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Corona-infected persons who are not admitted to hospital for COVID-19 have a low risk of severe late complications

Researchers have systematically followed corona-infected persons’ contact with the healthcare system over a period of six months after infection. The findings show that infected people who have not been in need of hospitalisation have a low risk of severe late complications that require treatment with drugs or hospitalisation.

The study includes 8,983 Danes who tested positive for COVID-19 in the period from 27 February to 30 May 2020 and has compared them with 80,894 Danes who tested negative for COVID-19 in the same period. 

The study was conducted by examining data from the Danish health registers for hospital contacts and diagnoses, redemption of prescription medicine and visits to general practitioners.

- Until now, most studies that have examined complications post-corona infection have focused on patients who have been so ill that they have been hospitalised. The reality, however, is that the majority of infected people fortunately do not need to be admitted to hospital, says Anton Pottegård, senior author of the study and Professor at the University of Southern Denmark.


Does not rule out unpleasant late complications 

- Whereas previous studies of inpatients with COVID-19 describe a markedly increased risk of a number of severe late complications, such as blood clots, inflammation of the cardiac muscle, permanent impaired lung function and severe mental illness, our study shows that if you have had a mild bout of corona, your risk of severe complications leading to specific hospitalisations or treatment with drugs is small, Anton Pottegård adds.

The new study has just been published in The Lancet Infectious Diseases journal. 

- Among people who are not primarily admitted to hospital for COVID-19, we can see that the after-effects are limited when taking treatment with new drugs and late hospitalisations into account. However, this in no way precludes people from experiencing late effects in the form of, for example, headaches, fatigue and difficulty in breathing, but fortunately we do not see signs of an increased incidence of severe acute problems and new-onset chronic illness compared to people who have tested negative and not been infected with coronavirus.

For Anton Pottegård, the results of the new study are really good news.


Mild course of illness equals few severe late complications

- The results of the study are in line with my experience from the clinic, namely that the majority of COVID-19 patients with mild courses of illness usually get through the infection well without late complications, says Professor Henrik Nielsen from the Department of Infectious Diseases, Aalborg University Hospital, and co-author of the study.

He looks forward to the results of a number of ongoing Danish studies that seek to shed light on the extent and nature of late complications that may be present without triggering a visit to one’s GP or pharmacy. The factors that determine whether COVID-19 patients develop late complications are not yet known.


Reassuring result, but possible signal

- Late complications such as headaches, shortness of breath and fatigue can also be extremely problematic, but it is reassuring that when we systematically follow people who have been infected with coronavirus but not hospitalised because of it, we do not see any high incidence of for example, late hospitalisations due to blood clots or other severe late complications, says co-author of the study, Chief Physician Reimar W. Thomsen from the Department of Clinical Epidemiology, Aarhus University and University Hospital.

However, the study also shows that in the months following infection, people infected with coronavirus have 20% more contact with general practitioners than non-infected people. People infected with coronavirus also had a slightly increased risk of starting asthma medication or migraine medication, and a slightly increased risk of late diagnoses with shortness of breath, although their overall risk was low.

According to Reimar W. Thomsen, this may indicate more diffuse symptoms such as fatigue, headaches, muscle aches and shortness of breath, which are not always immediately treated with prescription medicine, but which often lead to contact with one’s GP.

Meet the professor

Anton Pottegård, Professor at the University of Southern Denmark



  • The study was carried out in collaboration between the University of Southern Denmark, Aalborg University, Statens Serum Institut, the University of Copenhagen, the Danish Medicines Agency and Aarhus University & University Hospital. 
  • 2,757 (31%) out of 8,983 corona-infected persons without primary need for hospitalisation started treatment with a new drug within 6 months. [No increase compared to the reference group of test-negative persons]
  • 121 (1.8%) out of 6,782 people started treatment with asthma medication for the first time to relieve shortness of breath. [Increase of 1.3x compared to the reference group]
  • 2,363 (26%) out of 8,983 corona-infected persons without primary need for hospitalisation had hospital contact with a new diagnosis within 6 months. [No increase compared to the reference group]
  • 103 (1.2%) out of 8,676 corona-infected persons were first diagnosed with shortness of breath within 2 weeks to 6 months after a positive test for coronavirus. [Increase of 2x compared to the reference group] 
Editing was completed: 11.05.2021