HOUSTON – The introduction of peanuts at an early age to children who are more highly predisposed to having a peanut allergy can induce tolerance of peanuts and thereby significantly decrease the likelihood of developing a sustained allergy.

This finding from the Learning Early about Peanut Allergy (LEAP) study was presented at the annual meeting of the American Academy of Allergy, Asthma, and Immunology and simultaneously published by the New England Journal of Medicine. Investigators enrolled 640 infants aged 4-11 months between December 2006 and May 6, 2009, all of whom were given skin-prick tests at baseline to determine existing peanut allergies, and randomized them into cohorts that would either consume or avoid peanuts until they reached 60 months of age (N. Engl. J. Med. 2015 Feb. 23 [doi:10.1056/NEJMoa1414850]).

Of the 530 children who had negative skin-prick test results, the prevalence of peanut allergy after 60 months was 13.7% in the avoidance cohort and 1.9% in the consumption cohort (P < .001). Of 98 children who had positive skin-prick test results, 35% of the avoidance cohort had peanut allergy after 60 months, while only 11% of the consumption cohort had the allergy (P = .004). Several children who were initially enrolled and randomized either dropped out or were excluded because of inadequate adherence to treatment or missing data.

Outcomes were measured by placing children in a double-blind, placebo-controlled study that had them consume a cumulative total of 9.4 g of peanut protein to determine whether or not tolerance to peanuts had been effectively induced. All children consumed peanuts by eating peanut butter or a peanut-based snack called Bamba, which was provided for the study at a discounted rate. Children whose skin-prick tests showed wheals of larger than 4 mm in diameter were excluded for presumed existing peanut allergy.

“If you enroll children after 11 months of age, you get about twice the rate of [already allergic] children, with a steady decline as [age] goes down,” corresponding author Dr. Gideon Lack, head of the department of pediatric allergy at King’s College, London, said in a press conference following presentation of the study. “But of children younger than 5 months of age, none of them were peanut allergic, so that would suggest that timing here is key: There is a narrow window of opportunity to intervene if you want to be effective.”

Investigators also noted that children who consumed peanuts had increased levels of IgG4 antibody, while those told to avoid peanuts had higher levels of IgE antibody. They also found that development of peanut allergy was generally associated with subjects who both displayed larger wheals on the skin-prick test and had a lower ratio of IgG4:IgE antibodies. Skin-prick tests that yielded wheals of 1-2 mm in diameter were considered indicative of early risk for peanut allergy.

There was no significant difference in the rates of adverse events or hospitalizations between the consumption and avoidance cohort, but 99% of subjects in each group did experience at least one adverse event: 4,527 in the consumption cohort and 4,287 in the avoidance cohort (P = .02). Infants who consumed peanuts had higher instances of upper respiratory tract infection, viral skin infection, gastroenteritis, urticaria, and conjunctivitis, but events mostly ranged from mild to moderate and their severity was not significantly different from similar incidents reported in the avoidance cohort.

Hospitalization rates also were low, with 52 children in the avoidance cohort and 50 children who consumed peanuts being admitted over the study interval, or 16.2% and 15.7%, respectively (P = .86). Rates of serious adverse effects also were not significantly different between the two cohorts, with 101 children who avoided peanuts and 89 who consumed peanuts experiencing such events (P = .41).

Adequate adherence to treatment for the children randomized into the peanut-avoidance group was defined as eating less than 0.2 g of peanut protein on any single occasion and no more than 0.5 g over the course of a single week in the first 24 months of life. For children in the consumption cohort, adequate adherence meant consuming at least 2 g of peanut protein on at least one occasion in both the first and second years of life, and at least 3 g of peanut protein weekly for at least half the number of weeks for which data was collected.

“Whether or not these benefits can be sustained, we will find out in 1 year,” Dr. Lack said, adding that “all the children who had been consuming peanut have stopped [for] 1 year, and we will see if peanut allergy persists after 1 year of cessation of consumption.” He predicted that the findings would most likely produce a mixed response, with some children relapsing while others maintain sustained tolerance.

The LEAP study was supported by grants from the National Institute of Allergy and Infectious Diseases, Food Allergy and Research Education, the Medical Research Council and Asthma UK, the UK Department of Health’s National Institute for Health Research, the National Peanut Board, and the UK Food Standards Agency. Dr. Lack disclosed financial affiliations with DBV Technologies, and coauthor Dr. Helen Brough disclosed receiving financial support from Fare and Action Medical Research, along with study materials from Stallergenes, Thermo Scientific, and Meridian Foods.


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