Atopic Dermatitis (AD, also known as atopic eczema and eczema) is a common disease affecting 20% of children in the UK and other high-income countries. The major genetic risk factor for AD is loss of function mutations in filaggrin, a critical skin barrier protein. There are many theories around the high prevalence of filaggrin mutations in European and Asian populations and of eczema including some proposals that having a leaky skin barrier and an overactive skin immune system might lead to skin immune cells being activated through the skin resulting in protection against pandemics. The COVID-19 pandemic is associated with substantial COVID-related health problems and deaths.

We will use data from the Avon Longitudinal Study of Parents and Children (ALSPAC) prospective birth cohort study questionnaires and clinical visits to identify people with evidence of eczema in childhood, and genetic data to identify people with filaggrin null mutations. We are very familiar with these data in ALSPAC and have very recently analysed these data. We will then determine if people in early adulthood (the age of the cohort at the time of pandemic emergence) with evidence of childhood eczema are at reduced risk of reporting symptoms suggestive of COVID-19. The subsequent analysis will involve assessing if those with filaggrin null mutations (with and without eczema) have reduced risk of reporting COVID-19 symptoms. We will stratify by the presence or absence of asthma to see if the risks vary in these subgroups.