0.1)282 (0.1)758 (0.1)< 0.0001
     Liver disease191 (0.2)559 (0.2)544 (0.2)1294 (0.2)< 0.0001
     Dementia1968 (2)2602 (1)621 (0.2)5191 (0.7)< 0.0001
    Vaccination status, n (%)
     Fully vaccinated0 (0)8 (0)2500 (0.7)2508 (0.3)< 0.0001
     Partially vaccinated0 (0)733 (0.3)22 378 (6.2)23 111 (3.2)
     Unvaccinated100 478 (100)270 851 (99.7)334 201 (93.1)705 530 (96.5)
    Death
     Death within 30 days, n (%)3423 (3.4)4800 (1.8)2639 (0.7)10 862 (1.5)< 0.0001
     Age at death, yr, median (IQR)
      Alberta85 (77–91)85 (75–91)74 (63–85)84 (73–90)< 0.0001
      Ontario86 (78–91)85 (76–91)76 (66–85)83 (73–90)< 0.0001
     Male, n (%)1604 (46.9)2479 (51.6)1548 (58.7)5631 (51.8)< 0.0001
     Days to death, median (IQR)
      Alberta7 (3–12)8 (4–13)9 (4–15)8 (4–13)0.009
      Ontario9 (5–14)11 (7–17)12 (6–19)11 (6–17)< 0.0001
    All-cause hospitalization
     Hospital admission within 30 days7036 (7)13 025 (4.8)20 256 (5.6)40 317 (5.5)< 0.0001
     Age at hospitalization, yr, median (IQR)
      Alberta63 (47–76)65 (48–80)54 (40–67)59 (44–74)< 0.0001
      Ontario68 (54–81)70 (55–82)60 (46–73)64 (50–77)< 0.0001
     Male, n (%)3737 (53.1)6977 (53.6)11 047 (54.5)21 761 (54)0.02
     Length of stay, d, median (IQR)
      Alberta6 (3–12)7 (3–13)5 (3–10)6 (3–11)< 0.0001
      Ontario8 (3–20)7 (3–14)6 (3–12)7 (3–13)< 0.0001

    • Note: CABG = coronary artery bypass graft, CAD = coronary artery disease, COPD = chronic obstructive pulmonary disease, IQR = interquartile range, MI = myocardial infarction, PCI = percutaneous coronary intervention, TIA = transient ischemic attack.

    • ↵* Waves 1 and 2 versus wave 3.

  • Table 2:

    Demographics and outcomes for those with SARS-CoV-2 infection in Alberta and Ontario by variant — Feb. 1, 2021, to June 30, 2021 (wave 3)

    CharacteristicWild-typeAlpha variantDelta variantOther variantsNot tested/ indeterminateTotalp value
    No. of people with a positive SARS-CoV-2 test92 427182 020370832 16448 760359 079–
    Age, yr, n (%)
     < 1819 884 (21.5)31 875 (17.5)702 (18.9)5439 (16.9)8449 (17.3)66 349 (18.5)< 0.0001
     18–3931 017 (33.6)69 101 (38.0)1409 (38.0)12 440 (38.7)18 944 (38.9)132 911 (37)
     40–6534 832 (37.7)67 697 (37.2)1290 (34.8)11 652 (36.2)16 551 (33.9)132 022 (36.8)
     > 656694 (7.2)13 347 (7.3)307 (8.3)2633 (8.2)4816 (9.9)27 797 (7.7)
    Age, yr, median (IQR)
     Alberta32 (18–47)33 (20–47)32 (20–45)35 (22–48)NA33 (19–47)< 0.0001
     Ontario36 (23–54)36 (23–52)35 (22–52)36 (22–52)36 (22–53)36 (23–52)< 0.0001
    Male, n (%)47 217 (51.1)92 315 (50.7)1898 (51.2)16 700 (51.9)24 492 (50.2)182 622 (50.9)< 0.0001
    Rural resident, n (%)9317 (10.1)9856 (5.4)301 (8.1)1608 (5)3034 (6.2)24 116 (6.7)< 0.0001
    Deprivation Index, n (%)
     Missing3902 (4.2)3231 (1.8)69 (1.9)482 (1.5)1243 (2.5)8927 (2.5)< 0.0001
     Q1 (least deprived)15 183 (16.4)32 650 (17.9)589 (15.9)5407 (16.8)8882 (18.2)62 711 (17.5)
     Q215 997 (17.3)34 327 (18.9)621 (16.7)5807 (18.1)8950 (18.4)65 702 (18.3)
     Q317 047 (18.4)34 328 (18.9)664 (17.9)6001 (18.7)8845 (18.1)66 885 (18.6)
     Q416 983 (18.4)36 044 (19.8)747 (20.1)6576 (20.4)9289 (19.1)69 639 (19.4)
     Q5 (most deprived)23 315 (25.2)41 440 (22.8)1018 (27.5)7891 (24.5)11 551 (23.7)85 215 (23.7)
    In a long-term care facility, n (%)326 (0.4)165 (0.1)32 (0.9)53 (0.2)250 (0.5)826 (0.2)< 0.0001
    Charlson Comorbidity Index score, n (%)
     0/missing87 775 (95)169 547 (93.1)3368 (90.8)29 602 (92)43 821 (89.9)334 113 (93)< 0.0001
     1943 (1)1475 (0.8)35 (0.9)263 (0.8)621 (1.3)3337 (0.9)
     2610 (0.7)1081 (0.6)29 (0.8)212 (0.7)402 (0.8)2334 (0.6)
     3+3099 (3.4)9917 (5.4)276 (7.4)2087 (6.5)3916 (8)19 295 (5.4)
    Specific comorbidities, n (%)
     COPD or asthma360 (0.4)534 (0.3)7 (0.2)113 (0.4)193 (0.4)1207 (0.3)< 0.0001
     Other chronic lung disease (non-COPD/asthma)16 (0)23 (0)1–5*1–5*10 (0)56 (0)0.02
     Congestive heart failure331 (0.4)577 (0.3)12 (0.3)113 (0.4)242 (0.5)1275 (0.4)< 0.0001
     Hypertension1001 (1.1)1936 (1.1)46 (1.2)351 (1.1)719 (1.5)4053 (1.1)< 0.0001
     Diabetes mellitus1124 (1.2)1935 (1.1)52 (1.4)366 (1.1)754 (1.5)4231 (1.2)< 0.0001
     CAD (including previous MI, CABG or PCI/stent)443 (0.5)919 (0.5)22 (0.6)174 (0.5)343 (0.7)1901 (0.5)< 0.0001
     Peripheral vascular disease83 (0.1)147 (0.1)3 (0.1)36 (0.1)66 (0.1)335 (0.1)0.008
     Cerebrovascular disease (previous stroke/TIA)185 (0.2)312 (0.2)8 (0.2)54 (0.2)140 (0.3)699 (0.2)< 0.0001
     Atrial fibrillation/flutter330 (0.4)535 (0.3)18 (0.5)110 (0.3)263 (0.5)1256 (0.3)< 0.0001
     Ventricular arrhythmias31 (0)63 (0)1–5*17 (0.1)17 (0)130 (0)0.5
     Renal disease181 (0.2)348 (0.2)1–5*53 (0.2)139 (0.3)725 (0.2)0.0002
     Cancer417 (0.5)831 (0.5)18 (0.5)169 (0.5)317 (0.7)1752 (0.5)< 0.0001
     Peptic ulcer disease72 (0.1)124 (0.1)1–5*27 (0.1)55 (0.1)282 (0.1)0.04
     Liver disease173 (0.2)198 (0.1)8 (0.2)43 (0.1)122 (0.3)544 (0.2)< 0.0001
     Dementia181 (0.2)212 (0.1)9 (0.2)51 (0.2)168 (0.3)621 (0.2)< 0.0001
    Vaccination status, n (%)
     Fully vaccinated334 (0.4)925 (0.5)111 (3)195 (0.6)935 (1.9)2500 (0.7)< 0.0001
     Partially vaccinated3823 (4.1)11 722 (6.4)1010 (27.2)2100 (6.5)3723 (7.6)22 378 (6.2)
     Unvaccinated88 270 (95.5)169 373 (93.1)2587 (69.8)29 869 (92.9)44 102 (90.4)334 201 (93.1)
    Death
     Death within 30 days, n (%)532 (0.6)1384 (0.8)52 (1.4)325 (1)346 (0.7)2639 (0.7)< 0.0001
     Age at death, yr, median (IQR)
      Alberta75 (63–86)74 (65–85)72 (69–80)66 (56–73)NA74 (63–85)0.01
      Ontario79 (70–87)75 (65–84)73 (60–86)74 (65–84)78 (66–86)76 (66–85)< 0.0001
     Male, n (%)302 (56.8)822 (59.4)30 (57.7)202 (62.2)192 (55.5)1548 (58.7)< 0.0001
     Days to death, median (IQR)
      Alberta8 (3–14)9 (4–17)12 (4–18)9 (3–14)NA9 (4–15)0.4
      Ontario11 (6–17)12 (7–19)16 (11–21)13 (6–20)10 (4–16)12 (6–19)< 0.0001
    All-cause hospitalization
     Hospital admission within 30 days3470 (3.8)11 552 (6.3)295 (8)2321 (7.2)2618 (5.4)20 256 (5.6)< 0.0001
     Age at hospitalization, yr, median (IQR)
      Alberta55 (38– 69)54 (41–66)57 (39–69)53 (40–62)NA54 (40–67)0.3
      Ontario63 (48–77)59 (46–71)57 (43–70)60 (48–72)61 (41–75)60 (46–73)< 0.0001
     Male, n (%)1878 (54.1)6284 (54.4)169 (57.3)1335 (57.5)1381 (52.8)11 047 (54.5)< 0.0001
     Length of stay, d, median (IQR)
      Alberta5 (3–10)5 (3–10)6 (3–10)6 (3–10)NA5 (3–10)0.8
      Ontario6 (3–11)6 (3–11)6 (3–11)7 (3–12)6 (2–11)6 (3–12)< 0.0001

    • Note: CABG = coronary artery bypass graft, CAD = coronary artery disease, COPD = chronic obstructive pulmonary disease, IQR = interquartile range, MI = myocardial infarction, NA = not available, PCI = percutaneous coronary intervention, TIA = transient ischemic attack.

    • ↵* Cells with values of less than 5 have been suppressed for privacy reasons.

  • Table 3:

    Outcome associations during wave 3, stratified by variant of concern and vaccination status*

    VariableAll-cause hospitalization, aOR (95% CI)Death, aOR (95% CI)
    AlbertaOntarioPooledAlbertaOntarioPooled
    Variant of concern
     Wild-typeReference
     Alpha variant1.86 (1.73–2.00)1.48 (1.41–1.56)1.59 (1.53–1.66)1.64 (1.32–2.04)1.19 (1.05–1.35)1.29 (1.16–1.44)
     Delta variant2.7 (1.91–3.81)1.76 (1.52–2.04)1.88 (1.64–2.15)4.97 (2.37–10.43)1.67 (1.17–2.38)2.05 (1.49–2.82)
    Vaccination status
     UnvaccinatedReference
     Partially vaccinated0.44 (0.38–0.51)0.42 (0.39–0.44)0.42 (0.40–0.45)0.61 (0.46–0.81)0.40 (0.35–0.46)0.43 (0.38–0.49)
     Fully vaccinated0.55 (0.36–0.83)0.18 (0.15–0.22)0.22 (0.18–0.26)0.98 (0.55–1.77)0.33 (0.25–0.45)0.41 (0.32–0.53)

    • Note: aOR = adjusted odds ratio, CI = confidence interval.

    • ↵* Adjusted for age, sex and Charlson Comorbidity Index score.

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CMAJ Open: 10 (2)
Vol. 10, Issue 2
1 Apr 2022

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The impact of shifting demographics, variants of concern and vaccination on outcomes during the first 3 COVID-19 waves in Alberta and Ontario: a retrospective cohort study
Finlay A. McAlister, Majid Nabipoor, Anna Chu, Douglas S. Lee, Lynora Saxinger, Jeffrey A. Bakal
Apr 2022, 10 (2) E400-E408; DOI: 10.9778/cmajo.20210323
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