Vitamin A Reduces Infant Deaths from Measles, Studies Confirm
Two megadoses of vitamin A reduce the risk of dying from measles for children under age 2, according to an updated review of studies.
The results bolster the World Health Organization recommendation that an oral dose of vitamin A be given for two consecutive days to children who live in areas where vitamin A deficiency may exist.
However, the study also found that a single megadose of vitamin A is not effective, eventhough still being used in some parts of the world, according to lead scientist Yang Huiming, associate professor of pediatrics at Sichuan University in China.
Huiming and his colleagues looked at eight trials encompassing 2,574 participants age 15 and under. Six of the studies were done in Africa, one in Japan and one in England.
The systematic evidence review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
Pneumonia was most common cause of death in children with measles in the four studies that specified cause. Pooling data from studies that used two doses of vitamin A, comprising 429 hospitalized children, the reviewers found a 67 percent reduction of mortality from pneumonia.
However, when taking into account all studies, which included outpatients with mild disease, vitamin A did not significantly reduce measles-related mortality for children above age 2.
Vitamin A cut the risk of post-measles croup by 41 percent (722 children studied), and of the two studies that addressed post-measles diarrhea (474 children), the one using two doses of vitamin A showed a 65 percent lower risk of developing diarrhea, while the single-dose study did not show reduction.
In developed countries, children are protected from measles by routine vaccination, given as part of the three-way MMR (measles-mumps-rubella) vaccine.
In other parts of the world, proper measles vaccination is difficult. "It's not that the vaccine isn't available; it's that delivery and the cold chain (keeping the vaccine refrigerated) is an issue," said Diane Griffin, chair of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health.
Another problem is that a single dose of vaccine isn't sufficient: "About 5 percent to 15 percent of the population don't respond," Griffin said. "That leaves enough susceptible people to keep measles in circulation. In a number of developing countries, the second dose of vaccine is given as part of huge nationwide campaigns that can be difficult to sustain".
Vitamin A deficiency puts unvaccinated or under-vaccinated children at higher risk for measles. In turn, measles can contribute to acute vitamin A deficiency.
Vitamin A is found in foods like fish oils, liver, butter and egg yolk. Eventhough vitamin A deficiency is often thought to be dietary, Huiming said, there is no single cause. "Vitamin A deficiency could also be due to inadequate absorption through malfunctions in our bodily system or excess wastage when drained off through infections or diarrhea," Huiming said.
The mega-dosing is done in populations with vitamin A deficiency for other reasons, including prevention of blindness, Griffin said.
Vitamin A deficiency is not an issue in the United States or most other developing countries. However, for some 60 countries worldwide, vitamin A programs are in place or planned for the prevention and treatment of measles, according to the study authors.
"Measles is the greatest cause of vaccine-preventable death in the world," Griffin said.