Prevalence of persistent Long COVID symptoms after SARS-CoV-2 infection

In a recent pre-print study posted to the medRxiv* pre-print server, a team of researchers assessed the prevalence, risk factors, severity, and impact on quality of life (QoL) of persisting coronavirus disease 2019 (COVID-19) symptoms in the first year after an individual is diagnosed with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

Study: Prevalence and determinants of persistent symptoms after infection with SARS-CoV-2: Protocol for an observational cohort study (LongCOVID-study). Image Credit: Starocean/ShutterstockStudy: Prevalence and determinants of persistent symptoms after infection with SARS-CoV-2: Protocol for an observational cohort study (LongCOVID-study). Image Credit: Starocean/Shutterstock


Of the over 308 million global confirmed cases of COVID-19 recorded by the end of 2021, 10-20% of cases have reported persistent symptoms for weeks and months following acute SARS-CoV-2 infection. Varying symptoms of COVID-19 infection were observed in patients from asymptomatic infection through to critical and chronic disease.

Despite most patients being able to fully recover from COVID-19, there is mounting evidence to prove that a significant number of individuals who have recovered from COVID-19 suffer from long-term complications or persisting symptoms. This recovery delay experienced by individuals in which they fail to regain their normal QoL after recovering from COVID-19 infection and suffer lasting effects of the infection long after the expected period of recovery is named “LongCOVID” or “post-COVID-19 condition”.

About the study

In the present study, the researchers aimed to analyze the prevalence and severity of persistent symptoms in the first year of COVID-19 infection as compared to non-infected individuals. They also studied the risk factors involved in post-COVID-19 condition cases.

Two groups consisting of prospective and retrospective data with one year of follow-up were studied in this research. The ‘prospective cohort’ included participants who had tested positive for SARS-CoV-2 infection in the last seven days, participants who had tested negative for SARS-CoV-2 infection in the last seven days, and a control group. The ‘retrospective cohort’ consisted of participants with self-reported persisting SARS-CoV-2 infection symptoms, with or without having had a positive test result, considered as post-COVID-19 condition cases.

At the beginning of the study, data on demographical characteristics such as gender, education level, and employment along with data on comorbidities were collected. Data regarding testing for SARS-CoV-2, COVID-19-related complaints, and vaccination data were collected at baseline and at three, six, nine, and 12 months since the beginning of the study.

Questionnaires were used to collect additional weekly data to analyze the health-related QoL (HRQoL) for individuals exhibiting SARS-CoV-2 infection symptoms in the first 8 weeks following a positive COVID-19 test. These questionnaires consisted of five dimensions of health, namely mobility, self-care, usual activities, pain/discomfort, and anxiety/ depression. Other parameters like fatigue severity, cognitive function, body pain, dyspnea, cognitive and emotional representations of illness, hospital anxiety and depression, absenteeism, unpaid productivity losses, and informal care were also determined.


Many previous studies have analyzed the prevalence of long-term symptoms and risk factors in populations including previously hospitalized patients, patients with diabetes type 1 and 2, in-home isolated patients with milder symptoms, and young individuals. Blomberg reported that 61% of patients reported persisting COVID-19 symptoms 6 months after the infection. These persisting symptoms comprised of loss of taste and/or smell, fatigue,

dyspnea, impaired concentration, and memory problems. Symptoms like fatigue, muscle weakness, sleep difficulties, and anxiety or depression were the most prevalent in a hospitalized population at the six-month time point.

This LongCOVID study determined the prevalence and risk factors of persistent symptoms of SARS-CoV-2 infection in LongCOVID cases. The study enabled the comparison of various control cohorts with similar experiences such as lockdown measures implemented in the wake of the COVID-19 pandemic. Population control groups allowed the researchers to control the background prevalence of SARS-CoV-2 infection symptoms. Furthermore, the test-negative controls allowed the control of other respiratory infections as compared to SARS-CoV-2 infection symptoms.

The assessment of symptoms at baseline and at the three aforementioned time points during one year of follow-up enabled the evaluation of the time course of symptoms and the detection of disabling symptoms at the three time intervals. The study also facilitated analysis of the impact of the post-COVID-19 condition on the general QoL.

The researchers concluded that the LongCOVID study can provide in-depth insights into the prevalence and severity of persistent symptoms after SARS CoV-2 infection. Better insights into persisting symptoms following a COVID-19 infection can allow better diagnosis, management, and may reduce the negative impact of the infection on HRQoL.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
Susha Cheriyedath

Written by

Susha Cheriyedath

Susha has a Bachelor of Science (B.Sc.) degree in Chemistry and Master of Science (M.Sc) degree in Biochemistry from the University of Calicut, India. She always had a keen interest in medical and health science. As part of her masters degree, she specialized in Biochemistry, with an emphasis on Microbiology, Physiology, Biotechnology, and Nutrition. In her spare time, she loves to cook up a storm in the kitchen with her super-messy baking experiments.


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