Table 2. Association Between Receipt of Influenza Vaccines in the 2019-2020 and 2020-2021 Cohorts, PHE in 2018-2019, and Study Outcomes.
| 2019-2020 Cohort | 2020-2021 Cohort | PHE, 2018-2019a | ||||
|---|---|---|---|---|---|---|
| Vaccinated | Unvaccinated | Vaccinated | Unvaccinated | Yes | No | |
| No. of individuals (%) | 1 229 487 (53.9) | 1 050 318 (46.1) | 1 266 939 (57.8) | 924 604 (42.2) | 342 800 (15.0) | 1 937 005 (85.0) |
| SARS-CoV-2 infection | ||||||
| No. of events (%) | 2584 (0.21) | 2745 (0.26) | 13 188 (1.04) | 15 227 (1.65) | 748 (0.22) | 4582 (0.24) |
| Unadjusted HR (95% CI) | 0.79 (0.75-0.83) | 1 [Reference] | 0.73 (0.71-0.75) | 1 [Reference] | 0.91 (0.84-0.98) | 1 [Reference] |
| Age-sex adjusted HR (95% CI) | 0.76 (0.72-0.80) | 1 [Reference] | 0.73 (0.71-0.75) | 1 [Reference] | 0.95 (0.88-1.03) | 1 [Reference] |
| Fully adjusted HR (95% CI)b | 0.78 (0.73-0.84) | 1 [Reference] | 0.76 (0.74-0.78) | 1 [Reference] | 0.85 (0.78-0.91) | 1 [Reference] |
| SARS-CoV-2–associated hospitalization | ||||||
| No. of events (%) | 992 (0.08) | 980 (0.09) | 3508 (0.28) | 4704 (0.51) | 273 (0.08) | 1939 (0.10) |
| Unadjusted HR (95% CI) | 0.84 (0.77-0.92) | 1 [Reference] | 0.68 (0.65-0.71) | 1 [Reference] | 0.79 (0.70-0.90) | 1 [Reference] |
| Age-sex adjusted HR (95% CI) | 0.78 (0.72-0.86) | 1 [Reference] | 0.68 (0.65-0.71) | 1 [Reference] | 0.85 (0.75-0.97) | 1 [Reference] |
| Fully adjusted HR (95% CI)b | 0.83 (0.75-0.93) | 1 [Reference] | 0.68 (0.64-0.72) | 1 [Reference] | 0.79 (0.69-0.90) | 1 [Reference] |
| SARS-CoV-2–associated death | ||||||
| No. of events (%) | 428 (0.03) | 441 (0.04) | 1210 (0.10) | 1862 (0.20) | 106 (0.03) | 791 (0.04) |
| Unadjusted HR (95% CI) | 0.82 (0.72-0.93) | 1 [Reference] | 0.60 (0.56-0.65) | 1 [Reference] | 0.77 (0.63-0.94) | 1 [Reference] |
| Age-sex adjusted HR (95% CI) | 0.73 (0.64-0.84) | 1 [Reference] | 0.60 (0.55-0.64) | 1 [Reference] | 0.88 (0.72-1.08) | 1 [Reference] |
| Fully adjusted HR (95% CI)b | 0.74 (0.62-0.87) | 1 [Reference] | 0.58 (0.53-0.63) | 1 [Reference] | 0.82 (0.67-1.01) | 1 [Reference] |
| SARS-CoV-2–associated hospitalization or death | ||||||
| No. of events (%) | 1104 (0.09) | 1093 (0.10) | 3788 (0.30) | 5160 (0.56) | 289 (0.08) | 2060 (0.11) |
| Unadjusted HR (95% CI) | 0.84 (0.77-0.91) | 1 [Reference] | 0.66 (0.64-0.69) | 1 [Reference] | 0.79 (0.70-0.90) | 1 [Reference] |
| Age-sex adjusted HR (95% CI) | 0.78 (0.71-0.85) | 1 [Reference] | 0.66 (0.64-0.69) | 1 [Reference] | 0.86 (0.76-0.97) | 1 [Reference] |
| Fully adjusted HR (95% CI)b | 0.83 (0.74-0.92) | 1 [Reference] | 0.66 (0.63-0.70) | 1 [Reference] | 0.80 (0.70-0.90) | 1 [Reference] |
| SARS-CoV-2 testing | ||||||
| No. of events (%) | 209 077 (17.0) | 154 845 (14.7) | 254 093 (20.1) | 183 217 (19.8) | 48 986 (14.3) | 314 937 (16.3) |
| Unadjusted OR (95% CI) | 1.19 (1.18-1.19) | 1 [Reference] | 1.02 (1.01-1.02) | 1 [Reference] | 0.86 (0.85-0.87) | 1 [Reference] |
| Age-sex adjusted OR (95% CI) | 1.17 (1.16-1.17) | 1 [Reference] | 1.02 (1.01-1.03) | 1 [Reference] | 0.89 (0.88-0.90) | 1 [Reference] |
| Fully adjusted OR (95% CI)b | 1.05 (1.04-1.06) | 1 [Reference] | 0.91 (0.90-0.92) | 1 [Reference] | 0.91 (0.90-0.92) | 1 [Reference] |
Abbreviations: HR, hazard ratio; OR, odds ratio; PHE, periodic health examination.
a
We assessed the association between PHE and COVID-19 outcomes in the 2019-2020 cohort.
b
Adjusted for age, sex, comorbidities, past health care utilization, receipt of previous-year influenza vaccination, PHE (past year), neighborhood income quintile, rurality, public health unit region, and census variables.