Impact of SARS-CoV-2 Omicron and Delta variants in patients requiring intensive care unit (ICU) admission for COVID-19, Northern Italy, December 2021 to January 2022.

This multicenter observational study included 171 COVID-19 adult patients hospitalized in the ICUs of nine hospitals in Lombardy (Northern Italy) from December, 1st 2021, to February, 9th 2022. During the study period, the Delta/Omicron variant ratio of cases decreased with a delay of two weeks in ICU patients compared to that in the community; a higher proportion of COVID-19 unvaccinated patients was infected by Delta than by Omicron whereas a higher rate of COVID-19 boosted patients was Omicron-infected. A higher number of comorbidities and a higher comorbidity score in ICU critically COVID-19 inpatients was positively associated with the Omicron infection as well in vaccinated individuals. Although people infected by Omicron have a lower risk of severe disease than those infected by Delta variant, the outcome, including the risk of ICU admission and the need for mechanical ventilation due to infection by Omicron versus Delta, remains uncertain. The continuous monitoring of the circulating SARS-CoV-2 variants remains a milestone to counteract this pandemic.

Genomic surveillance of SARS-CoV-2 positive passengers on flights from China to Italy, December 2022.

With numbers of COVID-19 cases having substantially increased at the end of 2022 in China, some countries have started or expanded testing and genomic surveillance of travellers. We report screening results in Italy in late December 2022 of 556 flight passengers in provenance from two Chinese provinces. Among these passengers, 126 (22.7%) tested SARS-CoV-2 positive. Whole genome sequencing of 61 passengers' positive samples revealed Omicron variants, notably sub-lineages BA.5.2.48, BF.7.14 and BQ.1.1, in line with data released from China.

Safety and immunogenicity of synchronous COVID19 and influenza vaccination.

Given the ongoing COVID19 pandemic, the decline in serological response since dose 2, and the upcoming flu season, COVID19 vaccines will increasingly be administered in combination with vaccines against seasonal pathogens. It is of interest to confirm that concurrent vaccination against influenzavirus has no negative impact on serological response to SARS CoV-2. Anti-Spike IgG and Anti-Receptor Binding Domain (RBD) Neutralizing Antibodies (NAb) in serum  was assessed in 64 immunocompetent healthcare workers (HCW) before and 14 days post the third dose of BNT162b2 vaccine (Comirnaty®, Pfizer/BioNTech) or BNT162b2 plus quadrivalent flu vaccine (Vaxigript Tetra ®Sanofi Pasteur) on the same day. We report here safety and efficacy of combined BNT162b2 and flu vaccine in 64 healthcare workers at a single institution. No differences were found in adverse events or anti-Spike antibody levels.

Breakthrough Infections of E484K-Harboring SARS-CoV-2 Delta Variant, Lombardy, Italy.

The Delta variant of concern of severe acute respiratory syndrome coronavirus 2 is dominant worldwide. We report a case cluster caused by Delta sublineage B.1.617.2 harboring the mutation E484K in Italy during July 11-July 29, 2021. This mutation appears to affect immune response and vaccine efficacy; monitoring its appearance is urgent.

Symptomatic SARS-CoV-2 infections after full schedule BNT162b2 vaccination in seropositive healthcare workers: a case series from a single institution.

We report 11 cases of SARS-CoV-2 infection in healthcare workers (HCW) naïve for COVID-19 and seropositive after the second dose of the BNT162b2 mRNA vaccine. Based on voluntary-based surveillance, they tested positive for different strains of SARS-CoV-2, as Spike gene sequencing showed. Five of them reported mild symptoms. Given the risk for SARS-CoV-2 introduction from asymptomatic vaccinees, this case series suggests the need to continue nasopharyngeal screening programmes.