Incidence, symptom clusters and determinants of post-acute COVID symptoms: a population-based surveillance in community-dwelling users of the COVID RADAR app.

OBJECTIVES: This study aims to describe the incidence, symptom clusters and determinants of post-acute COVID symptoms using data from the COVID RADAR app in the Netherlands. DESIGN: Prospective cohort. SETTING: General population in the Netherlands from April 2020 to February 2022. PARTICIPANTS: A total of 1478 COVID RADAR app users, with data spanning 40 days before to 100 days after positive SARS-CoV-2 test. OUTCOME MEASURES: Incidence and duration of 10 new symptoms that developed during acute infection, defined as 10 days prior and 10 days after positive test. Clustering of these post-acute COVID symptoms and associations between factors known in the acute phase and 100-day symptom persistence. RESULTS: The most frequent post-acute symptoms were cough, loss of smell or taste and fatigue. At 100 days postinfection, 86 (8%) participants still experienced symptoms. Three post-acute COVID symptom clusters were identified: non-respiratory (headache and fatigue; 49% of participants with post-acute COVID symptoms); olfactory (15%) and respiratory (8%). Vaccination was associated with a lower risk of post-acute COVID symptoms 100 days after infection, although CIs were wide (OR: 0.5; 95% CI: 0.2 to 1.5), but not with non-respiratory symptoms (OR: 1.0; 95% CI: 0.3 to 4.4). Severe acute disease increased the risk of post-acute COVID symptoms (OR: 1.4; 95% CI: 1.2 to 1.5; per additional acute symptom). CONCLUSIONS: In this cohort of infected community-dwelling app users, 5%-10% experienced post-acute COVID symptoms. The symptoms cluster in several distinct entities, which differ in incidence, patient characteristics and vaccination effects. This suggests multiple mechanisms underlying the development of post-acute COVID symptoms.

Coagulation and inflammatory response after intramuscular or intradermal mRNA-1273 SARS-CoV-2 vaccine: secondary analysis of a randomized trial.

Background: Fractional-dosed intradermal (i.d.) vaccination produces antibody concentrations above the proposed proxy for protection against severe disease as compared with intramuscular (i.m.) vaccination and may be associated with a decreased prothrombotic effect. Objectives: To assess changes in coagulation following standard dosed i.m. or fractional-dosed i.d. (one-fifth of i.m.) mRNA-1273 SARS-CoV-2 vaccine and to determine the association between the inflammatory response and coagulation. Methods: This study was embedded in a randomized controlled trial assessing the immunogenicity of an i.d. fractional-dosed mRNA-1273 vaccine. Healthy participants, aged 18 to 30 years, were randomized (2:1) to receive either 2 doses of i.d. or i.m. vaccine. Blood was drawn prior to first and second vaccination doses and 1 and 2 weeks after the second dose. The outcomes were changes in coagulation parameters (primary endpoint peak height of the thrombin generation curve) and inflammation (high-sensitivity C-reactive protein [hs-CRP]). Results: One hundred twenty-three participants were included (81 i.d.; 42 i.m.). Peak height increased after vaccination (i.m., 28.8 nmol; 95% CI, 6.3-63.8; i.d., 17.3 nmol; 95% CI, 12.5-47.2) and recovered back to baseline within 2 weeks. I.m. vaccination showed a higher inflammatory response compared with i.d. vaccination (extra increase hs-CRP, 0.92 mg/L; 95% CI, 0.2-1.7). Change in endogenous thrombin potential was associated with change in hs-CRP (beta, 28.0; 95% CI, 7.6-48.3). Conclusion: A transient increase in coagulability after mRNA-1273 SARS-CoV-2 vaccination occurred, which was associated with the inflammatory response. While i.d. administration showed antibody concentrations above the proposed proxy for protection against severe disease, it was associated with less systemic inflammation. Hence, i.d. vaccination may be safer.

[Indoor sporting during the COVID-19 pandemic: analysis with data from the COVID RADAR app]. / Binnensporten tijdens de COVID-19-pandemie: analyse met behulp van data uit de COVID RADAR app.

Indoor sporting locations have been forced to stay closed longer than outdoor sporting locations during the lockdowns introduced during the COVID-19 pandemic. This research addresses the question whether exercising indoors does raise one's risk of infection with SARS-CoV­2. This analysis was performed using data from the COVID RADAR app and accounted for user differences in age, vaccine status, sex, other risky behavior, SARS-CoV­2 prevalence and quality of living environment. Analyzing data from 1,353 users, 13.1% of which reported a positive SARS-CoV­2 test, we found that exercising indoors leads to an odds ratio of 1.8 with a positive SARS-CoV­2 test (95%-confidence interval 1.2-2.6, p = 0.003), as compared to users who exercise outdoors. This confirms the justification used in longer closing indoor sporting locations to reduce the number of infections.

COVID RADAR app: Description and validation of population surveillance of symptoms and behavior in relation to COVID-19.

BACKGROUND: Monitoring of symptoms and behavior may enable prediction of emerging COVID-19 hotspots. The COVID Radar smartphone app, active in the Netherlands, allows users to self-report symptoms, social distancing behaviors, and COVID-19 status daily. The objective of this study is to describe the validation of the COVID Radar. METHODS: COVID Radar users are asked to complete a daily questionnaire consisting of 20 questions assessing their symptoms, social distancing behavior, and COVID-19 status. We describe the internal and external validation of symptoms, behavior, and both user-reported COVID-19 status and state-reported COVID-19 case numbers. RESULTS: Since April 2nd, 2020, over 6 million observations from over 250,000 users have been collected using the COVID Radar app. Almost 2,000 users reported having tested positive for SARS-CoV-2. Amongst users testing positive for SARS-CoV-2, the proportion of observations reporting symptoms was higher than that of the cohort as a whole in the week prior to a positive SARS-CoV-2 test. Likewise, users who tested positive for SARS-CoV-2 showed above average risk social-distancing behavior. Per-capita user-reported SARS-CoV-2 positive tests closely matched government-reported per-capita case counts in provinces with high user engagement. DISCUSSION: The COVID Radar app allows voluntarily self-reporting of COVID-19 related symptoms and social distancing behaviors. Symptoms and risk behavior increase prior to a positive SARS-CoV-2 test, and user-reported case counts match closely with nationally-reported case counts in regions with high user engagement. These results suggest the COVID Radar may be a valid instrument for future surveillance and potential predictive analytics to identify emerging hotspots.