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Risk of serious COVID-19 outcomes among adults with asthma in Scotland: a national incident cohort study

January 2022: Research published in The Lancet Respiratory Medicine looks at which adults with asthma in Scotland might be at risk of serious complications from COVID-19.

Risk of serious COVID-19 outcomes among adults with asthma in Scotland: a national incident cohort study

Shi T, Pan J, Vasileiou E, et al.

Read the paper

Published Online January 13, 2022

Available via The Lancet Respiratory Medicine (online): https://doi.org/10.1016/S2213-2600(21)00543-9

Summary in Plain English

Towards the end of 2021, many countries around the world started to offer COVID-19 booster vaccines, particularly for people who are more likely to become very unwell from a coronavirus (SARS-CoV-2) infection.

The UK’s COVID-19 booster vaccine programme started in September 2021, with priority given to:

  • Care home residents
  • People aged over 40
  • Frontline health and social care workers
  • Adults who are clinically extremely vulnerable
  • People who have a suppressed immune system.

Pregnant women were included on this priority list from 16 December 2021.

Why did we carry out this research?

Asthma is a common condition in the UK. Several recent studies link poor asthma control in adults with a higher risk of serious COVID-19 complications. These include having to go to hospital, being admitted to intensive care, or dying from COVID-19.

However, there have not been any studies assessing these risks at different points during the pandemic for a national population. This includes taking into account a person’s vaccination status.

We wanted to understand whether:

  • Having asthma puts adults in Scotland at a higher risk serious COVID-19 complications
  • Particular groups of adults with asthma are at higher risk than others.

This knowledge will help to inform which adults with asthma should be prioritised for booster vaccines.

We carried out this study in response to a request for evidence from the Joint Committee on Vaccination and Immunisation (JCVI). The JCVI advises the UK Government on vaccines for COVID-19 and other diseases.

What data did we use?

We analysed health data records for all 4.4 million adults in Scotland, held securely in our EAVE II dataset, who were aged 18 or older as of 1 March 2020. This health data includes:

  • Prescriptions
  • Hospital admissions and death records
  • Information on age, sex, Body Mass Index (BMI) and location
  • Vaccination status
  • 28 other risk factors for COVID-19, aside from having asthma.

We studied the group from 1 March 2020 to 27 July 2021.

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In our study, we looked at adults who had been prescribed oral corticosteroids or admitted to hospital for asthma in the previous two years. Oral corticosteroids (commonly known as ‘steroid tablets’) for asthma include prednisolone, prednisone and dexamethasone.

NHS information on prednisolone

NHS information on dexamethasone

We defined hospital admission for COVID-19 as anyone admitted to hospital within 14 days of a positive PCR testor with COVID-19 listed as the reason for their admission. We defined COVID-19 deaths as anyone who died within 28 days of a positive PCR test, or with COVID-19 listed as a cause of death on their death certificate.

National Human Genome Research Institute: information on COVID-19 PCR tests

What did we find?

Of the 4.4million adults in this study, 12.7% had asthma diagnosed by a doctor. Of these 561,279 people, there were 39,253 (7.0%) with a confirmed SARS-CoV-2 infection in the study period.

Tracking the health of infected adults with asthma until 27 July 2021, we found that:

  • 4,828 people were admitted to hospital with COVID-19 (12.3%)
  • 1,600 people were admitted to intensive care with COVID-19 (4.1%)
  • 1,206 died of COVID-19 (3.1%).

We estimated that 600 of the 4,828 people in hospital (12.4%) may have been infected while in hospital for another reason.

In our analysis, the risk of a person having any serious complication from COVID-19 increased with the number of times they had been prescribed oral corticosteroids for asthma attacks in the previous two years.

We found that adults are more likely to have serious complications from COVID-19 if they have a recent history of treatment for asthma attacks. This is compared both to people without asthma, and people without a recent history. Here, a recent history of treatment includes people in the last two years who have either:

  • Been admitted to hospital for an asthma attack
  • Had two or more courses of oral corticosteroids for asthma.

We found that people with recent prescriptions of oral corticosteroids for asthma were more likely to be admitted to hospital during the third wave of the pandemic, when the Delta variant of SARS-CoV-2 was most common, than in the first wave.

Our data confirmed that having two doses of a vaccine greatly increases protection against COVID-19 hospitalisation, for people with and without asthma.

What does this mean?

In this study, we have shown that people who have recently been admitted to hospital or prescribed oral corticosteroids for asthma are more likely to be seriously unwell with, or die from, COVID-19.

Our data suggests that people with a recent history of asthma attacks who have needed hospital treatment or two or more courses of oral corticosteroids, should be prioritised for booster vaccines.

In Scotland, this would translate to 160,910 adults with asthma who may need to be prioritised for a COVID-19 booster. When scaled up across the UK, this would be approximately 1.9 million adults.

As the COVID-19 pandemic progresses, we will continue to monitor the risk of COVID-19 complications for different groups of people, and level of protection that vaccines offer as new variants emerge.


This plain English summary and infographic were created with the support and feedback of the EAVE II Patient Advisory Group (PAG). This article in particular was reviewed by PAG members Lynn L and Emily L.

To learn more visit : Our EAVE II Patient Advisory Group (PAG) | The University of Edinburgh