VIROLOGICAL AND IMMUNOLOGICAL FEATURES OF SARS-COV-2 INFECTED CHILDREN WITH DISTINCT SYMPTOMATOLOGY (preprint)

BACKGROUND: Despite SARS-CoV-2 immunizations have started in most countries, children are not currently included in the vaccination programs, thus it remains crucial to define their anti-SARS-CoV-2 immune response in order to minimize the risk for other epidemic waves. This study seeks to provide a description of the virology ad anti-SARS-CoV-2 immunity in children with distinct symptomatology. METHODS: Between March and July 2020, we recruited 15 SARS-CoV-2 asymptomatic (AS) and 51 symptomatic children (SY), stratified according to WHO clinical classification. We measured SARS-CoV-2 viral load using ddPCR and qPCR in longitudinally collected nasopharyngeal swabs samples. To define anti-SARS-CoV-2 antibodies we measured neutralization activity and total IgG load (Diasorin). We also evaluated antigen-specific B and CD8+T-cells, using a labelled S1+S2 protein and ICAM expression, respectively. Plasma protein profiling was performed with Olink. RESULTS: Virological profiling showed that AS had lower viral load at diagnosis (p=0.004) and faster virus clearance (p=0.0002) compared to SY. Anti-SARS CoV-2 humoral and cellular response did not appear to be associated with the presence of symptoms. AS and SY showed similar titers of SARS-CoV-2 IgG, levels of neutralizing activity, and frequency of Ag-specific B and CD8+T-cells. Whereas pro-inflammatory plasma protein profile was associated to symptomatology. CONCLUSION: We demonstrated the development of anti-SARS-CoV-2 humoral and cellular response with any regards to symptomatology, suggesting the ability of both SY and AS to contribute towards herd immunity. The virological profiling of AS suggested that they have lower virus load associated with faster virus clearance.

The differential impact of physical distancing strategies on social contacts relevant for the spread of COVID-19 (preprint)

Physical distancing measures are intended to mitigate the spread of COVID-19. However, the impact these measures have on social contact and disease transmission patterns remains unclear. We ran the first comparative contact survey (N=53,708) across eight countries (Belgium, France, Germany, Italy, Netherlands, Spain, United Kingdom, United States) for the period March 13 - April 13, 2020. Our results show that social contact numbers mainly decreased after governments issued physical distancing guidelines rather than after announcing national lockdown measures. Compared to pre-COVID levels, social contact numbers decreased by 48% - 85% across countries. Except in Italy, these reductions were smaller than those observed in Wuhan (China). However, they sufficed to bring the R0 below one in almost every context considered. Finally, in all countries studied, the numbers of contacts decreased more rapidly among older people than among younger people, indicating higher levels of protection for groups at greater risk.

Behaviors and attitudes in response to the COVID-19 pandemic: Insights from a cross-national Facebook survey (preprint)

In the absence of medical treatment and vaccination, the mitigation and containment of the ongoing COVID-19 pandemic relies on behavioral changes. Timely data on attitudes and behaviors are thus necessary to develop optimal intervention strategies and to assess the consequences of the pandemic for different demographic groups. We developed a rapid response monitoring system via a continuously run online survey (the "COVID-19 Health Behavior Survey") across eight countries (Belgium, France, Germany, Italy, the Netherlands, Spain, the United Kingdom, the United States). The survey was specifically designed to collect key information on people's health status, behaviors, close social contacts, and attitudes in response to the COVID-19 pandemic. We developed an innovative approach to recruit participants via targeted Facebook advertisement campaigns in order to generate balanced samples for post-stratification. In this paper, we present results for the period from March 13-April 19, 2020. We estimate important differences by sex: women show a substantially higher perception of threat along with a lower level of confidence in the health system. This is paralleled by sex-specific behaviors, with women more likely to adopt a wide range of preventive behaviors. We thus expect behavior to serve as a protective factor for women. Our findings also show a higher level of awareness and concern among older respondents, in line with the evidence that the elderly are at highest risk of severe complications following infection from COVID-19. While across all the samples respondents were less concerned for themselves than for their country or for the world, we also observed substantial temporal and spatial heterogeneity in terms of confidence in institutions and responses to non-pharmaceutical interventions.