Experts from the UK and Pakistan looked at studies of 200,000 children, and found that giving under-five year olds the vitamin could cut deaths by 24%.
And taking it would also cut rates of diarrhoea, they said.
Writing in the British Medical Journal, University of Oxford and Aga Khan University researchers calculate that, with an estimated 190m vitamin A deficient children, reducing deaths by 24 per cent would save more than 600,000 lives each year.
Vitamin A deficiency is one of the leading causes of death for children and a major risk factor for pregnant women. It is a major risk for under fives and that risk is higher in children from developing countries. Worldwide, 190 million under fives may have a Vitamin 'A' deficiency, according to estimates from the World Health Organisation (WHO). Therefore, The WHO already hands out vitamin A supplements twice a year in 60 different countries, but there are concerns these supplement programmes don’t reach all the children who need them.
"Until other sources are available, supplements should be given to all children who are at risk of vitamin A deficiency, said Dr Evan Mayo-Wilson from the University of Oxford, who worked on the study.
"After just one year, children who had taken supplements were less likely to have died than children who received a placebo [dummy version].
“Vitamin A supplements are highly effective and cheap to produce and administer."
In Africa, more than three million children under five are blind because of a vitamin A deficiency and 50 million more are at risk of blindness.
Dr Alex Butera, at Rwanda’s King Faisal Hospital, in its capital, Kigali backed the study.
"Its impact on decreasing diseases, especially viral infections, has earned it the name, "anti-infective vitamin", for its role in supporting the activities of the immune system," Dr Butera told the country’s New Times newspaper.
He added that Vitamin A is also involved in maintaining eyesight, the digestive, respiratory, and reproductive systems and therefore impacts on growth, reproduction and bone development.
The BMJ published the study along with an editorial by two experts at Harvard School of Public Health, who said "effort should now focus on finding ways to sustain this important child survival initiative and fine tune it to maximize the number of lives saved."