A recent study published in the British Medical Journal evaluated long-term symptoms and outcomes associated with post-coronavirus disease 2019 (COVID-19) condition.

Around 20% to 30% of non-vaccinated individuals suffer from the post-COVID-19 condition. Multiple studies investigating the long-term outcomes of the post-COVID-19 condition have reported that 22% to 75% of affected individuals experienced symptoms longer than one year after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

Many such studies comprised specific populations, focused on certain dimensions of the condition, and did not include a prospective follow-up. Moreover, their generalizability could be limited across the spectrum of COVID-19 severity. As such, limited knowledge and the lack of consensus on the core outcome set of the post-COVID-19 condition have resulted in using different outcome measures in observational studies, impacting their comparability.

Study: Recovery and symptom trajectories up to two years after SARS-CoV-2 infection: population based, longitudinal cohort study. Image Credit: p.ill.i / ShutterstockStudy: Recovery and symptom trajectories up to two years after SARS-CoV-2 infection: population based, longitudinal cohort study. Image Credit: p.ill.i / Shutterstock

Table of Contents

About the study

The present study comprehensively characterized the post-COVID-19 condition in the longitudinal population-based Zurich SARS-CoV-2 cohort. Adult residents of the Zurich canton, Switzerland, were eligible if they could follow study protocols. Subjects with a confirmed SARS-CoV-2 infection diagnosis between August 6, 2020, and January 19, 2021, were recruited. The comparator group included participants from another study without SARS-CoV-2 infection.

Data obtained from questionnaires were used for analysis. At baseline, the questionnaire captured data on sociodemographics, comorbidities, pre-infection health status, and acute infection. Follow-up questionnaires were administered at multiple time points after infection, which collected information on symptoms and mental and physical health.

The primary outcome was the relative health status at 6, 12, 18, and 24 months post-infection. The outcome was defined using self-reported recovery status and overall health status. Secondary outcomes were the prevalence and severity of symptoms. Self-perceived severity was evaluated using a five-point Likert scale and stratified into mild, moderate, and severe categories. Further, the team assessed the trajectories of symptoms and relative health status between six and 24 months.

Additional scale-based assessments were used to investigate adverse outcomes, such as fatigue, dyspnea, depression, anxiety, stress, and quality of life. Data after reinfection were not considered for analysis. The point prevalence and severity of symptoms and the relative health status were descriptively evaluated at follow-up. The characteristics of participants with different trajectories were compared. The excess risk of symptoms and adverse outcomes was assessed at six months.


Overall, 1106 individuals participated in the Zurich SARS-CoV-2 cohort. Of these, 788 completed the assessment at 24 months, and 776 completed all questionnaires between six and 24 months. Most participants were symptomatic (86%) during acute COVID-19 and 4.3% required hospitalization. Around 51.2% of participants were females, and 55.2% returned to normal health status in less than one month post-infection. However, nearly 23% of participants did not recover by six months post-infection.

Mild, moderate, and severe health impairment was observed in 16.2%, 3.6%, and 2.7% of participants, respectively. The proportion of participants reporting non-recovery declined over time and was 18.5% at 12 months and 17.2% at 24 months. More than 68% of participants reported continued recovery over time. By 24 months, 13.5% had improved or recovered, 5.2% had worsened health status, and 4.4% had stable health impairment. 

The prevalence of symptoms was similar at follow-up time points at around 51%. However, the prevalence of COVID-19-related symptoms declined from about 29% at six months to 18.1% at 24 months. Notably, most participants with COVID-19-related symptoms reported non-recovery at 24 months. The common symptoms were fatigue, dyspnea, post-exertional malaise, poor concentration or memory, and altered smell or taste.

The proportion of participants with adverse outcomes on scale-based assessments increased shortly after the infection and decreased from one month onwards. By 24 months, the proportion of participants with fatigue, dyspnea, depression, anxiety, and stress was 36.8%, 23.4%, 12.5%, 11.7%, and 7%, respectively. The prevalence of any symptom was higher in the Zurich SARS-CoV-2 cohort compared to non-infected subjects in the comparator group.

The excess risks among infected subjects relative to non-infected participants were the highest for altered smell or taste, post-exertional malaise, reduced memory or concentration, dyspnea, and fatigue. Further, more infected participants had anxiety symptoms at six months than non-infected subjects. There were no differences in the proportions of subjects with stress, depression, or other adverse outcomes.


In sum, around 18% of subjects infected with SARS-CoV-2 reported post-COVID-19 symptoms, and 17% did not attain their normal health status by 24 months after infection. Although many subjects recovered or improved over time, some had worsened health status or alternating courses. In addition, there was strong evidence that infected individuals had an excess risk of symptoms than non-infected subjects.

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