Table 5 Sensitivity analysis for bolus or monthly administration of vitamin D

Sensitivity analysis

 Bolus or monthly administration [30, 36,37,38, 43, 46,47,48, 51, 53, 55, 63, 66,67,68]

15; 27,668

0.99 (0.96–1.03)

0.99 (0.94–1.05)

0.99 (0.93–1.06)

1.00 (0.98–1.03)

Subgroups

 Age group (years)

  < 7 [30, 37, 51, 67]

4; 4133

NA

NA

NA

0.99 (0.85–1.16)

  7–17 [55]

1; 62

NA

NA

NA

1.01 (0.99–1.03)

  18–65 [38, 46, 47]

3; 812

NA

NA

NA

0.99 (0.95–1.03)

  > 65 [36, 43, 48, 53, 63, 66, 68]

7; 22,661

0.99 (0.97–1.00)

0.99 (0.95–1.01)

0.98 (0.94–1.01)

0.99 (0.97–1.02)

 Gender proportion (%)

  Male > 60 [36, 47, 51, 67]

4; 1056

NA

NA

NA

1.08 (1.03–1.13)

  Male ≤ 60 [30, 37, 38, 43, 46, 48, 53, 55, 63, 66, 68]

11; 26,612

0.99 (0.98–1.00)

0.99 (0.97–1.00)

0.98 (0.96–1.00)

0.99 (0.97–1.02)

 Comorbidity

  General [37, 38, 43, 48, 53, 63, 66, 68]

8; 25,847

0.99 (0.98–1.01)

0.99 (0.96–1.01)

0.98 (0.95–1.01)

0.99 (0.98–1.01)

  Disease-specific [30, 36, 46, 47, 51, 55, 67]

7; 1821

0.96 (0.87–1.07)

0.95 (0.83–1.09)

0.9 (0.84–1.08)

0.99 (0.93–1.06)

 Baseline 25-hydroxyvitamin D levels (nmol/L)

  < 50 [36, 43, 46,47,48, 55]

6; 1209

0.96 (0.91–1.01)

0.93 (0.85–1.03)

0.92 (0.82–1.03)

1.01 (0.99–1.03)

  > 50 [38, 53, 63, 66]

4; 6326

NA

NA

NA

1.00 (0.97–1.04)

 Trial duration (months)

  < 4 [30]

1; 453

NA

NA

NA

0.77 (0.63–0.94)

  4–12 [51, 67]

2; 634

NA

NA

NA

1.08 (1.04–1.13)

  > 12 [36,37,38, 43, 46,47,48, 53, 55, 63, 66, 68]

12; 26,581

0.99 (0.98–1.00)

0.99 (0.97–1.00)

0.98 (0.96–1.00)

1.00 (0.99–1.01)

 Climatic zone

  Tropical or Subtropical [67]

1; 310

NA

NA

NA

1.08 (1.04–1.13)

  Temperate [30, 36,37,38, 43, 46,47,48, 51, 53, 55, 63, 66, 68]

14; 27,358

0.99 (0.98–1.00)

0.98 (0.97–1.00)

0.98 (0.96–1.00)

1.00 (0.98–1.02)

 Summer

  Summer-inclusive [36,37,38, 43, 46,47,48, 51, 53, 55, 63, 66,67,68]

14; 27,215

1.00 (0.98–1.03)

1.00 (0.96–1.06)

1.01 (0.96–1.07)

1.01 (0.99–1.03)

  Summer-sparing [30]

1; 453

NA

NA

NA

0.77 (0.63–0.94)

 Winter

  Winter-dominant [30]

1; 453

NA

NA

NA

0.77 (0.63–0.94)

  Winter-non-dominant [36,37,38, 43, 46,47,48, 51, 53, 55, 63, 66,67,68]

14; 27,215

1.00 (0.98–1.03)

1.01 (0.96–1.06)

1.01 (0.96–1.07)

1.01 (0.99–1.03

Sensitivity analysis

 Type of ARIs

  Mixed upper and lower respiratory tract infections [48, 53, 55, 63, 66, 67]

6; 6422

1.14 (0.00-NA)

1.25 (0.00-NA)

1.29 (0.00-NA)

1.03 (0.99–1.07)

  Upper respiratory tract infections [38, 43, 46, 47, 68]

5; 17,241

0.99 (0.97–1.01)

0.98 (0.95–1.02)

0.98 (0.94–1.02)

0.98 (0.97–1.00)

  Lower respiratory tract infections [30, 36, 37, 51]

4; 4005

NA

NA

NA

0.96 (0.79–1.16)

  Influenza [53, 55]

2; 169

NA

NA

NA

0.89 (0.61–1.29)