Table 2.
Main studies on vitamin A supplementation against viral infections.
| Study | Author | Study Population | Micronutrient (Dosage) | Results |
|---|---|---|---|---|
| Vitamin A and respiratory syncytial virus infection. Serum level and supplementation trial. | Kyran P 1996 [37] | Children RCT |
Vitamin A (100,000 UI) | Lower mean vitamin A levels in RSV-infected children than in healthy control (p < 0.05). No significant difference in improvement in clinical outcomes. |
| Treatment of respiratory syncytial virus infection with vitamin A: a randomized placebo-controlled trial in Santiago. | Dowell SF 1996 [38] | Children RCT |
Vitamin A (50,000 to 200,000 UI, dosed according to age) | More rapid resolution of tachypnea (p = 0.01). Shorter duration of hospitalization (p = 0.09). |
| Vitamin A therapy for children with respiratory syncytial virus infection: a multicenter trial in the United States. | Bresee JS 1996 [39] | Children RCT |
Vitamin A (50,000 to 200,000 UI, dosed according to age) | Not significantly different in the number of days during which supplemental oxygen was required. Not significant difference in the number of days required to achieve normal respiratory rates. |
| Vitamin A supplements and diarrheal and respiratory tract infections among children in Dar es Salaam, Tanzania. | Fawzi WW 2000 [40] | Children RCT |
Vitamin A (100,000 to 200,000 UI, dosed according to age) | Significantly higher risk of cough and rapid respiratory rate (p = 0.004) in treatment group. |
| Vitamin A for preventing acute lowe respiratory tract infections in children up to 7 years of age. | Chen H. 2008 [43] | Children from areas or with conditions correlated with a status of vitamin A deficiency. 10 RCTs |
Vitamin A (6 studies were large-dose trials (100,000 UI o 200,000 UI) 4 studies were low-dose trials (5000 UI daily or 10,000 UI weekly or 45,000 UI every 2 months) | No significant effect on the incidence or prevalence of ALRI symptoms with vitamin A supplementation. |
| Vitamin A supplementation for prophylaxis or therapy in childhood pneumonia: a systematic review of randomized controlled trials. | Mathew JL 2010 [42] | Children 20 RCTs |
Vitamin A (prophylaxis trial: >100,000 UI; therapeutic trials: 100,000 UI o 200,000 UI) | Neither prophylactic nor therapeutic benefit for childhood pneumonia. |
| Vitamin A supplementation every 6 months with retinol in 1 million pre-school children in north India: DEVTA, a cluster-randomized trial. | Awasthi S 2013 [32] | Children RCT |
Vitamin A (200,000 UI 6-monthly) | Not significant mortality reduction. |
| Vitamin A supplementation for preventing morbidity and mortality in children from 6 months to 5 years of age. | Imdad A 2017 [33] | Children 42 RCTs |
Vitamin A (large-dose trials: range of 50,000 UI to 200,000 UI, except for five studies: 3866 UI 3 times a week, 8333 UI once a week, 10,000 UI weekly and 250,000 UI 2 times a week) | 12% reduction in all-cause mortality (RR 0.88 95% CI 0.83 to 0.93) in the interevention group. Not significant difference in ALRI-mortality. Not effect for vitamin A supplementation on ALRI incidence (only 2 trials reported ALRI prevalence, suggesting benefit for vitamin A supplementation). |
ALRI, acute lower respiratory tract infection; CI, confidence interval; RCT, randomized controlled trial; RR, relative risk; RSV, respiratory syncytial virus.