Vulnerability to SARS-CoV-2 infection and disease: ripping the curl after the storm.

SARS-CoV-2 infection now seems to have entered the announced endemic phase. The population's immunity is increasingly more robust, thanks to successive vaccination and booster campaigns, and the almost inevitable exposure and re-exposure to the virus itself, which has truly served as a natural immunizing mechanism. On the other hand, the genetic drift of the virus is leading it to become another catarrhal agent, as are the other endemic human coronaviruses. However, it should not be lost sight of that there are still segments of the population with susceptibility to severe COVID, who will be candidates to continue receiving vaccine boosters or antiviral drugs in the initial stages of infection.

POSB174 Clinical and Economic Impact of Non-Pharmacological Interventions on the COVID-19 Pandemic: A Predictive Model Based on the Spanish Case

Objectives: With over 172 million cases and 3.7 million deaths worldwide, the COVID-19 pandemic has overwhelmed health systems forcing governments to implement non-pharmacological interventions (NPI) to control the spread of the disease. Spain was one of the first and most severely impacted countries by the COVID-19 pandemic. The models developed herein aim to assess the clinical and economic consequences of such NPI, based on the Spanish case. Methods: Two separate models were developed to assess the epidemiological and economic impacts of different NPI (i.e. social restrictions and testing) on the COVID-19 pandemic. First, a dynamic, modified, Susceptible-Exposed-Infectious-Removed (SEIR) model was developed. Then, the output from the SEIR model was used in the second model to estimate direct healthcare costs and Gross Domestic Product (GDP) changes using a regression model which correlated different NPI and GDP changes observed across 42 countries. Overall, 13 scenarios combining different NPIs based on social restrictions and testing rates were simulated through both models. Results: Based on the results from the SEIR simulation both increased social restrictions (Composite COVID-19 Stringency Index≥73) and increased testing rates (positivity≤1%) would manage to control the COVID-19 spread. However, notable differences are observed in terms of direct healthcare costs and GDP impact. Policies entailing increased testing rates translated into higher healthcare costs and lower GDP decline (vs. same quarter from previous year), whereas increased social restrictions are correlated with greater GDP declines, with differences of up to 4.4% points among scenarios. Increased test sensitivity also leads to higher reductions on cases, hospitalizations and deaths. Conclusions: Increased testing appears to be able to control the COVID-19 pandemic while minimizing the GDP impact. These models may provide evidence for decision makers during future pandemics and in countries where vaccination rates are still low helping to better balance health and socioeconomic concerns.

Approach to COVID-19 pandemic management in Madrid. Chronic of a year.

After more than a year of pandemic, the international medical community has changed the perception of fear to one of respect for SARS-COV-2. This has been the consequence of the integral study of all the dimensions of the disease, from viral recombinant capacity to transmissibility, diagnosis, care and prevention. This document summarizes the main strategic lines of study and approach to the pandemic in Madrid.

Infection and infectivity: Utility of rapid antigen tests for the diagnosis of COVID-19.

Detection of SARS-CoV-2 proteins is commercially available in the form of lateral-flow rapid antigen test for the point-of-care diagnosis of COVID-19. This platform has been validated for symptomatic and asymptomatic individuals, for diagnosis or screening, and as part of single or sequential diagnostic strategies. Although in general less sensitive than amplification techniques, antigen tests may be particularly valid during the first days of symptoms and to detect individuals with greater viral load, thereby with enhanced chances of viral transmission. The simplicity of antigen tests make them very suitable to discard infection in settings with low pretest probability, and to detect infection in case of higher chances of having COVID-19.

Temporary hospitals in times of the COVID pandemic. An example and a practical view.

We describe the most widely used temporary hospital in Europe during the first pandemic wave, its structure, function, and achievements. Other models of care developed during the pandemic around the world were reviewed including their capacity, total bed/ICU bed ratio and time of use. We particularly analyzed the common and differential characteristics of this type of facilities. IFEMA Exhibition Center was transformed into a temporary 1,300-bed hospital, which was in continuous operation for 42 days. A total of 3,817 people were treated, generally patients with mild to moderate COVID-19, 91% of whom had pneumonia. The average length of stay was 5 to 36 days. The most frequent comorbidities were hypertension (16.5%), diabetes mellitus (9.1%), COPD (6%), asthma (4.6%), obesity (2.9%) and dementia (1.6%). A total of 113 patients (3%) were transferred to another centers for aggravation, 19 (0.5%) were admitted to ICU and 16 patients (0.4%) died. An element of great help to reducing the overload of care in large hospitals during peaks of health emergencies could be these flexible structures capable of absorbing the excess of patients. These must be safe, breaking domestic transmission and guarantee social and emotional needs of patients. The success of these structures depends on delimitation in admission criteria taking into account the proportion of patients who may require, during admission, assistance in the critical care area.

Recommendations for use of antigenic tests in the diagnosis of acute SARS-CoV-2 infection in the second pandemic wave: attitude in different clinical settings.

The high transmissibility of SARS-CoV-2 before and shortly after the onset of symptoms suggests that only diagnosing and isolating symptomatic patients may not be sufficient to interrupt the spread of infection; therefore, public health measures such as personal distancing are also necessary. Additionally, it will be important to detect the newly infected individuals who remain asymptomatic, which may account for 50% or more of the cases. Molecular techniques are the "gold standard" for the diagnosis of SARS-CoV-2 infection. However, the massive use of these techniques has generated some problems. On the one hand, the scarcity of resources (analyzers, fungibles and reagents), and on the other the delay in the notification of results. These two facts translate into a lag in the application of isolation measures among cases and contacts, which favors the spread of the infection. Antigen detection tests are also direct diagnostic methods, with the advantage of obtaining the result in a few minutes and at the very "pointof-care". Furthermore, the simplicity and low cost of these tests allow them to be repeated on successive days in certain clinical settings. The sensitivity of antigen tests is generally lower than that of nucleic acid tests, although their specificity is comparable. Antigenic tests have been shown to be more valid in the days around the onset of symptoms, when the viral load in the nasopharynx is higher. Having a rapid and real-time viral detection assay such as the antigen test has been shown to be more useful to control the spread of the infection than more sensitive tests, but with greater cost and response time, such as in case of molecular tests. The main health institutions such as the WHO, the CDC and the Ministry of Health of the Government of Spain propose the use of antigenic tests in a wide variety of strategies to respond to the pandemic. This document aims to support physicians involved in the care of patients with suspected SC2 infection, in the context of a growing incidence in Spain since September 2020, which already represents the second pandemic wave of COVID-19.