Severe acute respiratory syndrome coronavirus (SARS‐CoV)‐2 has spread worldwide, leading the World Health Organization (WHO) to declare a pandemic, on 11 March 2020. Variants of concern have appeared at regular intervals—Alpha, Beta, Gamma, Delta, and now Omicron. Omicron variant, first identified in Botswana in November 2021, is rapidly becoming the dominant circulating variant. In this review, we provide an overview regarding the molecular profile of the Omicron variant, epidemiology, transmissibility, the impact on vaccines, as well as vaccine escape, and finally, we report the pharmacological agents able to block the endocellular entry of SARS‐CoV‐2 or to inhibit its viral replication. The Omicron has more than 50 mutations, of which the spike protein has 26–35 amino acids different from the original SARS‐CoV‐2 virus or the Delta, some of which are associated with humoral immune escape potential and greater transmissibility. Omicron has a significant growth advantage over Delta, leading to rapid spread with higher incidence levels. The disease so far has been mild compared to the Delta. The two vaccination doses offer little or no protection against Omicron infection while the booster doses provide significant protection against mild illness and likely offer even greater levels of protection against serious illness. Recently, new oral antiviral agents such as molnupiravir and paxlovid have been approved and represent important therapeutic alternatives to antiviral remdesivir. In addition, monoclonal antibodies such as casirivimab/imdevimab bind different epitopes of the spike protein receptor; is this class of drugs effective against the Omicron variant? However, more research is needed to define whether Omicron is indeed more infectious and whether the vaccines, monoclonal antibodies, and antivirals currently available are effective.

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Background Infections due to drug-resistant herpes simplex viruses (HSV) represent an important clinical concern, especially in immunocompromised patients. The present study was aimed at detecting acyclovir (ACV) susceptibility in HSV clinical samples. Methods A total of 13 HSV-positive clinical samples (5 HSV-1 and 8 HSV-2) recovered from patients (1 immunocompromised and 12 of unknown immune status) were included in the study. The genotypic analysis involved an initial UL23 (thymidine kinase) gene sequencing, followed by a confirmatory phenotypic assay using plaque reduction technique. Results Two novel amino acid changes, A37V and H283N, were detected in HSV-1 positive clinical samples, which were found to be susceptible to acyclovir (half maximal effective concentration = 1.5 μM) by plaque reduction assay. Conclusions These two novel amino acid changes could be therefore considered as natural polymorphisms, a phenomenon widely associated with the HSV-UL23 gene.

The global COVID-19 pandemic is underway. In recent weeks, several countries throughout the globe, and particularly in Europe, have experienced an exponential increase in the number of individuals infected with COVID-19, probably induced by a new variant of SARS-CoV-2, called the "Omicron variant." Mass vaccination against COVID-19 continues worldwide. Are authorized mRNA vaccines effective against the new Omicron variant? Recently, several pharmaceutical companies have developed oral antiviral pills against SARS-CoV-2, i.e., molnupiravir and paxlovid, that inhibit SARS-CoV-2 viral replication by acting on the RNA polymerase of SARS-CoV. In pre-registration clinical trials, molnupiravir and paxlovid have shown excellent clinical efficacy results, but what impact will these new oral antiviral agents have against pandemic COVID-19? In what specific clinical situations are they preferred over other antivirals such as remdesivir? In this brief review, we explore these important aspects.

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