Discussion
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 breast feeding, 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. 90%
of infants in a UK Birth cohort in 2008 had experienced an illness by 1
year and 80% had received a systemic antibiotic in the first year of
life. The low rates of infant illness and hospitalisation in CORAL
support the pre-study expectation of fewer viral infections circulating
due to lockdown restrictions. Fewer antibiotics likely reflects a
combination of fewer infections and less healthcare utilisation.
Powerful community based epidemiological data that supports our focused
prospective study has confirmed dramatically reduced admission rates for
paediatric respiratory and severe bacterial infections since March 2020
when compared with the preceding 3 years.
An analysis of antibiotic consumption in 5 European countries (Austria,
Italy, Germany, the Netherlands, Switzerland) identified antibiotic
usage between 17- 60% in the first year of life. 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. .
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 breastmilk on discharge from
the maternity hospital after birth. This falls significantly to 35% of
babies receiving some breastmilk at 3 months, 15% at 6 months and 11%
at 9 months. 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
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 full time
work 113% more likely to quit breastfeeding. 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
breastfeeding rates seen in this group of mothers may direct further
research into barriers to breastfeeding in Ireland.
Despite lower antibiotic use and higher breastfeeding rates our data
show AD incidence has increased in Irish infants. The AD incidence of
15.5% in the BASELINE cohort in 2008 is in keeping with incidence data
from the International Study of
Asthma and Allergies in Childhood (ISAAC) of between 15-20% in 2006.
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 dataset 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 sensitisation was statistically
significantly higher in the CORAL group which may be a result of the
higher incidence of AD. This higher incidence of sensitisation has not
translated into a higher incidence of egg allergy at 12 months when
compared with the BASELINE cohort. This likely reflects the change in
clinical practice regarding 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.