## 4 Discussion  
In the context of the current COVID-19 pandemic, physicians treating patients with psoriasis are tasked with challenging decisions when initiating immunosuppressive therapy or altering the existing regimens for their patients. Moreover, they must be ready to understand the needs of patients undergoing vaccination and be aware of the reciprocal effects of psoriasis and SARS-CoV-2 infection. Relationships between COVID and psoriasis can be synthesized as follows:  
Most of the existing evidence is based on spontaneous case series, and although data from literature globally indicate no significant increase of the risk for severe COVID-19 evolution in psoriasis patients, it is hard to evaluate which biological agent is safer for COVID-19. However, from the current unclassified research, biologics do not seem to have a significant impact on the COVID-19 course. Regardless of which biological agents have been used, patients in biologics treatment seem to be not at higher risk for severe COVID complications. According to the recommendations of the major global dermatological associations [108; 109; 110], asymptomatic patients in close contact with a confirmed or probable COVID-19 case in the last 14 days can continue biologic therapy. It is advisable to discontinue or postpone biological treatment in symptomatic patients with confirmed SARS-CoV-2 infections until COVID-19 is completely resolved. For all candidates undergoing biological treatment, it is advisable to carefully assess the balance between benefits and risks of treatment for each patient. The National Psoriasis Foundation COVID-19 Task Force, in the last version of guidance for the management of psoriatic disease during the pandemic has reported that patients not infected with SARS-CoV-2 should continue biologics for psoriasis in most cases. Shared decision-making process between clinician and patient is recommended to guide discussions about the use of systemic therapies during the pandemic [58]. Scientific dermatological associations recommend that psoriasis patients with asymptomatic SARS-CoV-2 infection and at low risk for severe COVID-19 evolution (younger age, no systemic comorbidities) should continue their biological therapy. For high-risk patients (older age, with comorbidities, or metabolic disorders such as diabetes and obesity), the decision of discontinuing the treatment should be made case on case, through the balancing of benefits and risks, and the risk of disease relapse and retreatment failure should be taken into consideration too [41]. Similarly, Appremilast seems to be a safe treatment for psoriasis patients with COVID-19, thus at this moment it is not indicated to suspend the on-going treatment in psoriasis patients who get SARS-CoV-2 infection. * Conversely, as the impact of MTX or CsA on COVID-19 infection is still to be cleared, despite they are commonly used immunosuppressive agent for psoriasis, studies focusing on these drugs on SARS-CoV-2 infection or COVID-19 evolution in psoriasis patients under treatment are few and inconclusive. Further research in this field is warranted and needed, before giving specific recommendation on continuation of their use in psoriatic patients affected by COVID-19. * Although psoriatic patients have no increased risk of evolving toward severe forms of COVID-19 compared to the general population, they are frail subjects with respect to SARS-COV-2 infection which can favor the release of psoriasis clinically in remission, or favor its onset in predisposed patients or condition the appearance of different psoriasis phenotypes (e.g., pustular forms). * Vaccination still represents the most effective measure to prevent the development of serious form of COVID-19 in psoriasis patients who should be advised to be vaccinated without discontinuuing their biological treatment.