Evolution of Italian COVID-19 epidemiology in the first two years of the pandemic

Recent studies published in medRxiv* The preprint server assessed the lethality and severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during the two years of the SARS-CoV-2 pandemic in Italy.

Background

The first two years of the SARS-CoV-2 pandemic are defined by an ever-evolving epidemiological condition that poses significant challenges to almost every country in the world. Tracking important characteristics such as the potential for severe and fatal consequences and the incidence of infection is greatly hampered by the lack of notification of SARS-CoV-2 infection.

Many features of the temporal variation of CoV disease 2019 (COVID-19) epidemiology during the pandemic remain uncertain due to uncertain levels of undetected SARS-CoV-2 infection. To calculate the burden of COVID-19 and the future risk of SARS-CoV-2 infection, assess the immunity acquired during the first two years of the pandemic and the potential for adverse consequences (such as hospitalization and death). Is important.

About research

In the current study, researchers used a mathematical model of SARS-CoV-2 infection and vaccination guided by genomic and epidemiological monitoring to daily SARS in Italy for the first two years of the COVID-19 pandemic. -Estimated number of CoV-2 infections Data on viral mutations. Specifically, in the context of COVID-19, the team has an infection attack rate, infection confirmation rate, population vulnerabilities to infection, and unfavorable consequences (hospitalization, intensive care unit (ICU) admission, and mortality). Provided an estimate of the potential changes in. Current survey.

Researchers simulate COVID-19 vaccination and infection in Italy between February 21, 2020, the date of detection of the first locally infected SARS-CoV-2 case, and February 20, 2022. Established an age-based probabilistic framework for. Year of simulation. The SARS-CoV-2 ancestral line was circulating in the first two phases, while the alpha, delta, and omicron variants were predominant in phases 3, 4, and 5, respectively.

result

According to the research results, the confirmed rate of SARS-CoV-2 infection between the two SARS-CoV-2 ancestral phases was high. This inference can be due to increased test capacity, improvements to the local reporting system, and the application of rigorous test track and trace methods.

Meanwhile, the authors found a reduction in infection detection during the delta and alpha phases. This finding may have been caused by a variety of factors, including the availability of home testing, self-diagnosis not reported to the monitoring network, reduced contact tracing frequency since 2021, and asymptomatic on augmentation. Caused a marked increase in infection. Of the vaccination initiative.

In fact, COVID-19 vaccination has shifted the prevalence of infections to younger age groups and increased breakthrough infections. Both patterns reduced the overall likelihood of experiencing SARS-CoV-2 symptoms, resulting in an overall reduction in the likelihood that infected people would not be aware that they would seek testing. The infection confirmation rate increased again during the Omicron period. The testing capacity of COVID-19 was significantly expanded during this period due to the increased infection. In addition, voluntary screening has increased as people prepare for rallies during Christmas and New Year holidays.

The team found that the incidence of SARS-CoV-2 ancestral strains, delta, and alpha variants was in the same range, 10-17%, while the incidence of Omicron by February 20, 2022. The rate was significantly higher, that is, 51%. .. Probability of hospitalization, ICU hospitalization, and infection-related mortality due to the combined effects of COVID-19 vaccination, immunity from natural SARS-CoV-2 infection, changes in viral variant characteristics, and better patient management. Is 40 times higher during the period of Omicron dominance compared to the 20-early acute phase.

Current findings highlight the important role that COVID-19 booster vaccination played at the Omicron stage. By the end of February 2022, the authors predicted that 9 out of 10 Italians still protected by vaccination could have received booster shots. As immunity weakens, the booster effect diminishes over time, which may increase the population’s susceptibility to COVID-19 during 2022.

Conclusion

The findings show that despite the significant increase in SARS-CoV-2 cases since the start of 2022, the burden of COVID-19 in Italy is low and the impact on hospitals is acceptable. CoV-2 variants and epidemic patterns bypass existing immunity from natural infections and vaccination and are highlighted by the potential future emergence of new, more contagious or pathogenic viral variants.

In addition, current findings play an important role in the evolution of immunity to SARS-CoV-2 gained from natural infections and vaccination in mitigating the severe clinical outcomes that follow COVID-19 through various stages. I’m emphasizing. A reversal of this pattern may occur in the future if the decline in natural infections and protection by vaccination increase the degree of population vulnerability to COVID-19 again.

*Important Notices

medRxiv publishes unpeer-reviewed preliminary scientific reports and should not be considered definitive, guide clinical / health-related behaviors, or be treated as established information.