Table 1.
Description of participants’ characteristics across all waves and results of the multivariable analysis. Odds ratios are presented for all variables that were part of the final model after variable selection. The effect of “Participation in previous rounds” interacted with the gender and time effect, the latter of which is depicted in Fig. 2. “Province” was not taken up in the model; instead, we used a two-dimensional spline to assess the spatial effect (Fig. 3). “Household composition” was removed from the model during backwards model selection. For “COVID-19 vaccine willingness”, unweighted and weighted percentages are shown, “(unweighted/weighted)”. Note that percentages may not sum exactly to 100% due to rounding.
| Participants (%) | Vaccine willingness % unweighted/weighted |
Vaccine willingness OR (95% CI) | ||
|---|---|---|---|---|
| Participation date | ||||
| July 14 | 24,756 (10.7) | 89.2/89.9 | REF | |
| July 28 | 32,219 (13.9) | 89.3/90.0 | 0.96 (0.84–1.11) | |
| August 25 | 22,788 (9.9) | 80.7/82.6 | 0.47 (0.42–0.53) | |
| September 08 | 20,490 (8.9) | 78.1/80.7 | 0.40 (0.36–0.45) | |
| September 22 | 17,722 (7.7) | 77.7/80.2 | 0.38 (0.34–0.43) | |
| November 03 | 22,953 (9.9) | 81.8/83.1 | 0.49 (0.44–0.56) | |
| November 17 | 23,902 (10.3) | 82.1/83.1 | 0.47 (0.41–0.53) | |
| December 01 | 20,813 (9.0) | 81.0/81.7 | 0.43 (0.38–0.48) | |
| December 15 | 19,953 (8.6) | 83.1/83.9 | 0.44 (0.39–0.50) | |
| December 29 | 25,383 (11.0) | 85.1/85.9 | 0.48 (0.42–0.55) | |
| Participation in previous waves | ||||
| Every wave | 59,901 (25.9) | 85.3/86.1 | ||
| A few waves/often | 159,621 (69.1) | 82.9/84.0 | Fig. 2 | |
| Once | 5,549 (2.4) | 79.7/79.6 | ||
| No | 5,908 (2.6) | 78.0/76.5 | ||
| Gender | ||||
| Female | 159,449 (69.0) | 80.9/81.0 | ||
| Male | 71,530 (31.0) | 88.8/87.3 | ||
| (Gender, Participation in previous waves) | ||||
| (Female, every wave) | 42,376 (18.3) | 82.8/82.3 | REF | |
| (Male, every wave) | 17,525 (7.6) | 91.5/90.7 | 2.10 (1.99–2.22) | |
| (Female, a few waves/often) | 110,844 (48.0) | 80.4/80.9 | REF | |
| (Male, a few waves/often) | 48,777 (21.1) | 88.6/87.2 | 1.64 (1.59–1.69) | |
| (Female, once) | 3,238 (1.4) | 76.5/75.3 | REF | |
| (Male, once) | 2,311 (1.0) | 84.1/82.0 | 1.60 (1.41–1.81) | |
| (Female, No) | 2,991 (1.3) | 74.9/74.3 | REF | |
| (Male, No) | 2,917 (1.3) | 81.1/77.4 | 1.27 (1.12–1.43) | |
| Age | ||||
| 18–30 | 21,762 (9.4) | 81.7/82.4 | REF | |
| 31–50 | 77,798 (33.7) | 78.4/79.0 | 0.93 (0.89–0.96) | |
| 51–70 | 113,766 (49.3) | 85.7/86.5 | 1.36 (1.30–1.42) | |
| 71+ | 17,653 (7.6) | 91.8/91.2 | 1.80 (1.69–1.92) | |
| Province | ||||
| Antwerp | 113,218 (49.0) | 83.4/84.3 | ||
| East Flanders | 39,999 (17.3) | 83.3/84.3 | ||
| Flemish Brabant | 34,438 (14.9) | 84.9/85.8 | Fig. 3 | |
| Limburg | 20,389 (8.8) | 81.4/82.4 | ||
| West Flanders | 22,935 (9.9) | 82.3/83.4 | ||
| Educational attainment | ||||
| Primary education | 2,870 (1.2) | 79.8/80.7 | 0.62 (0.56–0.68) | |
| Secondary education | 62,423 (27.0) | 80.2/80.8 | 0.72 (0.70–0.74) | |
| Higher education | 158,370 (68.6) | 84.3/85.0 | REF | |
| PhD | 7,316 (3.2) | 90.7/91.3 | 1.54 (1.42–1.66) | |
| Family size | ||||
| Single | 43,790 (19.0) | 81.6/83.0 | REF | |
| Two persons | 95,104 (41.2) | 86.7/87.4 | 1.20 (1.16–1.24) | |
| 3–5 persons | 87,013 (37.7) | 80.9/81.5 | 1.14 (1.10–1.17) | |
| 5 + persons | 5,072 (2.2) | 76.5/77.2 | 0.89 (0.82–0.95) | |
| Family composition | ||||
| Children age 12 or lower | 37,743 (16.3) | 78.2/78.7 | NS | |
| Children age 13 or higher | 31,402 (13.6) | 78.6/79.0 | NS | |
| Elderly above 70 | 21,778 (9.4) | 89.1/90.2 | NS | |
| Financial situation | ||||
| Very easy | 52,932 (22.9) | 89.0/89.3 | REF | |
| Easy | 89,584 (38.8) | 85.5/86.0 | 0.80 (0.77–0.82) | |
| Somewhat easy | 64,433 (27.9) | 80.2/81.4 | 0.62 (0.60–0.65) | |
| Somewhat difficult | 20,459 (8.9) | 72.5/73.2 | 0.43 (0.41–0.45) | |
| Difficult | 3,571 (1.5) | 62.8/61.5 | 0.27 (0.25–0.29) | |
| Employment statute/sector | ||||
| Employee/official | 79,718 (34.5) | 82.2/82.5 | REF | |
| Student | 7,087 (3.1) | 83.4/84.4 | 1.35 (1.27–1.43) | |
| Labourer | 4,692 (2.0) | 70.9/69.2 | 0.62 (0.58–0.66) | |
| Education | 18,946 (8.2) | 83.2/83.9 | 1.07 (1.02–1.12) | |
| Health worker | 13,634 (5.9) | 80.9/80.9 | 1.05 (1.00–1.11) | |
| Self-employed | 11,339 (4.9) | 78.5/79.4 | 0.78 (0.74–0.83) | |
| Unemployed | 22,646 (9.8) | 76.8/76.8 | 0.86 (0.83–0.90) | |
| Retired | 66,194 (28.7) | 89.6/90.4 | 1.36 (1.30–1.43) | |
| Other | 6,723 (2.9) | 78.2/79.9 | 0.95 (0.89–1.01) | |
| Know someone with severe COVID-19 symptoms | ||||
| Yes | 132,953 (57.6) | 83.9/84.8 | 1.18 (1.16–1.21) | |
| No | 98,026 (42.4) | 82.5/83.2 | REF | |
| Underlying medical conditions | ||||
| Heart condition | 11,438 (5.0) | 88.9/89.0 | 1.04 (0.98–1.11) | |
| Lung condition | 12,817 (5.5) | 87.0/87.3 | 1.34 (1.27–1.42) | |
| Kidney disease | 2,521 (1.1) | 85.5/86.6 | 0.97 (0.87–1.10) | |
| Diabetes | 9,550 (4.1) | 89.7/90.8 | 1.43 (1.33–1.53) | |
| High blood pressure | 35,724 (15.5) | 88.0/88.7 | 1.22 (1.18–1.27) | |
| Immune suppression | 8,889 (3.8) | 83.4/84.7 | 1.25 (1.17–1.34) | |
| Recent cancer diagnosis | 3,231 (1.4) | 87.5/89.1 | 1.27 (1.13–1.42) | |
| COVID-19 vaccine willingness | ||||
| Definitely | 137,851 (59.7/61.2) | |||
| Probably | 54,609 (23.6/23.0) | |||
| Maybe | 24,293 (10.5/9.8) | |||
| Probably not | 9,109 (3.9/3.9) | |||
| Definitely not | 5,117 (2.2/2.2) | |||
OR: odds ratio, CI: confidence interval, NS: not selected, REF: reference level.