Acute lower respiratory tract infections (LRTIs), especially pneumonia and bronchiolitis, are leading causes of mortality in children up to five years of age. The Global Burden of Disease 2000 project estimated that the annual number of acute respiratory tract infection (ARTI)-related deaths in children up to five years of age was 2.1 million (excluding deaths caused by measles, whooping cough and neonatal deaths). Others estimate worldwide child deaths from ARTIs at 1.9 million in 2000, 70% of them in Africa and Southeast Asia. Vitamin A deficiency is common in low-income countries and weakens barriers to infection.
We included 10 trials (33,179 children) where vitamin A deficiency or malnutrition was prevalent (31,379 in the community and 1800 in a hospital setting). Studies measured different aspects (for example, what constituted 'acute LRTI', the time to symptom resolution, etc.). There may have been other treatments (especially of malnourished children) which could have led to bias. Most studies showed no significant benefit of vitamin A supplements on the incidence or prevalence of symptoms of acute LRTIs. Although no included studies addressed adverse effects of vitamin A, the use of vitamin A should be carefully monitored.
We do not recommend giving vitamin A to all children to prevent acute LRTIs because a few studies unexpectedly found that vitamin A increased the chance of infections or worsened symptoms in otherwise healthy children. Some evidence shows benefit for vitamin supplements given to children with low serum retinol or with a poor nutritional status. Limitations of our review include trials conducted within very specific populations and poor methodological quality of some of the included trials.