Periods
Different time periods are specified for the analysis:
- The data extraction period: Data extraction is foreseen from the first date of a documented SARS-CoV-2 infection in the population until the most recent date at which data is available at the time of analysis. All individuals vaccinated with at least one dose of the SARS-CoV-2 vaccine (any of the available brands) and all individuals eligible to be vaccinated with a documented positive diagnosis (irrespective of the type of test) for SARS-CoV-2 infection during the data extraction period are included in the study population.
- The enrollment period: A sequence of nested (daily) trials are emulated with increasing time (t1, t2, …, tn), iterating over the days in the enrollment period. At each eligible time during the enrollment period, the vaccination status of eligible individuals is assessed and every individual who has completed a primary vaccination schedule at that time (treated/exposed) is matched to an individual who has not (yet) completed the primary vaccination schedule (control).
- The study period: The study period is considered from the start of the enrollment period until one year after the end of the enrollment period, to allow a minimal possible follow-up period of one year.
Period | Time range |
---|---|
Data extraction period | 2020-03-05 - 2022-05-20 |
Enrollment period | 2021-01-01 - 2021-08-31 |
Study period | 2021-01-01 - 2022-08-31 |
Study population and enrollment
A flow diagram displaying the process of obtaining a matched study population considered for survival analysis.
Description of the study population: table 1
Intervention group (Completed a primary vaccination schedule) (N=8378) |
Control group (Not completed a primary vaccination schedule) (N=949) |
P-value | |
---|---|---|---|
ᵃ5-year age groups | |||
sex_cd | |||
Mean (SD) | 1.47 (0.537) | 1.48 (0.541) | 0.356 |
Median [Min, Max] | 1.00 [0, 2.00] | 2.00 [0, 2.00] | |
age_cdᵃ | |||
Mean (SD) | 11.6 (2.96) | 11.6 (3.00) | 0.914 |
Median [Min, Max] | 12.0 [2.00, 18.0] | 12.0 [2.00, 18.0] | |
residence_area_cd | |||
731 | 1170 (14.0%) | 139 (14.6%) | 0.574 |
732 | 1182 (14.1%) | 123 (13.0%) | |
733 | 6026 (71.9%) | 687 (72.4%) | |
institutionalized_bl | |||
Yes | 233 (2.8%) | 28 (3.0%) | 0.845 |
No | 8145 (97.2%) | 921 (97.0%) | |
foreign_bl | |||
Yes | 1271 (15.2%) | 123 (13.0%) | 0.0782 |
No | 7107 (84.8%) | 826 (87.0%) | |
pregnancy_bl | |||
Yes | 99 (1.2%) | 20 (2.1%) | 0.0241 |
No | 8279 (98.8%) | 929 (97.9%) | |
essential_worker_bl | |||
Yes | 231 (2.8%) | 27 (2.8%) | 0.959 |
No | 8147 (97.2%) | 922 (97.2%) | |
comorbidities_bl | |||
Yes | 3852 (46.0%) | 451 (47.5%) | 0.384 |
No | 4526 (54.0%) | 498 (52.5%) | |
immunestatus_bl | |||
Yes | 2349 (28.0%) | 250 (26.3%) | 0.287 |
No | 6029 (72.0%) | 699 (73.7%) |
Intervention group (Completed a primary vaccination schedule) (N=8126) |
Control group (Not completed a primary vaccination schedule) (N=8126) |
P-value | |
---|---|---|---|
ᵃ5-year age groups | |||
sex_cd | |||
Mean (SD) | 1.46 (0.537) | 1.45 (0.549) | 0.179 |
Median [Min, Max] | 1.00 [0, 2.00] | 1.00 [0, 2.00] | |
age_cdᵃ | |||
Mean (SD) | 11.6 (2.96) | 11.6 (2.99) | 0.607 |
Median [Min, Max] | 12.0 [2.00, 18.0] | 12.0 [2.00, 18.0] | |
residence_area_cd | |||
731 | 1133 (13.9%) | 1170 (14.4%) | 0.00891 |
732 | 1144 (14.1%) | 1012 (12.5%) | |
733 | 5849 (72.0%) | 5944 (73.1%) | |
institutionalized_bl | |||
Yes | 225 (2.8%) | 217 (2.7%) | 0.736 |
No | 7901 (97.2%) | 7909 (97.3%) | |
foreign_bl | |||
Yes | 1234 (15.2%) | 1232 (15.2%) | 0.983 |
No | 6892 (84.8%) | 6894 (84.8%) | |
pregnancy_bl | |||
Yes | 97 (1.2%) | 83 (1.0%) | 0.33 |
No | 8029 (98.8%) | 8043 (99.0%) | |
essential_worker_bl | |||
Yes | 226 (2.8%) | 224 (2.8%) | 0.962 |
No | 7900 (97.2%) | 7902 (97.2%) | |
comorbidities_bl | |||
Yes | 3736 (46.0%) | 3721 (45.8%) | 0.826 |
No | 4390 (54.0%) | 4405 (54.2%) | |
immunestatus_bl | |||
Yes | 2280 (28.1%) | 2287 (28.1%) | 0.917 |
No | 5846 (71.9%) | 5839 (71.9%) |
Two-by-two tables
The individuals in the imported dataset are counted by ‘fully_vaccinated_bl’ and ‘confirmed_case_bl’.
Confirmed case | Not confirmed case | Total | |
---|---|---|---|
Completed a primary vaccination schedule | 2990 | 6010 | 9000 |
Not completed a primary vaccination schedule | 361 | 639 | 1000 |
Total | 3351 | 6649 | 10000 |
Ratio = \(\frac{(\frac{confirmed \ cases}{primary vaccinated \ individuals})} {(\frac{confirmed \ cases}{not-primary vaccinated \ individuals})}\) = 0.9202832
The individuals eligible for analysis are counted by ‘fully_vaccinated_bl’ and ‘confirmed_case_bl’.
Confirmed case | Not confirmed case | Total | |
---|---|---|---|
Completed a primary vaccination schedule | 2639 | 5739 | 8378 |
Not completed a primary vaccination schedule | 329 | 620 | 949 |
Total | 2968 | 6359 | 9327 |
Ratio = \(\frac{(\frac{confirmed \ cases}{primary vaccinated \ individuals})} {(\frac{confirmed \ cases}{not-primary vaccinated \ individuals})}\) = 0.9085929
The matched individuals are counted by ‘fully_vaccinated_bl’ and ‘confirmed_case_bl’.
Confirmed case | Not confirmed case | Total | |
---|---|---|---|
Completed a primary vaccination schedule | 2617 | 5715 | 8332 |
Not completed a primary vaccination schedule | 242 | 560 | 802 |
Total | 2859 | 6275 | 9134 |
Ratio = \(\frac{(\frac{confirmed \ cases}{primary vaccinated \ individuals})} {(\frac{confirmed \ cases}{not-primary vaccinated \ individuals})}\) = 1.0409107
Survival in un-matched population
Variable | Beta (SE) | HR (95% CI) | P |
---|---|---|---|
fully_vaccinated_blTRUE | -0.02 (0.07) | 0.98 (0.86, 1.11) | 0.71 |
Strata | Time | Number at risk | Cumulative sum of number of events | Cumulative sum of number censored | Survival | Std. error | Cumulative hazard | Std. error cumulative hazard |
---|---|---|---|---|---|---|---|---|
|
0 | 902 | 1 | 0 | 0.9988914 | 0.0011080327 | 0.0011086475 | 0.0011086475 |
|
1 | 901 | 2 | 0 | 0.9977827 | 0.0015661251 | 0.0022185254 | 0.0015687346 |
|
100 | 887 | 15 | 0 | 0.9833703 | 0.0042579213 | 0.0167601671 | 0.0043275070 |
|
200 | 881 | 21 | 0 | 0.9767184 | 0.0050209720 | 0.0235436859 | 0.0051377719 |
|
300 | 869 | 33 | 0 | 0.9634146 | 0.0062511087 | 0.0372477521 | 0.0064843714 |
|
400 | 693 | 212 | 0 | 0.7649667 | 0.0141183086 | 0.2674750096 | 0.0184246060 |
|
500 | 621 | 281 | 0 | 0.6884701 | 0.0154201697 | 0.3726241520 | 0.0223575550 |
|
600 | 620 | 282 | 0 | 0.6873614 | 0.0154351407 | 0.3742344580 | 0.0224154712 |
|
0 | 8378 | 1 | 0 | 0.9998806 | 0.0001193531 | 0.0001193602 | 0.0001193602 |
|
1 | 8377 | 2 | 0 | 0.9997613 | 0.0001687807 | 0.0002387347 | 0.0001688109 |
|
100 | 8253 | 126 | 0 | 0.9849606 | 0.0013297021 | 0.0151514274 | 0.0013498093 |
|
200 | 3885 | 594 | 3997 | 0.9149921 | 0.0034433135 | 0.0887960657 | 0.0037611165 |
|
300 | 2645 | 1072 | 4665 | 0.7759389 | 0.0065510625 | 0.2534754869 | 0.0084351389 |
|
400 | 2307 | 1195 | 4885 | 0.7394797 | 0.0070201758 | 0.3015773379 | 0.0094855960 |
|
500 | 786 | 1200 | 6446 | 0.7378440 | 0.0070426699 | 0.3037910797 | 0.0095371385 |
|
600 | 7 | 1200 | 7171 | 0.7378440 | 0.0070426699 | 0.3037910797 | 0.0095371385 |
Variable | Beta (SE) | HR (95% CI) | P |
---|---|---|---|
fully_vaccinated_blTRUE | -0.02 (0.07) | 0.98 (0.86, 1.11) | 0.73 |
age_cd | 0.00 (0.01) | 1.00 (0.99, 1.02) | 0.64 |
sex_cd | -0.05 (0.05) | 0.95 (0.86, 1.04) | 0.26 |
residence_area_cd | |||
731 (ref) | – | – | – |
732 | 0.04 (0.10) | 1.04 (0.85, 1.28) | 0.67 |
733 | 0.14 (0.08) | 1.15 (0.99, 1.34) | 0.07 |
essential_worker_blTRUE | 0.03 (0.15) | 1.03 (0.76, 1.39) | 0.84 |
institutionalized_blTRUE | 0.20 (0.14) | 1.22 (0.92, 1.61) | 0.17 |
foreign_blTRUE | -0.04 (0.07) | 0.96 (0.83, 1.11) | 0.60 |
comorbidities_blTRUE | 0.02 (0.05) | 1.02 (0.92, 1.13) | 0.75 |
immunestatus_blTRUE | 0.01 (0.06) | 1.01 (0.90, 1.13) | 0.93 |