key: cord-0858116-c6nxm3v2 authors: Hurley, Sadhbh; Franklin, Ruth; McCallion, Naomi; Byrne, Aideen M.; Fitzsimons, John; Byrne, Susan; White, Martin; O'Mahony, Liam; Hourihane, Jonathan O’B title: Allergy‐related outcomes at 12 months in the CORAL birth cohort of Irish children born during the first COVID 19 lockdown date: 2022-03-25 journal: Pediatr Allergy Immunol DOI: 10.1111/pai.13766 sha: 87c1800c9c431081a498cdf735749e09b43fe07f doc_id: 858116 cord_uid: c6nxm3v2 nan To the Editor, The CORAL Birth cohort is a unique birth cohort project examin- March and May 2020, during the first SARS-CoV-2 lockdown in Ireland. We hypothesised that the dramatic social and environmental changes imposed by the pandemic-mandated lockdown would have implications on the incidence of allergic conditions, possibly mediated by changes in microbiome diversity. We report here interim data of health outcomes, including allergic conditions, at 12 months in this cohort. We have previously published health outcome data at 6 months. 1 A total of 365 infants were enrolled, and 344 were retained to 12 months. Allergic outcomes in the CORAL cohort were compared with a national pre-pandemic birth cohort from the BASELINE study. 2 The 12-month appointment involved skin prick testing (SPT), assessment of any atopic dermatitis (AD), lateral flow SARS-CoV-2 antibody testing and stool and blood sample for analysis. Patient demographic characteristics for the cohort at 12 months are outlined in Table 1 . Including results from both community-based PCR testing and CORAL appointment antibody testing 16/344 (4.7%), CORAL infants had been diagnosed with SARS-2-CoV by 12 months. Despite the second and third waves prior to 12-month appointments, antibody positivity remained low in infants at 11/344 (3%) ( Table 2) . Return to work was reported by 227/344 (66%) of mothers at 12-month review. This included mothers who returned to work from home. The infant age at return ranged from 2 to 12 months (mean age 9.1 months). There is a statistically significant difference in breastfeeding between working and non-working mothers at 12 months (p < .001). Infants of mothers who have returned to work were more than twice as likely to be formula fed at 12 months (odds ratio 2.29; CI 95% (1.44-3.64). 2 | ATOPI C OUTCOME S Milk, egg and peanut introduction, sensitization and allergy in the CORAL group are summarised in Table 3 . Sensitization was defined as: a positive skin prick test (>3 mm, in the presence of a negative control of 0 mm to saline and a positive control of >3 mm to histamine) and/or evidence of food allergen-specific IgE (>0.35 kU A /L). Food allergy was diagnosed as evidence of IgE sensitization, as defined, and either a positive history of clinical reaction or a positive oral food challenge. Sensitization and allergy are compared between the CORAL and BASELINE cohorts at 12 months in Table 4 . We hypothesised that social restrictions imposed by the SARS-CoV-2 lockdown would result in altered infant microbiome and atopic outcomes through reduced encounters with 'old friend' microbes brought to the infant through family members, creche and sibling school attendance. However, changes in other related health factors, including reduced antibiotic use and increased breastfeeding, which may positively affect gut microbiome diversity were also noted in this cohort. At 12 months, less than half of CORAL babies had experienced any infective illness and just 17% had received a systemic antibiotic. Antibiotic consumption in the CORAL group at 12 months was in line with the lowest prescription rate, seen in Switzerland, in this study. Of note, the recently published EuroPrevall study demonstrated unexpectedly low prevalence of probable cow's milk and egg food allergy in Switzerland. 6 Ireland has the lowest breastfeeding rate in Europe. In 2015, the National Perinatal Reporting System recorded that only 58% of babies in the Republic of Ireland were receiving any breast milk on discharge from the maternity hospital after birth. 7 This falls significantly to 35% of babies receiving some breast milk at 3 months, 15% at 6 months and 11% at 9 months. 8 In the CORAL cohort, rates were markedly different with 192/354 (54%) of infants at 6 months and 121/344 (35%) of infants at 12 months still receiving breast milk. Maternal return to work has previously been associated with the discontinuation of breastfeeding. In a pre-pandemic Irish cohort 'Growing Up in Ireland', researchers identified mothers returning to part-time work were 30% more likely and those returning to fulltime work 113% more likely to quit breastfeeding. 8 These differences were noted in the CORAL cohort with higher formula use at 12 months in those who had returned to work. However, 29% of mothers who had returned to work were still breastfeeding at 12 months in the CORAL group, which is dramatically higher than pre-pandemic figures. This may reflect mothers who returned to work from home and due to convenience, access or privacy were able to continue breastfeeding. This dramatic and rapid change in There are limited recent epidemiological data on the current incidence of AD, especially in the first year of life. The AD incidence of 25.3% in the CORAL cohort may reflect a slow upward trend in AD since the national data set in 2008. However, it may also reflect more recent pandemic-related changes as outlined above. Food allergen introduction continued to improve from 6 to 12 months although 20% of infants had still not yet introduced peanut at 12 months despite early weaning advice. Egg sensitization was statistically significantly higher in the CORAL group, which may be a result of the higher incidence of AD. This higher incidence of sensitization has not translated into a higher incidence of egg allergy at 12 months when compared to the BASELINE cohort. This likely reflects the change in clinical practice regarding the graded reintroduction of baked egg in infants with a history of reaction to egg, which has led to tolerance by 12 months in most treated infants. 10 At 12 months, the CORAL cohort has higher rates of egg sensitization and AD, but not egg allergy, when compared to a national historic data set. Antibiotic use and infant illness and hospitalisation were much lower in this cohort, and breastfeeding rates were dramatically higher than pre-pandemic Irish figures. Microbiome analysis from 6-month and 12-month appointments is ongoing and may offer further explanation for the increased sensitization and AD seen in this cohort at 12 months in the context of other favourable factors including increased breastfeeding. allergic outcomes, birth cohort, SARS-CoV-2 This study received funding from Temple Street Hospital Foundation, Dublin, Ireland, and the Clemens Von Pirquet Foundation, Geneva, Switzerland. Allergy 2 (0.6) ** 1 (0.06) p = .03 ** *denotes p-value < .05; ** denoted p-value < .01. 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