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Background: The COVID-19 pandemic has been a health emergency with a significant impact on the world due to its high infectiousness. The disease, primarily identified in the lower respiratory tract, develops with numerous clinical symptoms affecting multiple organs and displays a clinical finding of anosmia. Several authors have investigated the pathogenetic mechanisms of the olfactory disturbances caused by SARS-CoV-2 infection, proposing different hypotheses and showing contradictory results. Since uncertainties remain about possible virus neurotropism and direct damage to the olfactory bulb, we investigated the expression of SARS-CoV-2 as well as ACE2 receptor transcripts in autoptic lung and olfactory bulb tissues, with respect to the histopathological features. Methods: Twenty-five COVID-19 olfactory bulbs and lung tissues were randomly collected from 200 initial autopsies performed during the COVID-19 pandemic. Routine diagnosis was based on clinical and radiological findings and were confirmed with post-mortem swabs. Real-time RT-PCR for SARS-CoV-2 and ACE2 receptor RNA was carried out on autoptic FFPE lung and olfactory bulb tissues. Histological staining was performed on tissue specimens and compared with the molecular data. Results: While real-time RT-PCR for SARS-CoV-2 was positive in 23 out of 25 lung samples, the viral RNA expression was absent in olfactory bulbs. ACE2-receptor RNA was present in all tissues examined, being highly expressed in lung samples than olfactory bulbs. Conclusions: Our finding suggests that COVID-19 anosmia is not only due to neurotropism and the direct action of SARS-CoV-2 entering the olfactory bulb. The mechanism of SARS-CoV-2 neuropathogenesis in the olfactory bulb requires a better elucidation and further research studies to mitigate the olfactory bulb damage associated with virus action. [ABSTRACT FROM AUTHOR]

The successful deployment of safe and effective vaccines against coronavirus disease 2019 (COVID-19) has been crucial in reducing the global disease burden. Owing to the need for vaccination series over time, continuous observational studies are needed to estimate the COVID-19 vaccine response in real-world conditions. In particular, the detection, assessment, and understanding of adverse effects following immunization (AEFI) with a COVID-19 vaccine are crucial to better address vaccination strategies. Therefore, this study aimed to investigate the risk of repeated AEFI post-administration of a booster dose of mRNA COVID-19 vaccine in a sample of healthcare workers (HCWs) in an Italian teaching hospital. The data on any local and systemic AEFI were studied in multivariate Poisson regression analyses to model the association between the incidence of each postvaccination symptom and its prior reporting after the administration of the previous doses. Overall, compared with the primary vaccination series, the majority of post-third dose AEFI were less reported. The results from multivariable models showed that the likelihood of reporting an AEFI after the third dose was higher in those who experienced the same postvaccination symptom after the second dose (all AEFI except for itch at injection site) and, although not significant for all AEFI, after the first dose. Any associations with age, gender, smoking habits, previous SARS-CoV-2 infection and other characteristics, as well as the health impact of AEFI were also assessed. Taken together, the results from this research support reframe AEFI symptoms as signals of a robust postvaccination reaction as well as of common vaccine response, and they add important data to inform booster vaccination strategies in HCWs and, extensively, in the adult population. [ABSTRACT FROM AUTHOR]

This longitudinal observational study investigated the risk of breakthrough SARS-CoV-2 infection up to 6 months after a booster dose of an mRNA COVID-19 vaccine in infection-naïve vs. previously infected healthcare workers (HCWs), and whether this difference varied over time. A Cox proportional hazard regression model with Aalen's additive analysis was fitted to examine the association between the risk of infections and predictor variables. Overall, we observed an incidence rate of 2.5 cases per 1000 person-days (95% confidence interval [CI] 2.0–3.0), which dropped at 0.8 per 1000 person-days (95% CI 0.3–2.0) in recipients with prior SARS-CoV-2 infection. The fitted analysis indicated an adjusted hazard ratio of 0.32 (95% CI 0.13–0.80; p-value = 0.01) for those with hybrid immunity with a slope that became steeply negative roughly starting from day 90. No difference was seen according to participants' smoking habits. Characteristics of infected HCWs were also described. Our study quantifies the time-varying effects of vaccine-induced and hybrid immunity after the booster dose (during the Omicron variant predominance in Italy) and observed that the protection waned more rapidly in infection-naïve recipients starting from the third month. The results add important evidence that can be used to inform COVID-19 vaccination strategies. [ABSTRACT FROM AUTHOR]

First, the author stated that "The SARS-CoV-2 spike protein has a sequence like neurotoxins, capable of binding nicotinic acetylcholine receptors (nAChR). 33833618 10 Petrillo M., Brogna C., Cristoni S., Querci M., Piazza O., Van den Eede G. Increase of SARS-CoV-2 RNA load in faecal samples prompts for rethinking of SARS-CoV-2 biology and COVID-19 epidemiology. 34914115 9 Li C.X., Chen J., Lv S.K., Li J.H., Li L.L., Hu X. Whole-transcriptome RNA sequencing reveals significant differentially expressed mRNAs, miRNAs, and lncRNAs and related regulating biological pathways in the peripheral blood of COVID-19 patients. 32823591 3 Cafiero C., Micera M., Re A., Postiglione L., Cacciamani A., Schiavone B., Benincasa G., Palmirotta R. Could Small Neurotoxins-Peptides be Expressed during SARS-CoV-2 Infection?. [Extracted from the article]