Because the new cases of Covid-19 are much more than those traced: the alarm of the ISS

In this phase characterized by the circulation of highly transmissible Covid variants “there has probably been a sharp increase in the number of people who have had an infection that has not been notified to the surveillance systems for reasons related to underdiagnosis or ‘self-diagnosis’ phenomena”.

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The percentage of Covid reinfections out of the total reported cases was 8.4% in the last week, an increase compared to the previous week (7.5%). This is what emerges from the extended report published by the Higher Institute of Health in which it is emphasized that from 24 August 2021 to 22 June 2022 556,406 cases of reinfection were reported, equal to 4.0% of the total number of cases notified.

The analysis of the risk of reinfection starting from 6 December 2021 (the reference date for the start of the diffusion of the Omicron variant) shows a increased risk in non-vaccinated against Covid, in women and in younger age groups.

The ISS also explains that the new cases of Covid are actually many more than those reported daily in the bulletin. This is because in this phase of the Covid trend in Italy, characterized by the circulation of highly transmissible variants, “there has probably been a sharp increase in the share of people who have had an infection not notified to the surveillance systems for reasons related to phenomena from underdiagnosis or ‘self-diagnosis’ “. And this could lead to an underestimation of the incidence rate, and therefore of the relative risk, and vaccination efficacy.

The effectiveness of the vaccine (percentage reduction of the risk in vaccinated over unvaccinated) in the period of Omicron prevalence in preventing infections is equal to 54% in those who have had the booster dose (40% in 90 days from the completion of the vaccination cycle, 31% between 91 and 120 days, and 46% over 120 days). On severe disease it is 86% in vaccinated with a booster dose (69% in vaccinated with a full course for less than 90 days, 68% for 91 and 120 days, and 71% for more than 120 days).

Among the other data that emerged in the latest ISS report,increased number of reported cases and hospitalizations while hospitalizations in intensive care and deaths are still decreasing. The percentage of cases among health workers compared to the rest of the population decreased compared to the previous week (2.4%).

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