The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified for the first time in the late 2019 in the city of Wuhan (Hubei, China). [1] It causes the coronavirus disease 2019 (COVID-19) with symptoms ranging from mild flu-like symptoms to severe pneumonia [2]. The World Health Organization (WHO) declared the outbreak a Public Health Emergency of International Concern from 30 January, 2020 to May 5, 2023 and a pandemic on 11 March 2020 [3]. The virus quickly spread all around the world, and during the first two years of the pandemic (January 2020 ro December 2021), the weekly updated WHO data reported 280,614,414 confirmed cases and 5,446,891 deaths1. One of the most significant social effects of the pandemic was its profound impact on hospital capacities worldwide [4]. In 2020-2021, the European Centre for Disease Prevention and Control (ECDC) reported 12,563,619 of Covid-19 hospitalizations in Austria, Belgium, Bulgaria, Cyprus, Czechia, Estonia, France, Ireland, Liechtenstein, Lithuania, Luxemburg, Netherland, Romania, Slovakia, Slovenia, Spain2. In the same period in US, the Centers for Disease Control and Prevention reported 3,719,818 hospitalizations in the whole country3. During the peaks of transmission, health systems in many countries were overwhelmed, and due to the complexity of treating COVID-19 patients, especially in intensive care units, hospitalization costs increased worldwide. A systematic review found that in Germany the total cost of hospitalization in intensive care per patient was 100,789 USD (5). Even if the world was not prepared nor coordinated to such emergency, there was an impressive mobilization of human societies worldwide. Virus lethality of the original strain was quickly estimated by the infection fatality ratio (IFR) assessed through several national serosurveys [6,7]. By the end of 2020, global Medicines Agencies had conditionally approved several vaccines based on different technologies, with others close behind (8,9). Most governments established unprecedented public health policies, such as social distancing, remote working, and lockdowns, to reduce the spread of the virus (10,11). Furthermore, there was an impressive proliferation of mathematical models aimed to predict and manage the pandemic as well as evaluate the implemented policies (12). Italy was the first European country to be hit by the new virus and declared a health emergency status from January 31, 2020 to the 31 of march 2022. The unexpected high speed of transmissions quickly caused hospitals saturation and forced the governmental administration to establish a national lockdown. The hardest period was during the first two years of pandemic, before the vaccination campaign (started in last days of 2020) began to have the desired effects. To increase the health system resilience, it is important to study hospitalizations and the related financial burdens due to COVID-19. This article is part of a broader project focused on assessing hospital characteristics associated with principal occupational respiratory diseases, including COVID-19, which is recognized as an occupational injury under specific conditions when contracted in the workplace. It aims to describe the COVID-19 hospitalizations in Italy and estimate the associated costs with these cases.

The recent COVID-19 pandemic has highlighted global unpreparedness for managing the consequences of the emergence of a new virus with a high transmission rate. During the peaks of infection waves, many national health systems were pushed to the brink of collapse, and extreme measures to reduce contagion, such as lockdowns, proved to be the only effective countermeasures. These measures significantly impacted economic growth and public health worldwide (15,16). By describing significant hospital characteristics and estimating hospitalization costs, this paper can support effective analyses aimed at improving the resilience of health systems for future challenges. Hospitalization costs for COVID-19 patients have been estimated worldwide, but comparisons among countries are impractical because studies have utilized different methods for calculating the costs. This variability has negatively impacted the comparability of costs across studies (5,17). However, knowing the costs of hospitalizations in a country allows us to better prepare for the future from various points of view, ranging from hospital resilience to compensation for infections of healthcare workers and for workers with a high contact rate with the public. By starting from patients’ characteristics, we can note that the sinusoidal-like pattern observed in the admission rates across age groups may be attributed to several factors. For example, infants typically have closer contact with their parents than children aged 1-4 years do, potentially making them more susceptible to household transmission. Additionally, this pattern could partly result from heightened protective measures implemented for infants as compared to children aged 1-14 years. In both cases, conducting widespread testing campaigns and rigorous contact tracing efforts significantly contributes to monitor the virus epidemiology and slowing virus transmission. It is also important to highlight that the high percentage of patient transfers could be attributed to the initial hospitals being overwhelmed and that the death rate among the oldest individuals was very high, ranging from 30 to 40%. Without efficient primary care, emergency rooms in hospitals have often become the front line against the virus, thereby overexposing health workers to the risk of infection. Simultaneously, vulnerable individuals have probably not received sufficient protection or treatment during the initial phase of the infection. Finally, the COVID-19 represented the 5.6% of the total admissions, 11% of total length of stay and 17% of the total cost in the considered period. The admission in intensive care more than doubled the cost per hospitalization in both years to almost 23.000-24.000 euros while it increased the daily cost of 1.8 times in 2020 (from 770 to 1355 euros) and of 1.5 times in 2021 (from 815 to 1229 euros). Those figures resume the highest impact the pandemic had on the health system. Especially in the first months of pandemic, hospitals in areas where the virus was spreading faced a tsunami of emerging infections and healthcare and social workers paid a very high cost with a percentage of complaints at work equal to 62% of the total5. Implementing a protective pad around the entire health system that leverages networks of family doctors and nurses, connected in real time to the entire health system, can be crucial. Such a network, tasked with supporting the monitoring of the local epidemiological situation, protecting vulnerable individuals also through telehealth visits, and establishing a triage system for infections in the initial phase, can effectively help manage virus spread and protect hospitals from unpredictable waves of admission demand. To strengthen the primary health care could make the difference for the future and could increase the system resilience facing new challenges.

This paper has two main limitations. Firstly, we categorized hospitalizations with the ICD-9-CM treatment code of 93.9 as admissions to intensive care, which represent approximately 5% of total hospitalizations instead of the expected 10% (18). Secondly, we did not account for the costs associated with waiting for hospital beds for acute COVID-19 patients nor the costs related to waiting in emergency departments for the management of confirmed and suspected COVID-19 cases.