Self-Reported Long COVID and Its Association with the Presence of SARS-CoV-2 Antibodies in a Danish Cohort up to 12 Months after Infection

The majority of long coronavirus disease (COVID) symptoms are not specific to COVID-19 and could be explained by other conditions. The present study aimed to explore whether Danish individuals with a perception that they suffer from long COVID have antibodies against the nucleocapsid antigen, as a proxy for detecting previous infection. The study was conducted in February and March 2021, right after the second surge of the COVID-19 pandemic in Denmark. All members of the social media group on Facebook "Covidramte med senfølger" ("long COVID sufferers'') above the age of 17 years and living in Denmark were invited to participate in a short electronic questionnaire about long COVID risk factors and symptoms. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (N) protein was detected in blood samples as a proxy for natural SARS-CoV-2 infection. The final study population comprised 341 participants (90.6% females) who completed blood sampling and answered the questionnaire. A total of 232 (68%) were seropositive (median age, 49.5 years; interquartile range [IQR], 41 to 55 years; 90.1% females). There was no significant difference between sexes and serostatus. Seronegative and seropositive individuals had a similar burden of symptoms that could be attributed to long COVID. Time since perceived COVID-19 was significantly longer in the group of seronegative individuals than the seropositive ones (P < 0.001). This study suggests that long-COVID sufferers are mostly women and showed that a third of the participants did not have detectable anti-N-protein antibodies. It emphasizes the importance of early confirmation of COVID-19, as this study indicates an overlap between long-COVID symptoms and symptoms that are possibly of another origin. IMPORTANCE This cohort study included questionnaire data as well as anti-nucleocapsid antibody analysis, allowing us to determine whether participants were seropositive due to vaccination or natural infection. The study emphasizes the importance of early confirmation of COVID-19, as antibodies recede with time, and it indicates an overlap between long COVID symptoms and symptoms possibly of another origin.

[Post-COVID syndrome: A reflection and opinion paper]

A high proportion of people who have suffered from COVID-19 report, after recovery from the acute phase of the disease, clinical manifestations, both subjective and objective, that continue beyond 3 weeks or even 3 months after the original clinical disease. There is still no agreed nomenclature to refer to this condition, but perhaps the most commonly used is post-COVID syndrome. The Scientific Committee on COVID of the Madrid College of Physicians (ICOMEM) has discussed this problem with a multidisciplinary approach in which internists, infectious disease specialists, psychiatrists, pneumologists, surgeons, geriatricians, pediatricians, microbiologists, family physicians and other specialists have participated, trying to gather the existing information and discussing it in the group. The clinical manifestations are very variable and range from simple fatigue to persistent fibrosing lung lesions with objective alterations of pulmonary function. Post-COVID syndrome seems to be particularly frequent and severe in adults who have required admission to Intensive Care Units and has a peculiar behavior in a very small group of children. The post-COVID syndrome, which undoubtedly exists, is at first sight not clearly distinguishable from clinical manifestations that which occur after other acute viral diseases and after prolonged stays in ICUs due to other diseases. Therefore, it offers excellent research opportunities to clarify its pathogenesis and possibly that of other related entities. It is possible that progressively there will be an increased demand for care among the millions of people who have suffered and overcome acute COVID for which the health authorities should design mechanisms for the agile management of care that will possibly require well-coordinated multidisciplinary groups. This paper, structured in questions on different aspects of the post-COVID syndrome, attempts to stage the current state of this problem.