Balazs Madas, Centre for Energy Research, Budapest, Budapest, Hungary. Title: Deposition distribution of the new coronavirus (SARS-CoV-2) in the human airways upon exposure to cough-generated droplets and aerosol particles. Abstract: While huge efforts have been made to understand the spread of COVID-19 as well as the pathogenesis following cellular entry, much less attention is paid to how SARS-CoV-2 from the environment reach the receptors of the target cells. The aim of this study is to characterize the deposition distribution of SARS-CoV-2 in the airways upon exposure to cough-generated droplets and aerosol particles. For this purpose, the Stochastic Lung Deposition Model has been applied. Particle size distribution, breathing parameters supposing normal breathing through the nose, and viral loads were taken from the literature. We found that the probability of direct infection of the acinar airways due to inhalation of particles emitted by a bystander cough is very low. As the number of viruses deposited in the extrathoracic airways is about 7 times higher than in the acinar airways, we concluded that in most cases COVID-19 pneumonia must be preceded by SARS-CoV-2 infection of the upper airways. Our results suggest that without the enhancement of viral load in the upper airways, COVID-19 would be much less dangerous. The period between the onset of initial symptoms and the potential clinical deterioration could provide an opportunity for prevention of pneumonia by blocking or significantly reducing the transport of viruses towards the acinar airways. Therefore, even non-specific treatment forms like disinfection of the throat and nasal and oral mucosa may effectively keep the viral load of the upper airways low enough to avoid or prolong the progression of the disease. In addition, using a tissue or cloth in order to absorb droplets and aerosol particles emitted by own coughs of infected patients before re-inhalation is highly recommended even if they are alone in quarantine. YouTube and Slides.

Yinon Moise Bar-On, Weizmann Institute of Science. Title: Booster protection against COVID19 confirmed infections and severe disease. Abstract:  The early initiation of a nationwide vaccination campaign in Israel, led to a sharp decrease in the incidence of COVID-19 between mid-January 2021 and June 2021. Nevertheless, the emergence of the delta variant, and waning immunity has led to a recent resurgence in both confirmed infection and severe illness. 

In an effort to curb this resurgence, Israeli authorities approved the administration of a booster dose, first to the 60+ population and later to the entire 16+ population who received a second dose >5 months earlier. 

We analyze a nationwide database including data on about 5 million individuals to estimate the effect of the administration of the booster dose on the rates of confirmed infection and severe illness. YouTube and Slides.