Table 3.
One step individual participant data meta-analysis, proportion of participants experiencing at least one acute respiratory tract infection (ARTI): overall and by subgroup, stratified by dosing frequency
| Variables | Bolus dosing | Daily or weekly dosing | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| No of trials* | Proportion with ≥1 ARTI, control group (%) | Proportion with ≥1 ARTI, intervention group (%) | Adjusted odds ratio (95% CI)† | P value | P value for interaction | No of trials* | Proportion with ≥1 ARTI, control group (%) | Proportion with ≥1 ARTI, intervention group (%) | Adjusted odds ratio (95% CI)† | P value | P value for interaction | ||
| Overall | 10 | 994/2786 (35.7) | 1097/3014 (36.4) | 0.97 (0.86 to 1.10) | 0.67 | -- | 15 | 1210/2439 (49.6) | 1206/2694 (44.8) | 0.81 (0.72 to 0.91) | 0.001 | -- | |
| Baseline 25(OH)D (nmol/L): | |||||||||||||
| <25 | 8 | 73/142 (51.4) | 77/162 (47.5) | 0.82 (0.51 to 1.33) | 0.43 | 0.42 | 6 | 64/107 (59.8) | 40/127 (31.5) | 0.30 (0.17 to 0.53) | <0.001 | 0.006 | |
| ≥25 | 8 | 550/910 (60.4) | 663/1121 (59.1) | 1.02 (0.83 to 1.24) | 0.87 | 11 | 477/729 (65.4) | 516/874 (59.0) | 0.75 (0.60 to 0.95) | 0.02 | |||
| Daily dose equivalent (µg): | |||||||||||||
| <20 | . | . | . | . | . | 0.56 | 5 | 629/1321 (47.6) | 619/1435 (43.1) | 0.80 (0.68 to 0.94) | 0.006 | 0.82 | |
| 20-50 | 3 | 467/1931 (24.2) | 542/2127 (25.5) | 0.95 (0.81 to 1.10) | 0.50 | 6 | 478/865 (55.3) | 481/950 (50.6) | 0.81 (0.66 to 1.01) | 0.06 | |||
| ≥50 | 7 | 527/855 (61.6) | 555/887 (62.6) | 1.03 (0.83 to 1.28) | 0.81 | 4 | 103/253 (40.7) | 106/309 (34.3) | 0.85 (0.58 to 1.24) | 0.39 | |||
| Age (years): | |||||||||||||
| ≤1 | 2 | 321/1634 (19.6) | 322/1637 (19.7) | 0.99 (0.83 to 1.19) | 0.93 | 0.72 | 2 | 511/1110 (46.0) | 532/1190 (44.7) | 0.91 (0.77 to 1.08) | 0.30 | 0.37 | |
| 1.1-15.9 | 1 | 50/100 (50.0) | 35/93 (37.6) | 0.62 (0.35 to 1.11) | 0.11 | 7 | 191/413 (46.2) | 159/473 (33.6) | 0.59 (0.45 to 0.79) | <0.001 | |||
| 16-65 | 8 | 432/678 (63.7) | 466/716 (65.1) | 1.15 (0.90 to 1.48) | 0.27 | 9 | 422/781 (54.0) | 419/876 (47.8) | 0.79 (0.63 to 0.99) | 0.04 | |||
| >65 | 8 | 191/374 (51.1) | 274/568 (48.2) | 0.85 (0.65 to 1.12) | 0.25 | 3 | 86/135 (63.7) | 96/155 (61.9) | 0.88 (0.52 to 1.52) | 0.66 | |||
| Body mass index (kg/m2): | |||||||||||||
| <25 | 8 | 215/372 (57.8) | 231/417 (55.4) | 1.01 (0.72 to 1.40) | 0.97 | 0.70 | 11 | 757/1571 (48.2) | 725/1657 (43.8) | 0.82 (0.71 to 0.95) | 0.009 | >0.99 | |
| ≥25 | 8 | 406/677 (60.0) | 509/867 (58.7) | 1.00 (0.80 to 1.25) | 0.98 | 9 | 253/358 (70.7) | 245/367 (66.8) | 0.83 (0.59 to 1.17) | 0.30 | |||
| Asthma: | |||||||||||||
| No | 5 | 303/484 (62.6) | 323/523 (61.8) | 0.95 (0.71 to 1.28) | 0.75 | 0.40 | 6 | 215/524 (41.0) | 197/578 (34.1) | 0.74 (0.58 to 0.95) | 0.02 | 0.40 | |
| Yes | 4 | 224/371 (60.4) | 232/364 (63.7) | 1.18 (0.85 to 1.65) | 0.32 | 7 | 72/163 (44.2) | 53/178 (29.8) | 0.60 (0.37 to 0.98) | 0.04 | |||
| COPD: | |||||||||||||
| No | 5 | 410/632 (64.9) | 436/656 (66.5) | --‡ | --‡ | --‡ | 2 | 67/131 (51.1) | 57/135 (42.2) | --‡ | --‡ | --‡ | |
| Yes | 4 | 117/223 (52.5) | 119/231 (51.5) | --‡ | --‡ | --‡ | 2 | 5/7 (71.4) | 1/7 (14.3) | --‡ | --‡ | --‡ | |
| Influenza vaccination | |||||||||||||
| No | 5 | 119/163 (73.0) | 121/178 (68.0) | --‡ | --‡ | --‡ | 5 | 136/210 (64.8) | 132/229 (57.6) | --‡ | --‡ | --‡ | |
| Yes | 5 | 286/396 (72.2) | 294/421 (69.8) | . | . | . | 5 | 278/383 (72.6) | 283/405 (69.9) | ||||
25(OH)D=25-hydroxyvitamin D; COPD=chronic obstructive pulmonary disease; 1 µg vitamin D3=40 international units (IU).
*Some trials did not contribute data to a given subgroup, either because individuals within that subgroup were not represented or because data relating to the potential effect modifier were not recorded; accordingly the number of trials represented varies between subgroups.
†Adjusted for age, sex, and study duration.
‡Values could not be estimated as models did not converge.