Someone asked me about this relation. As you will see, the first paper, based on rather low quality data, failed to provide an unambiguous answer, but two large cohort studies in UK and Korea clearly established a relation mainly between non-allergic asthma and COVID severity, while the relation with various aspects of allergy is much weaker or non-existing. These observations certainly do not substantiate early speculations about “Th2” pathogenic mechanisms in COVID.
- A literature review in June by Morais-Almeida (Int Arch Allergy and Imunolog) found no clear indication of an association between asthma (or even COPD) and COVID-19 severity in Chinese and continental European series from the “first wave”, while the was emerging evidence of this association in the US and the UK. However, most of these studies were rather retrospective and based on rather small sample size, with no clear control group.
- A comprehensive study, based in the very large British Biobank by Zhu (J Allergy Clin Immunol June 2020) has clear-cut results:
- Adults with asthma had a higher risk of severe COVID-19, which was driven by the increased risk in patients with nonallergic asthma.
- In contrast, the risk of severe COVID-19 was not significantly elevated in patients with allergic asthma.
- In addition, the study demonstrated the absence of association between the existing genetic polygenic score for asthma and COVID-19
- A nation-wide Korean cohort study (Yang J Allergy Clin Immunol Sept 2020) is in the same line:
- Non-allergic asthma was associated with a slightly elevated risk of testing positivity for SARS-CoV-2 (OR 1.43), but a much higher risk on severe COVID (OR 4.09).
- In allergic asthma there was a trend for more severe COVID (OR 1.4), but is was NS
- Remarkably allergic rhinitis came with a slightly but significantly increased chance of testing positive (OR 1.2) and of having severe COVID (OR 1.4).
- There was no such trend for atopic dermatitis.
- A very large multi-continental study on the impact of COVID-19 on pediatric asthma (Papadopoulos J Allergy and Clin Immunol Sept 2020) comes with positive conclusions:
- Children with asthma do not appear to be disproportionately affected by COVID-19.
- Outcomes may even have improved, possibly through increased adherence and/or reduced exposures.
- Clinical services have rapidly responded to the pandemic by limiting and replacing physical appointments with virtual encounters.