Those distributions were reordered to have non-decreasing functions. Let P j and P k, j ( M e d k ) be the people of age j in the Italian and in fictitious populations, respectively, on the kth pandemic day, using the definition of “median” we have thatĭates of the ISS cumulative distribution of detected cases by age correlate with the most recent update. For the precedent period (during which the ISS only released the median age of detected cases), we constructed fictitious populations P ( M e d k ) with median ages ( MEDs) equal to those estimated and with the age structure related with that of Italian population provided by the ISTAT 7. ), was used the daily age distribution of detected cases released by the ISS from Decem( f k, j ( I S S )) 3. ) daily estimates from 5 were used.ħ) As estimates of age distribution of total infections ( N k, j. The more a VOC is prevalent, the lesser the introduced bias.Ħ) As daily fraction of infections for each VOC (ξ = 0, 1, …, 5) by age class ( N k, j, ξ. ), the daily fraction of vaccinated population by age class 4 were used. Let X k ( j ) be the binary random variable representing the outcome (1 = dead 0 = recovered) of the jth person infected on the kth day of the pandemicĥ) As estimates of the fraction of vaccinated infections by age class and VOC ( N k, j, ξ, V N k, j, ξ. Modeling the incidence of infections (negative binomial distribution) Once the main formulas are established, the estimated variables used to determine the solutions will be given in the Section Estimating the Daily Lethality. In the following, we will proceed with the mathematical formulation, which will be progressively upgraded, in the next sections, to consider the more complex probabilities involving age classes, different strains, and vaccination level. While relatively low in the whole population (υ k) of estimates (Sections Estimating D k and υ k: Weighted Moving Average and Checking Estimates). The lethality of the original strain was estimated using infection fatality ratios (IFR) assessed through several national sero-surveys ( 6, 7). Unlike other coronaviruses, the SARS-CoV-2 is able to spread through pre- and asymptomatic infections that are difficult to detect and isolate, requiring health authorities to test all contacts of confirmed cases to lower the risk of spread ( 4, 5). The virus spread so quickly around the world that the World Health Organization (WHO) declared the COVID-19 a Public Health Emergency of International Concern on Januand a pandemic on March 11, 2020, ( 3). SARS-CoV-2 causes the coronavirus disease 2019 (COVID-19), an illness that ranges from mild flu symptoms to bilateral interstitial pneumonia ( 2). The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a new virus identified in Wuhan (Hubei, China) in late 2019 ( 1). Despite the variants of concern, vaccines strongly reduced the pandemic impact on the healthcare system avoiding strong restriction measures.

Mobility restriction measures were an effective suppression strategy while distance learning and smart working were effective mitigation strategies.

From the second year, a massive test campaign made it possible to detect more asymptomatic cases, especially among the youngest. During the 2nd year of the pandemic, vaccines prevented 10,000,000 infections and 115,000 deaths.Ĭonclusion: Almost 40% of COVID-19 infections have gone undetected and they were mostly concentrated in the first year of the pandemic. Restriction measures of population mobility strongly slowed the viral spread. The first two waves had the highest number of daily deaths (about 710) and the last wave showed the highest peak of daily infections (220,487). The overall lethality rate was 0.73%, but daily it ranged from 2.78% (in the first wave) to 0.15% (in the last wave). The lethality of the original strain (estimated through national sero-surveys) was adjusted daily for age of infections, hazard ratios of virus variants, and the cumulative distribution of vaccinated individuals. This paper aims to provide a detailed overview of the first 2 years of the pandemic in Italy.ĭesign and methods: Using the negative binomial distribution, the daily incidence of infections was estimated through the virus's lethality and the moving-averaged deaths. Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, Italian National Workers' Compensation Authority (INAIL), Rome, Italyīackground: The novel coronavirus disease 2019 (COVID-19) is an ongoing pandemic that was first recognized in China in December 2019.

Italy lockdown timeline