The Effect of Vitamin A Supplementation at Birth on the Development of Atopy in Childhood: Long-term Follow-up of a Randomised Placebo-controlled Trial

INTRODUCTION Eight trials studying the effect of providing neonatal vitamin A supplementation (NVAS) have been reported, and another four are underway to test whether NVAS should become WHO policy. Three of the four African trials were conducted by the Bandim Health Project (BHP) in Guinea-Bissau. One of them was a two-by-two factorial trial among low-birth-weight children. From 2004-2008, the children were randomly allocated to 25,000 IU vitamin A or placebo at birth, and furthermore to BCG vaccination at birth or later as is local policy. In 2011, the investigators conducted a follow-up study. A remarkably strong harmful effect of NVAS on atopy and wheezing was found (manuscript under review).

Seen in the context that NVAS may soon become a WHO policy it is obviously worrying if NVAS is associated with a higher risk of atopy and wheezing. The investigators therefore aim to conduct a similar follow-up study of participants in the first NVAS trial conducted in Guinea-Bissau from 2002-2004, among normal-birth-weight infants, to test whether NVAS is associated with an increased risk of atopy and wheezing and other allergic symptoms as well as growth.

METHODS

Study population:

From 2002-2004 BHP conducted a randomised trial of NVAS. The investigators recruited newborns when they came for BCG vaccination. Provided parental consent, they received an oral supplement of 50,000 IU vitamin A or placebo.

Study design:

This study will be a follow-up study of the cohort of children randomised to NVAS (intervention) or placebo (current policy) together with BCG vaccine at birth.

Other exposures:

The investigators will also investigate the effect of receiving an additional dose of measles vaccine and the timing of DTP vaccine on the development of atopy.

Assessment of outcomes:

The investigators will visit all children at the last known address. Height, weight and mid upper arm circumference will be measured. BCG scar will be examined and vaccination card details recorded by the field assistant. Children will be excluded from skin prick testing (SPT) if they have a history suggestive of anaphylaxis or are currently using anti-histamine medication. SPT will be performed using aero-allergens, food allergens and positive histamine and negative saline control. The mother or guardian will be interviewed by a local assistant. Symptoms of eczema and asthma as well as food allergy will be assessed.

Statistical analysis:

Effect of randomisation group and other factors on outcomes will be analysed in multivariable regression models. All analyses will be adjusted for skin prick tester. All analyses will be conducted stratified by sex.