We have in fact adopted the WHO definition of post-COVID-19 condition, which was used in the first study conducted in early 2022, in order to compare the situation in France before and after the major waves of SARS-CoV-2 infection linked to the Omicron variant. To compare our results with those obtained in the United Kingdom and the United States, we have also used the definitions from those two countries. In addition, to assess the burden of long COVID more accurately, we distinguished several forms of post-COVID-19 condition based on the level of impact (high, moderate, no impact) of the selected symptoms on activities of daily living. Finally, we asked survey participants whether they “believed they had been affected by a long-term form of COVID-19” (reported long COVID or perceived long COVID).

The agreement between the classifications derived from the different definitions was weak or moderate, with Kappa coefficients (ranging from 0, indicating agreement due to chance alone, to 1, indicating perfect agreement) ranging from 0.18 to 0.59. For example, 47% and 29% of people who met the criteria for the American (National Center for Health Statistics, US-NCHS) and English (Office for National Statistics, UK-ONS) definitions also met the WHO definition of post-COVID-19 condition. Similarly, less than half (43%) of people meeting the WHO’s definition believed they had been affected by long COVID. These discrepancies, which affected both sexes and all age groups, led us to present prevalence estimates according to the different definitions used to date in population-based studies. The WHO’s definition of post-COVID-19 condition offers the advantage of distinguishing between different levels of impact of symptoms on daily activities.

The prevalence of post-COVID-19 condition, as defined by the WHO, has been estimated at 4.0% of the French adult population, and at 2.4% and 1.2%, respectively, when considering cases with moderate and high impacts on people’s daily lives. Among people with post-COVID-19 conditions, 31% had been experiencing symptoms for more than twelve months, and 22% for more than eighteen months. In addition, the reported prevalence of long COVID was 7.1%, and 7.6% and 13.4% for the American and British definitions, respectively.
It was higher among women (5.4%) and lower among the elderly (2.2% for those over 65 and 1.7% for those over 75) and people living alone (2.5%). These differences were observed for all definitions used. They mainly reflect higher exposure to SARS-CoV-2 among women and lower exposure among the elderly and people living alone.

Among people whose SARS-CoV-2 infection occurred at least three months prior, the prevalence of post-COVID-19 conditions according to the WHO definition was 8%, ranging from 5.3% (men) to 10.2% (women), 14.9% (job seekers), and 18.6% (after hospitalization for COVID-19); 21% of these people had been infected during the Delta wave and 53% during the Omicron waves.
While the prevalence of post-COVID-19 condition remained at 4% in the general population between the beginning and end of 2022, the prevalence of post-COVID-19 condition calculated among participants who reported at least one infection in that year fell sharply: from 30% observed at the beginning of 2022 to 8% at the end of the year. The 2022 Omicron variants (or the context of their occurrence in vaccinated individuals) have in fact been associated, in several studies, with a lower risk of post-COVID-19 condition than earlier variants. This explains why the prevalence of long COVID in the general population has remained stable (4%), while the proportion of the French population infected with SARS-CoV-2 rose from 13% to 48% from the beginning to the end of 2022 (infections dating back at least three months).

Our analyses enabled us to identify a wide range of risk factors for long COVID, including demographic, social, occupational, pathological (comorbidities), behavioral, and perceptual factors, all linked to SARS-CoV-2 infection. The multitude of factors suggests that this condition should not only be considered a direct complication of SARS-CoV-2 infection, but understood and framed within a broad network of contextual, medical, psychological, professional, and social factors that increase an individual’s risk of long COVID, beyond the infection itself. In addition to vaccination and certain behaviors that protect against SARS-CoV-2 infection, these contextual factors should be given greater weight in strategies aimed at reducing the burden of long COVID in the population. Analyses are still underway to clarify the impact of the condition on quality of life and identify population groups—whether clinical (identifiable by specific symptoms) or sociodemographic—at risk of severe deterioration in quality of life.

Despite the stabilization of prevalence in France in 2022, the question of epidemiological monitoring for long COVID still arises, particularly for post-COVID-19 conditions, although monitoring has become difficult given the sharp decline in the use of tests to detect SARS-CoV-2 infection. The latest prevalence estimates obtained in the United States, where monthly monitoring of long COVID continues, show that the phenomenon was not in decline at the start of 2024. The issue of epidemiological monitoring or surveillance is particularly relevant for prolonged cases (31% of cases) and for those whose symptoms have a high or very high impact on daily activities (30%), and likely on healthcare and social protection systems.