ABSTRACT
We aimed to assess differences in the summer excess of mortality by COVID-19 history using data from the mortality and COVID-19 surveillances. We found 4% excess risk in 2022 summer, compared to 2015-2019. A mortality rate ratio of 1.59 (95%CI 1.39-1.82) for COVID-19 survivors compared to naive, was found. Both were higher in people aged [≥]75 years. During the July heat wave, the excess for COVID-19 survivors decreased and disappeared when excluding people living in nursing homes. Funding statementThis study was partially supported by the Italian Ministry of Health -CCM 2020 - "Sorveglianza epidemiologica e controllo del COVID-19 in aree urbane metropolitane e per il contenimento della circolazione del Sars-CoV-2 nella popolazione immigrata in Italia" and by the Ricerca Corrente 2023 HighlightsO_LIthe excess of mortality in COVID-19 survivors is not exacerbated by heatwaves C_LIO_LIan excess of mortality during the whole summer in COVID-19 survivors aged over 75 suggest that no harvesting effect is appreciable in the older population that survived COVID-19 C_LIO_LIFor COVID-19 survivors aged over 75, a lower mortality than the naive population was observed only during the July heat wave when we stratified by residency C_LI
ABSTRACT
Undernotification of SARS-CoV-2 infections has been a major obstacle to the tracking of critical quantities such as infection attack rates and the probability of severe and lethal outcomes. We use a model of SARS-CoV-2 transmission and vaccination informed by epidemiological and genomic surveillance data to estimate the number of daily infections occurred in Italy in the first two years of pandemic. We estimate that the attack rate of ancestral lineages, Alpha, and Delta were in a similar range (10-17%, range of 95% CI: 7-23%), while that of Omicron until February 20, 2022, was remarkably higher (51%, 95%CI: 33-70%). The combined effect of vaccination, immunity from natural infection, change in variant features, and improved patient management massively reduced the probabilities of hospitalization, admission to intensive care, and death given infection, with 20 to 40-fold reductions during the period of dominance of Omicron compared to the initial acute phase.
ABSTRACT
The SARS-CoV-2 variant of concern Omicron was first detected in Italy in November 2021. Data from three genomic surveys conducted in Italy between December 2021 and January 2022 suggest that Omicron became dominant in less than one month (prevalence on January 3: 78.6%-83.8%) with a doubling time of 2.7-3.1 days. The mean net reproduction number rose from about 1.15 in absence of Omicron to a peak of 1.83 for symptomatic cases and 1.33 for hospitalized cases, while it remained stable for critical cases.
ABSTRACT
BackgroundWe aimed to quantify the risk of transmission of SARS-CoV-2 in the school setting by type of school, characteristics of the index case and calendar period in the Reggio Emilia province (RE), Italy. The secondary aim was to estimate the promptness of contact tracing. MethodsA population-based analysis of surveillance data of all COVID-19 cases occurring in RE, Italy, from September 1, 2020, to April 4th, 2021, for which a school contact and/or exposure was suspected. Indicator of the delay in contact tracing was computed as the time elapsed since positivity of the index case and the date on which the swab for classmates was scheduled (or most were scheduled). ResultsOverall, 30,184 and 13,608 contacts among classmates and teachers/staff, respectively, were identified and received recommendation for testing; 43,214 (98.7%) performed the test. Secondary transmission occurred in about 40% of the investigated classes, and the overall secondary case attack rate was 4%, slightly higher when the index case was a teacher, but with almost no differences by type of school and stable during the study period. Promptness of contact tracing increased during the study period, reducing the time from index case identification and testing of contacts from 7 to 3 days, as well the ability to identify possible source of infection in the index case. ConclusionsDespite the spread of the Alpha variant during the study period in RE, the secondary case attack rate remained stable from school reopening in September 2020 until the beginning of April 2021.
ABSTRACT
SARS-CoV-2 variants of concern (B.1.1.7, P.1 and B.1.351) have emerged in different continents of the world. To date, little information is available on their ecological interactions. Based on two genomic surveillance surveys conducted on February 18 and March 18, 2021 across the whole Italian territory and covering over 3,000 clinical samples, we found significant co-circulation of B.1.1.7 and P.1. We showed that B.1.1.7 was already dominant on February 18 in a majority of regions/autonomous provinces (national prevalence 54%) and almost completely replaced historical lineages by March 18 (dominant in all regions/autonomous provinces, national prevalence 86%). At the same time, we found a substantial proportion of cases of the P.1 lineage on February 18, almost exclusively in Central Italy (with an overall prevalence in the macro-area of 18%), which remained at similar values on March 18, suggesting the inability by this lineage to outcompete B.1.1.7. Only 9 cases from variant B.1.351 were identified in the two surveys. At the national level, we estimated a mean relative transmissibility of B.1.1.7 (compared to historical lineages) ranging between 1.55 and 1.57 (with confidence intervals between 1.45 and 1.66). The relative transmissibility of P.1 estimated at the national level varied according to the assumed degree of cross-protection granted by infection with other lineages and ranged from 1.12 (95%CI 1.03-1.23) in the case of complete immune evasion by P.1 to 1.39 (95%CI 1.26-1.56) in the case of complete cross-protection. These observations may have important consequences on the assessment of future pandemic scenarios.
ABSTRACT
Vaccination campaigns against COVID-19 are allowing the progressive release of physical distancing restrictions in many countries. However, the global spread of the highly transmissible Delta variant has likely suppressed the residual chances of SARS-CoV-2 elimination through herd immunity alone. Here we assess the impact of the vaccination program in Italy since its start on December 27, 2020 and evaluate possible prospects for reopening the society while at the same time keeping COVID-19 under control. To this aim, we propose a mathematical modeling framework where levels of social activity are adjusted to match the time-series of the net reproduction number as estimated from surveillance data. We compared the estimated level of social contacts, number of deaths, and transmission potential with those of a counterfactual scenario where the same epidemic trajectory is obtained in absence of vaccination. We then evaluate the prospective impact of different scenarios of vaccination coverage and different social activity levels on SARS-CoV-2 reproduction number. We estimate that by June 30, 2021, the COVID-19 vaccination program allowed the resumption of about half the social contacts that were recorded in pre-pandemic times; in absence of vaccination, only about one third could have been resumed to obtain the same number of cases, with the added cost of about 12,100 (95%CI: 6,600-21,000) extra deaths (+27%; 95%CI: 15-47%) between December 27, 2020 and June 30, 2021. We show that the negative effect of the Delta variant diffusion in July was entirely offset by vaccination in the month of July and August 2021. Finally, we estimate that a complete return to the pre-pandemic life could be safely attained only if >90%, including children from 5 years on, will be vaccinated using mRNA vaccines developed in 2020. In any case, increasing the vaccination coverage will allow further margins for societal reopening even in absence of a pediatric vaccine. These results may support the definition of vaccination targets for countries that have already achieved a broad population coverage.
ABSTRACT
To counter the second COVID-19 wave in autumn 2020, the Italian government introduced a system of physical distancing measures organized in progressively restrictive tiers (coded as yellow, orange, and red) and imposed on a regional basis according to epidemiological risk assessments. The individuals attendance to locations outside the residential settings was progressively reduced with tiers, but less than during the national lockdown against the first COVID-19 wave in the spring. The reproduction number Rt decreased below the epidemic threshold in 85 out of 107 provinces after the introduction of the tier system, reaching average values of about 0.99, 0.89 and 0.77 in the yellow, orange and red tier, respectively. We estimate that the reduced transmissibility resulted in averting about 37% of the hospitalizations between November 5 and November 25, 2020. These results are instrumental to inform public health efforts aimed at preventing future resurgence of cases.
ABSTRACT
BackgroundSchool closures was one of the main measures undertaken to reduce the number of social contacts during the first wave of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. We aimed to describe the data on secondary transmission of SARS-CoV-2 among students and teachers/personnel after the reopening of preschools and schools in Reggio Emilia, Italy. MethodsThis prospective population-based study included all consecutive cases leading to an investigation in 41 classes of 36 educational institutions (8 infant-toddler centres and preschools, 10 primary and 18 secondary schools) in the period September 1 - October 15, 2020, in Reggio Emilia province, Italy. We report the characteristics of the school, of the index case, including the possible source of infection, the number of contacts (students and teachers/personnel) that were identified and tested and the characteristics of secondary cases. ResultsIn the study period, 994 students and 204 teachers were tested during related investigations due to notification of 43 primary cases (38 among students and 5 among teachers). Of these, 10 students and two teachers created 39 secondary cases, resulting in an attack rate of 3.9%. There were no secondary cases among teachers/stuff. Secondary transmission occurred in one primary school and 8 secondary schools. Except for two students and one teacher, the possible source of infection for all index cases was identified as they had all had previous contact with a positive case; the majority of secondary cases did not report any previous close contact with a positive case. The clusters ranged from one to 22 secondary cases. ConclusionsTransmission at school occurred in a non-negligible number of cases, particularly in secondary schools. Prompt testing and isolation of classmates could probably reduce the risk of transmission in school settings.
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BackgroundInternational literature suggests that disadvantaged groups are at higher risk of morbidity and mortality from SARS-CoV-2 infection due to poorer living/working conditions and barriers to healthcare access. Yet, to date, there is no evidence of this disproportionate impact on non-national individuals, including economic migrants, short-term travellers, and refugees. MethodsWe analysed data from the Italian surveillance system of all COVID-19 laboratory-confirmed cases tested positive from the beginning of the outbreak (20th of February) to the 19th of July 2020. We used multilevel negative-binomial regression models to compare the case-fatality rate and the rate of admission to hospital and intensive care unit (ICU) between Italian and non-Italian nationals. The analysis was adjusted for differences in demographic characteristics, pre-existing comorbidities, and period of diagnosis. ResultsWe analysed 213,180 COVID-19 cases, including 15,974 (7.5%) non-Italian nationals. We found that, compared to Italian cases, non-Italian cases were diagnosed at a later date and were more likely to be hospitalised [(adjusted relative risk (ARR)=1.39, 95% confidence interval (CI): 1.33-1.44)] and admitted to ICU (ARR=1.19, 95% CI: 1.07-1.32), with differences being more pronounced in those coming from countries with lower HDI. We also observed an increased risk of death in non-Italian cases from low-HDI countries (ARR=1.32, 95% CI: 1.01-1.75). ConclusionsA delayed diagnosis in non-Italian cases could explain their worse outcomes compared to Italian cases. Ensuring early access to diagnosis and treatment to non-Italians could facilitate the control of SARS-CoV-2 transmission and improve health outcomes in all people living in Italy, regardless of nationality.
ABSTRACT
BackgroundIn February 2020, a locally-acquired COVID-19 case was detected in Lombardia, Italy. This was the first signal of ongoing transmission of SARS-CoV-2 in the country. The outbreak rapidly escalated to a national level epidemic, amid the WHO declaration of a pandemic. MethodsWe analysed data from the national case-based integrated surveillance system of all RT-PCR confirmed COVID-19 infections as of March 24th 2020, collected from all Italian regions and autonomous provinces. Here we provide a descriptive epidemiological summary on the first 62,843 COVID-19 cases in Italy as well as estimates of the basic and net reproductive numbers by region. FindingsOf the 62,843 cases of COVID-19 analysed, 71.6% were reported from three Regions (Lombardia, Veneto and Emilia-Romagna). All cases reported after February 20th were locally acquired. Estimates of R0 varied between 2.5 (95%CI: 2.18-2.83) in Toscana and 3 (95%CI: 2.68-3.33) in Lazio, with epidemic doubling time of 3.2 days (95%CI: 2.3-5.2) and 2.9 days (95%CI: 2.2-4.3), respectively. The net reproduction number showed a decreasing trend starting around February 20-25, 2020 in Northern regions. Notably, 5,760 cases were reported among health care workers. Of the 5,541 reported COVID-19 associated deaths, 49% occurred in people aged 80 years or above with an overall crude CFR of 8.8%. Male sex and age were independent risk factors for COVID-19 death. InterpretationThe COVID-19 infection in Italy emerged with a clustering onset similar to the one described in Wuhan, China and likewise showed worse outcomes in older males with comorbidities. Initial R0 at 2.96 in Lombardia, explains the high case-load and rapid geographical spread observed. Overall Rt in Italian regions is currently decreasing albeit with large diversities across the country, supporting the importance of combined non-pharmacological control measures. Fundingroutine institutional funding was used to perform this work.
