Passive immunotherapy through plasma infusion of convalescent subjects - convalescent plasma - or "hyperimmune" plasma was one of the most widespread and effective anti-infective treatments in the pre-antibiotic era and one of the founding pillars of immunology, and has also been used during the SARS (2002-2003) and Ebola (2014-2016) viral epidemy for which there were no alternative immunoprophylactic or therapeutic interventions.

To date, there are not proven etiological therapies for SARS-CoV-2 infection, the agent responsible for the disease called Covid-19. Among those subjected to clinical studies during the current epidemic in China, hyperimmune plasma appears to be one of the most rational and promising.

The objective of this study will be to evaluate the efficacy and safety of the hyperimmune plasma administered add-on to the anti-Covid-19 treatment (standard therapy) according to clinical practice in patients with severe Covid-19 infection, compared to patients with severe Covid-19 infection treated only with standard therapy.

Passive immunotherapy through plasma infusion of convalescent subjects - convalescent plasma - or "hyperimmune" plasma was one of the most widespread and effective anti-infective treatments in the pre-antibiotic era and one of the founding pillars of immunology. Immunoprophylaxis represents an irreplaceable protection for post-exposure prevention of several viral infections such as measles, hepatitis B and rabies. Recently, the use of convalescent plasma for therapeutic purposes has been re-evaluated during the SARS (2002-2003) and Ebola (2014-2016) epidemic caused by serious viral infections for which there were no immunoprophylactic or therapeutic interventions. alternative. The results of these experimental interventions, despite the limited number and the often anecdotal character, have shown promise even if not conclusive. In the case of SARS, the first human respiratory disease caused by a Coronavirus, treatment with convalescent plasma was associated with a 23% reduction in mortality and with the best results if administered at an early stage of the disease. In addition, all the evidence available in the literature has confirmed the safety of convalescent plasma treatments, in line with what has already been observed in the transfusion practice with Fresh Frozen Plasma.

As is known, there are currently no proven etiological therapies to combat SARS-CoV-2 infection, the agent responsible for the disease called Covid-19. Among those subjected to clinical studies during the current epidemic in China, hyperimmune plasma appears to be one of the most rational and promising.

Waiting for the numerous clinical trials underway especially in Asia and accessible on the website http://apps.who.int/trialsearch/default.aspx to define if and to what extent this therapeutic contribution improves the prognosis of patients suffering from serious forms of infections from SARS-Co-2, the clinical guidelines of the People's Republic of China, already provide for the use of hyperimmune plasma with the indication "in rapidly progressive disease, severe and very severe form" and by the FDA .

As regards the technical protocols for the preparation of hyperimmune plasma for clinical use in the literature, precise references are available in particular for the preparation, qualification, viral inactivation and dosage of hyperimmune plasma for the treatment of viral epidemic infections such as MERS and Ebola and which can also be validated and used for the preparation of plasma from convalescent patients for Covid-19.

From the above, the objective of this study will be to evaluate the efficacy and safety of the hyperimmune plasma administered add-on to the anti-Covid-19 treatment (standard therapy) according to clinical practice in patients with severe Covid-19 infection, compared to patients with severe Covid-19 infection treated only with standard therapy.

Inclusion Criteria:

• inclusion criteria for donors: null-gravid, with a negative history of transfusion of blood components; possibility to sign the informed consent
• inclusion criteria for Covid-19 infected patients: serious Covid-19 infection, possibility to sign the informed consent (also through the legal tutor)

Exclusion Criteria:

• exclusion criteria for donors: presence of pregnancy, recent history of transfusion of blood components, < 18 years.
• exclusion criteria for Covid-19 infected patients: non serious Covid-19 infection, impossibility to sign the informed consent (also through the legal tutor)