Due to the expected increase in long COVID cases, social consequences have to be considered in addition to the impairments in daily life for the affected persons and their families. The aim of the cooperation with the Belgian HTA institute, KCE, was to provide an overview of long COVID prevalences and possible risk factors, as well as of the consequences for everyday life.

A systematic search of 11 databases and a hand search were performed. Considering the predefined inclusion and exclusion criteria, 28 studies in 29 publications were included, comprising 22 cohort studies and six cross-sectional surveys.

Currently available data on the epidemiology of long COVID revealed that 5-36% of non-hospitalised COVID-19 patients and 39-72% of hospitalised patients reported long-lasting or recurrent symptoms one to three months after the acute infection. After three to six months, there was a slight decrease in prevalences in both patient populations (2-21% and 51-68%, respectively). After more than six months, 13-25% and up to 60% of the non-hospitalised and hospitalised patients respectively, still reported persistent symptoms. The most commonly reported symptoms among long COVID patients were fatigue (16-98%), shortness of breath (10-93%) and headache (9-91%) one to three months after acute infection, and fatigue (16-78%), cognitive impairment (13-55%) and respiratory problems (16-21%) after three to six months.

Furthermore, the studies suggested that the female gender and a high number of symptoms during the acute infection may favour the occurrence of long COVID symptoms. In addition, some long COVID patients experienced impairments in activities of daily living and reduced social participation (e.g. inability to work).

Until today, it remains unclear to what extent the reported long COVID symptoms can be distinguished from similar symptoms of other diseases and to what extent they are novel long-term symptoms (type and duration) compared with the long-term consequences of other severe infectious diseases. For this reason, sufficiently large, prospective, and, if possible, comparative cohort studies are recommended for future research initiatives. In addition, transparent communication of long COVID prevalences, including any potential uncertainties in the data, will be important in the future.