Table 2: Placebo controlled RCTs:
Proportion of participants experiencing at least one acute respiratory infection, overall and stratified by potential effect-modifiers
| Potential effect-modifier | No of trials | Proportion with ≥1 ARI, intervention group (%) | Proportion with ≥1 ARI, control group (%) | Odds ratio (95% CI) | I2 % | P for heterogeneity |
|---|---|---|---|---|---|---|
| Overall | 36 | 13685/22288 (61.4) | 13565/21721 (62.5) | 0.91 (0.84 to 0.99) | 37.2 | 0.01 |
| Baseline 25(OH)D, nmol/L[a] | ||||||
| <25 | 19 | 1348/1798 (75.0) | 1388/1819 (76.3) | 0.78 (0.53 to 1.16) | 47.2 | 0.01 |
| 25 – 49.9 | 28 | 3439/4666 (73.7) | 3347/4501 (74.4) | 1.03 (0.92 to 1.15) | 0.4 | 0.46 |
| 50 – 74.9 | 29 | 1679/2839 (59.1) | 1565/2578 (60.7) | 0.90 (0.76 to 1.06) | 11.2 | 0.29 |
| ≥75 | 25 | 945/1543 (61.2) | 908/1471 (61.7) | 0.97 (0.81 to 1.16) | 0.0 | 0.78 |
| Dosing frequency | ||||||
| Daily | 18 | 1056/2134 (49.5) | 1020/1871 (54.5) | 0.75 (0.61 to 0.93) | 52.5 | 0.005 |
| Weekly | 6 | 4482/6421 (69.8) | 4447/6335 (70.2) | 0.97 (0.88 to 1.06) | 0.0 | 0.48 |
| Monthly or less frequently | 12 | 8147/13733 (59.3) | 8098/13515 (59.9) | 0.98 (0.93 to 1.03) | 0.0 | 0.57 |
| Daily dose equivalent, IU[b] | ||||||
| <400 | 2 | 482/1175 (41.0) | 511/1133 (45.1) | 0.65 (0.31 to 1.37) | 86.3 | 0.007 |
| 400–1000 | 10 | 656/1236 (53.1) | 627/1069 (58.7) | 0.70 (0.55 to 0.89) | 31.2 | 0.16 |
| 1001–2000 | 15 | 9946/15885 (62.6) | 10022/15817 (63.4) | 0.97 (0.92 to 1.03) | 1.0 | 0.44 |
| >2000 | 7 | 2291/3462 (66.2) | 2250/3444 (65.3) | 1.05 (0.84 to 1.31) | 37.1 | 0.15 |
| Trial duration, months | ||||||
| ≤12 | 29 | 1977/4887 (40.5) | 1866/4368 (42.7) | 0.82 (0.72 to 0.93) | 38.1 | 0.02 |
| >12 | 7 | 11708/17401 (67.3) | 11699/17353 (67.4) | 0.99 (0.95 to 1.04) | 0.0 | 0.91 |
| Age, yrs[a] | ||||||
| <1 | 5 | 875/2901 (30.2) | 839/2796 (30.0) | 0.95 (0.82 to 1.10) | 18.7 | 0.30 |
| 1–15.9 | 15 | 4297/5994 (71.7) | 4303/5877 (73.2) | 0.71 (0.57 to 0.90) | 46.0 | 0.03 |
| 16–64.9 | 21 | 3137/4876 (64.3) | 3087/4727 (65.3) | 0.97 (0.93 to 1.09) | 11.5 | 0.31 |
| ≥65 | 16 | 5376/8589 (62.6) | 5352/8394 (63.4) | 0.96 (0.90 to 1.02) | 0.0 | 0.67 |
| Airway disease | ||||||
| Asthma only | 4 | 203/404 (50.2) | 202/391 (51.7) | 0.73 (0.36 to 1.49) | 71.7 | 0.01 |
| COPD only | 2 | 106/208 (51.0) | 104/207 (50.2) | 1.01 (0.68 to 1.51) | 0.0 | 0.71 |
| Unrestricted | 30 | 13376/21676 (61.7) | 13259/21123 (62.8) | 0.91 (0.84 to 0.99) | 35.0 | 0.03 |
[a]
The number of trials in each category for this variable adds up to more than 36, since this is a participant-level variable, i.e. some trials contributed data from participants who fell into more than one category