Australian infants had a lower estimated prevalence of egg allergy following a national shift toward earlier egg introduction, according to a population-based study published in JAMA Pediatrics.
Researchers compared 2 cohorts of infants aged 11 to 15 months recruited through immunization centers in Melbourne, Australia: 5,276 infants enrolled from 2007 to 2011, before infant feeding guidelines were updated, and 1,933 infants enrolled from 2018 to 2019, after Australian guidelines began recommending introduction of egg and other allergenic foods during the first year of life.
The median age at egg introduction decreased from 8 months to 6 months between the cohorts. The proportion of infants introduced to egg by 6 months of age increased from 25% to 57%.
Egg allergy was assessed using skin prick testing followed by oral food challenges when indicated. The outcome also included recent reactions consistent with oral food challenge stopping criteria or anaphylaxis to egg in infants with positive skin prick test results.
After multiple imputation, egg allergy prevalence was estimated at 9.2% in the earlier cohort. When the later cohort was standardized to the earlier cohort's distribution of known allergy risk factors, estimated prevalence was 7.6%, an absolute reduction of 1.6 percentage points and a relative reduction of approximately 18%. The whole-cohort finding narrowly met statistical significance.
The reduction was more pronounced among infants with early eczema, defined as eczema beginning within the first 6 months of life and treated with topical steroids. In that subgroup, estimated egg allergy prevalence decreased from 34.6% to 21.9%. Researchers did not observe a similar reduction among infants without early eczema.
The investigators used direct regression standardization to account for temporal differences in factors associated with food allergy risk, including family history of food allergy, parent country of birth, preterm birth, pet dog ownership, number of siblings, and early eczema. The later cohort included a higher proportion of infants with parents born in East Asia, a demographic previously associated with higher food allergy risk in Australia.
Several limitations may affect interpretation of the findings. The study compared cohorts from different time periods rather than randomly assigning feeding practices, leaving open the possibility that unmeasured factors contributed to the observed differences. Participation in skin prick testing was lower in the later cohort, age at egg introduction was reported retrospectively by parents, and data on egg consumption frequency were available only for the later cohort, so its contribution could not be evaluated.
"The guideline update recommending earlier egg introduction in Australia was associated with a shift toward earlier egg introduction and a corresponding reduction in egg allergy prevalence at the population level," wrote lead study researcher Jennifer J. Koplin, PhD, of The University of Queensland and Murdoch Children's Research Institute, and colleagues.
In an accompanying editorial, Aaron E. Carroll, MD, of AcademyHealth, and Ron Keren, MD, of Children's Hospital of Philadelphia and the Perelman School of Medicine at the University of Pennsylvania, argued that the findings provide evidence that food-allergy prevention recommendations supported by randomized trial data can translate into measurable changes at the population level when widely adopted.
The editorialists also offered a critique of earlier avoidance-based guidance, arguing that recommendations to delay allergenic foods were issued with more confidence than the available evidence supported. They wrote that the experience should prompt stronger evidence grading, regular reassessment of recommendations, and investment in clinical trials before firm guidance is issued.
However, the population-level effect observed in Australia may not directly translate to settings with lower uptake. The editorialists noted that 57% of infants in Australia's 2018 to 2019 cohort were introduced to egg by 6 months of age, compared with about 16% of infants in the US who were introduced to egg before 7 months of age in 2021.
Disclosures: The study was funded by the National Health and Medical Research Council of Australia. Several researchers reported grants, consulting fees, speaker fees, advisory roles, patents, or other relationships with organizations involved in allergy research and therapeutics. The editorialists reported no conflicts of interest.
Source: JAMA Pediatrics
