Asthma and COVID-19: risks and management considerations
May 28, 2020
On behalf of the Oxford COVID-19 Evidence Service Team
1. Nuffield Department of Primary Care Health Sciences, University of Oxford
2. Medical Sciences Division, University of Oxford
3. NIHR Newcastle In Vitro Diagnostics Co-operative, Newcastle University
4. Royal Brompton Hospital and Imperial College, London
5. Royal Hampshire County Hospital, Hampshire Hospitals Foundation Trust
6. University Hospital Southampton NHS Foundation Trust
Correspondence to email@example.com
It is unclear if people with asthma are at increased risk of contracting COVID-19 or of worse outcomes from COVID-19 infection. The evidence available is limited with some sources suggesting an underrepresentation of PWA in hospitalised cases, and others showing an increased risk of worse outcomes in PWA which may be associated with disease severity. Consensus broadly holds that asthma medications should be continued as usual. Asthma care may be disrupted during the pandemic; self-management and remote interventions may be of benefit but have not been tested in this context.
People with asthma (PWA) have been identified as being at increased risk of serious illness from COVID-19. Understanding this risk and best ways to mitigate it is key to enabling patients, carers, and healthcare professionals to make informed choices about ways to manage asthma during the COVID-19 pandemic.
This rapid review sets out to answer the following questions:
- Are PWA at increased risk of contracting COVID-19?
- Are PWA at increased risk of worse outcomes from COVID-19?
- Are PWA at risk from COVID-19 related disruptions to care?
- How should asthma be managed during the COVID-19 pandemic?
- How should PWA be managed when presenting with COVID-19?
Are PWA at increased risk of contracting COVID-19?
As community testing for COVID-19 is still limited, it is impossible to say with any certainty if any groups are more or less likely to contract the disease. Most data on disease prevalence and outcomes come from people hospitalised with COVID-19. At the outset of the pandemic, it was anticipated that people with respiratory diseases, including asthma, would be at higher risk, but emerging data are inconsistent.
In early data on COVID-19 cases (November to February), chronic pulmonary diseases including asthma were ‘surprisingly underrepresented’ (review). A narrative review published on 1st May 2020 noted that the prevalence of asthma in patients with COVID-19 may be lower than expected from population levels, based on both US data and data from China. It is speculated that this may be due to underdiagnosis, poor coding, different immune responses in those with asthma, differences in ACE2 expression, or a protective effect of inhaled corticosteroids. In a prospective observational cohort study of 166 UK hospitals (pre-print, n = 16,749) 14% of patients hospitalised with COVID-19 had asthma (the rate of asthma in the UK population is estimated to be 12%).The Canadian Thoracic Society have issued a position statement that there does not appear to be an increased risk for PWA to acquire COVID-19 infection. The British Thoracic Society states that it remains unclear whether asthma is a risk factor for COVID-19 and COVID-19 related complications. As COVID-19 disproportionately affects older people, the risk of COVID-19 in children with asthma is also unclear.
Data on outcomes in PWA from previous pandemics are also difficult to interpret. PWA appeared under-represented in a review of 473 cases of H1N1 hospitalisations during the 2009 influenza pandemic. In a cohort study (pre-print) from the US and South Korea comparing patients hospitalised with COVID-19 and those hospitalised with influenza from previous years, those hospitalised with COVID-19 had a lower prevalence of asthma compared to those hospitalised with influenza in the US data sources, but higher in the data from South Korea.
Are PWA at increased risk of worse outcomes from COVID-19?
It is unclear whether PWA in general are at increased risk, given the above data showing some instances of under-representation of PWA in those hospitalised with COVID-19. Others have noted it may be difficult to differentiate between COVID-19 symptoms and asthma exacerbations, and that beyond the direct risk of infection itself, there is also a risk of experiencing asthma exacerbations triggered by the virus.
Numerous bodies have identified people with moderate to severe asthma as being at increased risk: the Centers for Disease Control (CDC) state people with moderate to severe asthma are at increased risk of getting very sick from COVID-19; Asthma UK notes a PWA would be considered at very high risk if they were taking extra controller medicines as well as a preventer inhaler and continuous or frequent oral steroids; and the British Thoracic Society notes people taken biologic therapies for severe asthma are considered at very high risk.
A large English cohort study (pre-print, n = 17,425,445, published after previous review), found that asthma was associated with an increased risk of in-hospital death from COVID-19 in both age and sex adjusted and ‘fully adjusted’ (for co-morbidities) models, with risks higher in those with recent oral corticosteroid use (age and sex adjusted HR 1.70 (95% CI 1.48 to 1.96)) compared to those without recent use (age and sex adjusted HR 1.23 (95% CI 1.14 to 1.33). Corticosteroid use can be considered a proxy for disease severity in asthma, so it is unclear if corticosteroid use itself impacts risks from COVID-19 (this is reviewed elsewhere and discussed further below).
Are PWA at risk from COVID-19 related disruptions to care?
Pandemics and national emergencies pose risks to people with long-term conditions because of disruptions in care and disease management. This is reviewed elsewhere, and includes PWA. The possibility that access/adherence to asthma medications may be affected by the current pandemic has been highlighted as an area of concern; exacerbation events and subsequent need for hospitalisation could increase patient exposure to healthcare settings and hence increase risk of infection. A US review of management of asthma in children during the pandemic has noted that the impact of school closures on children with asthma remains to be seen, as schools often have a role in administering asthma medications, and as school closures are speculated to increase the risk of childhood obesity, which is a risk factor for worsening asthma.
How should asthma be managed during the COVID-19 pandemic?
The diagnosis of asthma is made from a combination of history, examination and supportive tests. Over time, guidelines have placed greater emphasis on objective tests in the diagnostic pathway; a diagnostic algorithm from NICE requires multiple tests to establish asthma diagnosis. These changes over time are important to reduce over- and under-diagnosis, and to look for overlap diseases, e.g. COPD.
This is likely to cause difficulties in the current pandemic. Association for Respiratory Technology and Physiology (ARTP) guidance suggests all respiratory testing is likely to be considered an aerosol generating procedure (AGP) due to its potential to generate coughing, and to assume all patients may have COVID-19. As such, full personal protective equipment (PPE) needs to be worn, with appropriate infection control/air changes.
The capacity to perform testing will be vastly reduced, due to the above measures, combined with reduced staff availability, backlog of tests which have arisen, and ARTP guidance that testing should no longer occur in routine primary care practice (unless part of a coordinated hub). Consultations will also be performed virtually to a much greater degree. It is likely that this will lead to misdiagnosis, forcing clinicians to rely to on history alone to a much greater degree than they would have otherwise.
Asthma control and monitoring
Asthma UK, the Asthma and Allergy Foundation of America, the British Thoracic Society, and the Canadian Thoracic Society, among others, suggest people manage their asthma as well as possible to reduce risk from COVID-19. Suggestions include the following for PWA:
Peak expiratory flow rate (PEFR) can generate a cough and hence become an aerosol-generating procedure (AGP). RCEM guidance in acute exacerbations is only to perform after nebulisation, in those cases where discharge is considered. As mentioned above, ARTP guidance suggests all respiratory testing should be considered an AGP. We did not find any guidance on measurement of exhaled nitric oxide (FeNO).
Multiple questionnaires have been developed to help clinicians in monitoring asthma and related comorbidities, such as the Royal College of Physicians 3 questions, ACQ, ACT, amongst many others. Some of these are more readily available online than others, in part to prevent mis-use where the format of the questionnaire has been mis-transcribed. Patients may lack technical skills/resources to access online even where available, necessitating postal of questionnaires (which may lead to non-return/missing data), or verbal/virtual ‘run-throughs’ of the questionnaires (which may not have been validated for the questionnaire involved).
All sources reviewed (including NICE in the UK and the CDC in the US) agreed that, on the whole, medications for asthma should continue to be taken as normal. This includes biologics. Prednisone is recommended for treating severe asthma exacerbations.
There is mixed advice on nebulisers with NICE guidance encouraging continued use, a position supported by Public Health England and Health Protection Scotland. A narrative review of managing asthma in children during the pandemic suggests that in most cases children should be switched to other inhaler types, but it is unclear what this advice is based on, a broader narrative review makes the same recommendation, and the Canadian Thoracic Society also warns against their use in certain settings. Concerns with nebulisers relate to the possibility of the devices of aerosolizing the virus if the PWA using the device is infected, therefore increasing risk of contagion. NICE states this is not a concern “because the aerosol comes from the fluid in the nebuliser chamber and will not carry virus particles from the patient”; the British Thoracic Society echoes this. In acute asthma exacerbations, the Royal College of Emergency Medicine (RCEM) suggests consideration of usage of metered dose inhalers (MDI)/spacer for mild/moderate exacerbations, rather than nebulisation, and where nebulisation is used, using minimal flow rate of oxygen required to drive the nebuliser.
Though there has been some debate over the use of inhaled corticosteroids during the COVID-19 pandemic, there is general consensus that their use should not be discontinued (and little evidence of a benefit from introducing them in people in the acute phase of the virus who do not otherwise use them). Some evidence suggests inhaled corticosteroids may be of use in treating COVID-19 but this is currently unclear.
Smartinhalers are in development for asthma and COPD; the early evidence is mixed, but they may allow remote monitoring of compliance.
Asthma UK have noted that some PWA have reported issues with accessing medications and suggest if pharmacists can’t provide or source alternative patients ring around other pharmacies or get in touch with their GP. To avoid possible supply issues, NICE recommends medications be prescribed for no more than 30 days; the CDC recommends 30 day supplies of non-prescription medications and supplies.
Asthma UK states people should still be getting their same asthma care but some elements “might look different” (i.e. be delivered remotely). They suggest emergency care proceed as normal, GP and specialist care will most likely be via remote means or postponed, and some annual asthma reviews will be postponed.
NICE have issued rapid guidance on severe asthma during the COVID-19 pandemic. Recommendations include:
- Communicating with patients and minimising risk by decreasing face-to-face contact where possible
- Only carrying out bronchoscopy and most pulmonary function tests for urgent cases where results will have a direct impact on patient care (as these tests may spread COVID-19)
- Use of continued and new medications where necessary, with consideration given to training to self-administer and remote monitoring
- Advising PWA not to share inhalers or devices and to wash their hands and clean equipment regularly
- Local policies to address modifying usual care at organisational level.
A reduction in face-to-face appointments is common across countries experiencing COVID-19 pandemics, which will affect asthma care (as already discussed briefly above). Remote care is increasingly being used, but in studies in PWA, remote care is often tested in addition as opposed to instead of face-to-face contact with healthcare providers (HCPs).
In adults, a 2019 systematic review and meta-analysis of telemedicine for asthma (22 studies, 10,281 participants) found tele-case management could significantly improve asthma control compared with usual care (SMD 0.78, 95% CI 0.56 to 1.01). A 2011 systematic review and meta-analysis of telehealth interventions involving healthcare providers (HCPs) in the care of PWA (21 RCTs) did not find clinically important improvements in quality of life or number of visits to the emergency department over 12 months, but did find a significant reduction in the number of patients admitted to hospital once or more over 12 months. The authors concluded telehealth was no better or worse than normal care. This is consistent with a 2016 Cochrane review which found no important differences between face-to-face and remote asthma check-ups in terms of asthma outcomes; however, a lack of information and wide confidence intervals meant the authors could not rule out clinically important differences. A 2015 systematic review found telemedicine interventions did not appear to improve asthma function scores, but concluded “other benefits may be present.” It has been speculated that telehealthcare interventions may be more likely to result in significant benefit in people with severe disease compared to those with relatively mild asthma.
In children and young people, a systematic review (15 studies) found personalised text messaging was the most commonly used digital intervention for asthma care, and that nearly all of the included interventions significantly improved adherence; most also improved health outcomes. In contrast, another systematic review found mixed results for telemedicine in school-aged children, with no evidence of harm, but some studies finding no effect and others finding improvements in health outcomes and adherence. A 2018 review found eHealth tools may be particularly useful for self-monitoring in children and adolescents with asthma.
None of the studies were conducted in the context of reduced healthcare capacity so their relevance to the current pandemic context is unclear.
Recommendations that people manage asthma as well as possible during the pandemic may be more challenging due to disruptions posed by the pandemic. A systematic review of 56 studies found the most common themes relating to barriers to asthma self-management included mood disorders and anxiety, social support, and access to healthcare, all of which may be disrupted in the current context.
Self-management and self-education interventions may play a role in asthma control in the context of diminished access to healthcare providers. A 2014 systematic review and meta-analysis of interventions targeting asthma self care in adults (38 trials, 7883 participants) found that interventions targeting asthma self-care reduced symptoms (standardized mean difference −0.38, 95% CI −0.52, −0.24) and unscheduled health care use (odds ratio (OR) 0.71, 95% CI 0.56 to 0.90) and increased adherence to preventive medication (OR 2.55, 95% CI 2.11 to 3.10). The authors were unable to identify what the optimal components of these interventions were, though active involvement of participants was associated with increased effectiveness. Educational programmes have also been found to be effective in children and adolescents (2003 review; 2008 review). A meta-review speculated that digital interventions for asthma may have benefits for people under the age of 65. A separate systematic review concluded that culturally tailored online asthma self-management programmes show promise in difficult-to-reach populations.
A 2018 systematic review found that mobile health interventions for asthma self-management improved asthma control and medication adherence compared to routine care, but results across reviews are mixed. A 2017 systematic review and meta-analysis found that mobile applications improved asthma control (3 studies) but that overall clinical effectiveness varied; authors were unable to identify which components contributed to effectiveness. A 2013 Cochrane review found inconclusive results. A 2018 review found limited evidence that mobile phone apps had a positive effect on asthma self-management in adolescents.
Self-care interventions which have shown promise for asthma control also include decreasing exposure to allergens and pollutants (systematic review, noted general issues with study quality). Systematic reviews differ regarding the effectiveness of air filtration systems, with one finding a positive effect and another not detecting an effect (the included trials were very small). Weight loss in PWA with overweight or obesity may also improve asthma control (systematic review in adults, 10 RCTs; systematic review in adults and children; though issues with the evidence have been noted); obesity has also been identified as a risk factor for COVID-19 severity. Physical activity has been linked with better asthma control, in both children and adults; in people with stable asthma, physical activity interventions of at least 20 minutes, twice a week did not seem to exacerbate symptoms.
Most evidence on self-management in asthma comes from interventions that also involve support from HCPs; though this evidence is broadly positive in showing some benefits and no evidence of harms, it’s relevance to the current pandemic context is unclear. A 2015 review found that, to increase the value of self-management plans in asthma, patients, professionals and organisations all needed to be targeted.
As noted above, mood disorders and anxiety are barriers to effective asthma control (systematic review). People with asthma have a higher prevalence of anxiety and depression than the general population, which is associated with poorer asthma control, medication adherence, and health outcomes. The pandemic has the potential to exacerbate existing and introduce new mental health issues, with the potential of profound impacts on wellbeing. To manage this, Asthma UK recommends PWA stay active, look after their physical health, stay social, and request support. Several systematic reviews have suggested yoga may improve quality of life in asthma but evidence here is very limited (2016 Cochrane review; 2011 review). Systematic reviews of cognitive behavioural therapy (CBT) in both adults and children found CBT may improve mental health outcomes in PWA, but there were issues with study quality. Systematic reviews have found generally low quality evidence (due to issues with study quality and heterogeneity) for mindfulness-based stress reduction interventions, written emotional disclosure interventions, and relaxation-based therapies in improving wellbeing in PWA, including in both adults and children. In-person psychological therapies will be difficult to access at the current time.
How should PWA be managed when presenting with COVID-19?
Asthma UK provides guidance for what to do for PWA who suspect they may have COVID-19. Considerations specific to PWA include:
- If you get an asthma cough and are not sure whether your cough is a symptom of COVID-19 or related to your asthma, talk to a healthcare provider (the British Thoracic Society suggests HCPs let patients know that it is uncommon to get a high temperature, tiredness, and changes in taste or smell with an asthma attack so presence of those symptoms are more likely to suggest COVID-19 infection)
- Keep following asthma action plan
- Carry on taking all asthma medications as usual
- Call 999 for an ambulance if having an asthma attack, and tell them you have COVID-19 symptoms.
A narrative review from the US notes that in early stages there is overlap with asthma and COVID-19 symptoms that only later may progress to more clearly defined COVID-19 symptoms; the same group presents an algorithm suggesting when face-to-face (as opposed to telehealth) evaluation is needed based on COVID risk (high/low) and asthma severity (high/low) or uncertain diagnosis.
There is some advice circulating that ambulance services are advising when assessing PEFR in suspected COVID in PWA in their own home, crews should be at least six feet away and ideally in another room.
For hospitalised patients, a review article presents strategies for aerosol drug delivery to reduce infection risk, and the British Thoracic Society suggests the SPACES approach for delivering ward care (based on the principles of “maximum patient contact – minimum staff exposure”).
- It is unclear if people with asthma are at increased risk of contracting COVID-19 or of worse outcomes from COVID-19 infection. The evidence available is limited with some sources suggesting an underrepresentation of PWA in hospitalised cases, and others showing an increased risk of worse outcomes in PWA which may be associated with disease severity.
- Consensus broadly holds that asthma medications should be continued as usual.
- Asthma care may be disrupted during the pandemic, self-management and remote interventions may be of benefit but have largely not been tested in this context.
- More research is needed on the possible associations between asthma and COVID-19 infection and severity.
- More research is also needed on interventions to support asthma care in light of current constraints and disruptions to healthcare systems.
Disclaimer: the article has not been peer-reviewed; it should not replace individual clinical judgement and the sources cited should be checked. The views expressed in this commentary represent the views of the authors and not necessarily those of the host institution, the NHS, the NIHR, or the Department of Health and Social Care. The views are not a substitute for professional medical advice.
Jamie Hartmann-Boyce is a departmental lecturer and deputy-director of the Evidence-Based Health Care DPhil programme within the Centre for Evidence-Based Medicine in the Nuffield Department of Primary Care Health Sciences, University of Oxford.
Afolarin Otunla is a 5th year medical student at Green Templeton College, Oxford.
Jonathan Drake is a 5th year medical student at St Catherine’s College, Oxford.
Jana Suklan is a IVD methodologist at the NIHR Newcastle In Vitro Diagnostics Co-operative Newcastle University, Newcastle.
Ella Schofield is a 5th year medical student at Worcester College, Oxford.
Jade Kinton is a 4th year medical student at Exeter College, Oxford.
James Gunnell is a 5th year medical student at Green Templeton College,Oxford.
Andrew Menzies-Gow is Director of the Lung Division, Royal Brompton Hospital, Professor of Practice (Respiratory Medicine), Imperial College, and National Clinical Director for Respiratory Services, NHS England & Improvement.
Matt Indada-Kim is an Acute Medicine Consultant at the Royal Hampshire County Hospital, Hampshire Hospitals Foundation Trust. He is also Clinical Lead for Sepsis/Deterioration for Wessex Patient Safety Collaborative and National Clinical Advisor on Sepsis and Deterioration.
Richard Hobbs is a GP and Nuffield Professor of Primary Care Health Sciences, Director, NIHR English School for Primary Care Research and Director, NIHR Applied Research Collaboration (NIHR ARC) Oxford.
Paddy Dennison is a consultant in respiratory and general internal medicine, Southampton General Hospital.
With thanks to Nia Roberts, subject librarian.
|((asthma*[Title/Abstract]) OR (“Asthma”[Mesh])) AND ((coronavirus*[Title] OR coronovirus*[Title] OR coronoravirus*[Title] OR coronaravirus*[Title] OR corono-virus*[Title] OR corona-virus*[Title] OR “Coronavirus”[Mesh] OR “Coronavirus Infections”[Mesh] OR “Wuhan coronavirus” [Supplementary Concept] OR “Severe Acute Respiratory Syndrome Coronavirus 2″[Supplementary Concept] OR COVID-19[All Fields] OR CORVID-19[All Fields] OR “2019nCoV”[All Fields] OR “2019-nCoV”[All Fields] OR WN-CoV[All Fields] OR nCoV[All Fields] OR “SARS-CoV-2”[All Fields] OR HCoV-19[All Fields] OR “novel coronavirus”[All Fields]))
|((influenza[Title/Abstract] OR pneumonia[Title/Abstract] OR SARS[Title/Abstract] OR MERS[Title/Abstract] OR severe respiratory infection*[Title/Abstract] OR acute respiratory infection*[Title/Abstract] OR “acute respiratory distress”[Title/Abstract] OR “severe respiratory distress”[Title/Abstract]) OR ((((“Middle East Respiratory Syndrome Coronavirus”[Mesh]) OR “SARS Virus”[Mesh]) OR “Influenza, Human”[Mesh]) OR “Pneumonia”[Mesh])) AND ((asthma*[Title/Abstract]) OR (“Asthma”[Mesh]))
|(SARS[Title/Abstract] OR MERS[Title/Abstract] OR severe respiratory infection*[Title/Abstract] OR acute respiratory infection*[Title/Abstract] OR “acute respiratory distress”[Title/Abstract] OR “severe respiratory distress”[Title/Abstract] OR “Middle East Respiratory Syndrome Coronavirus”[Mesh] OR “SARS Virus”[Mesh]) AND ((asthma*[Title]) OR (“Asthma”[Mesh]))
|(“Asthma/psychology”[Mesh]) OR (((asthma*[Title/Abstract]) OR (“Asthma”[Mesh])) AND (((((“Anxiety”[Mesh] OR “Anxiety Disorders”[Mesh]) OR “Stress, Psychological”[Mesh]) OR “Mental Health”[Mesh]) OR “Mental Disorders”[Mesh:NoExp]) OR (((((anxiety[Title]) OR (anxious[Title])) OR (anxieties[Title])) OR (stress*[Title])) OR (distress*[Title]))))
|((asthma*[Title/Abstract]) OR (“Asthma”[Mesh])) AND (((“Self-Management”[Mesh]) OR “Self Care”[Mesh:NoExp]) OR (self-manag*[Title/Abstract] OR selfmanag*[Title/Abstract] OR “self care”[Title/Abstract] OR self-monitor*[Title/Abstract] OR selfmonitor*[Title/Abstract]))
|((asthma*[Title/Abstract]) OR (“Asthma”[Mesh])) AND ((“Telemedicine”[Mesh]) OR ((telehealth[Title/Abstract] OR tele-health[Title/Abstract] OR telemedicine[Title/Abstract] OR tele-medicine[Title/Abstract] OR telerehab*[Title/Abstract] OR tele-rehab*[Title/Abstract] OR ehealth[Title/Abstract] OR “electronic health”[Title/Abstract] OR mhealth[Title/Abstract] OR “mobile health”[Title/Abstract]) OR (digital*[Title] OR internet*[Title] OR web*[Title] OR electronic*[Title] OR technolog*[Title])))
|((asthma*[Title/Abstract]) OR (“Asthma”[Mesh])) AND (((((((“Exercise Therapy”[Mesh]) OR “Exercise”[Mesh]) OR “Diet”[Mesh]) OR ( “Healthy Lifestyle”[Mesh] OR “Sedentary Behavior”[Mesh] OR “Risk Reduction Behavior”[Mesh] )) OR (exercise[Title] OR “physical activity”[Title] OR diet*[Title] OR nutrition*[Title] OR lifestyle[Title] OR “life style”[Title])) OR ((risk[Title]) AND (chang*[Title] OR modif*[Title] OR reduc*[Title] OR decreas*[Title]))) OR ((behav*[Title]) AND (chang*[Title] OR modif*[Title] OR reduc*[Title] OR decreas*[Title])))
|(((asthma*[Title/Abstract]) OR (“Asthma”[Mesh])) AND ((influenza[Title/Abstract] OR pneumonia[Title/Abstract] OR SARS[Title/Abstract] OR MERS[Title/Abstract] OR severe respiratory infection*[Title/Abstract] OR acute respiratory infection*[Title/Abstract] OR “acute respiratory distress”[Title/Abstract] OR “severe respiratory distress”[Title/Abstract]) OR ((((“Middle East Respiratory Syndrome Coronavirus”[Mesh]) OR “SARS Virus”[Mesh]) OR “Influenza, Human”[Mesh]) OR “Pneumonia”[Mesh]))) AND (((((((“Exercise Therapy”[Mesh]) OR “Exercise”[Mesh]) OR “Diet”[Mesh]) OR ( “Healthy Lifestyle”[Mesh] OR “Sedentary Behavior”[Mesh] OR “Risk Reduction Behavior”[Mesh] )) OR (exercise[Title] OR “physical activity”[Title] OR diet*[Title] OR nutrition*[Title] OR lifestyle[Title] OR “life style”[Title])) OR ((risk[Title]) AND (chang*[Title] OR modif*[Title] OR reduc*[Title] OR decreas*[Title]))) OR ((behav*[Title]) AND (chang*[Title] OR modif*[Title] OR reduc*[Title] OR decreas*[Title])))
|“(coronavirus OR covid-19) AND asthma*”
|(coronavirus OR covid-19) AND asthma
||TRIP, Google & Google Scholar
|((“Asthma”[Mesh]) OR (asthma*[Title/Abstract])) AND (inhaler*[Title]) Filters: Systematic Reviews
|((“Asthma”[Mesh]) OR (asthma*[Title/Abstract])) AND (action plan*[Title/Abstract] OR asthma plan*[Title/Abstract] OR treatment plan*[Title/Abstract]) Filters: Meta-Analysis, Systematic Reviews
References are linked to from the text