Problem to be addressed: In December 2019, the Wuhan Municipal Health Committee (Wuhan,
China) identified an outbreak of viral pneumonia cases of unknown cause. Coronavirus RNA was
quickly identified in some of these patients.This novel coronavirus has been designated
SARS-CoV-2, and the disease caused by this virus has been designated COVID-19.Outbreak
forecasting and mathematical modelling suggest that these numbers will continue to rise [1]
in many countries over the coming weeks to months.Global efforts to evaluate novel antivirals
and therapeutic strategies to treat COVID-19 have intensified. There is an urgent public
health need for rapid development of novel interventions. At present, there is no specific
antiviral therapy for coronavirus infections.

Passive immunization:Passive immunization consists in the transfer of antibodies from
immunized donor to non-immunized individual in order to transfer transient protection against
an infective agent. A physiological example of passive immunization is the transfer of
maternal IgG antibodies to the foetus through the placenta to confer humoral protection to
newborns in the first years of life. Passive immunization differs from active immunization in
which the patient develops their own immune response following contact with the infective
agent or vaccine.

Known potential risks and benefits: There is a theoretical risk of antibody-dependent
enhancement of infection (ADE) through which virus targeted by non-neutralizing antibodies
gain entry into macrophages. Another theoretical risk is that antibody administration to
those exposed to SARS-CoV-2 may avoid disease but modify the immune response such that those
individuals mount attenuated immune responses, which would leave them vulnerable to
subsequent re-infection. Finally, there are risks associated with any transfusion of plasma
including transmission of blood transmitted viruses (e.g. HIV, HBV, HCV, etc.), allergic
transfusion reactions, including anaphylaxis, febrile non hemolytic transfusion reaction,
transfusion related acute lung injury (TRALI), transfusion associated cardiac overload
(TACO), and hemolysis should ABO incompatible plasma be administered. Potential benefits of
COVID-19 convalescent plasma include improved survival, improvement in symptoms, decreased
risk in intubation for mechanical ventilation, decrease risk of intensive care unit (ICU)
admission, shortened hospitalization time and suppression of viral load.

Mechanism of action: Transfusion of apheresis frozen plasma (AFP) from COVID-19 convalescent
patients allows the transfer of donor neutralizing antibodies directed against SARS-CoV2
antigens to the recipient, thus allowing the generation of passive immunization. Naturally
produced human antibody are polyclonal, meaning they are directed against a variety of
different viral antigens and epitopes allowing for a general neutralizing effect against the
virus rather than focussing on a specific target. Administration of convalescent plasma has
been associated with rapid decrease in viral load. It is also possible that passive
immunization contributes to improved cell-mediated immunity by favoring the phagocytosis and
presentation of viral antigens to host T cells.

Participant recruitment:Only hospitalized COVID-19 patients are eligible so recruitment
efforts will be focused on identified consecutive patients admitted to hospital with acute
COVID-19 infection. No other external recruitment efforts are planned. At each participating
hospital, a process for identifying patients with COVID-19 will be established.

Donor recruitment for Canadian sites: Recovered COVID-19 patients will be identified as
potential donors in collaboration with provincial public health services, local health
authorities, and individual co-investigators involved in the study. Potential donors may also
be recruiting following self-identification on the routine donor questionnaire or through
social media. They will be contacted by phone and invited to participate in the program as
potential donors. After obtaining verbal consent and reviewing donor selection criteria,
eligible participants will be directed to a Héma-Québec collection or Canadian Blood Services
apheresis collection site in their area to donate.

Criteria for donors: All donors will need to meet the criteria set forth in the Manual of
donor selection criteria in use at Héma-Québec or Canadian Blood ServicesIn addition, donors
will require:

- Prior diagnosis of COVID-19 documented by a PCR test at time of infection or by positive
anti-SARS-CoV-2 serology following infection

- Male donors, or female donors with no pregnancy history or with negative anti-HLA
antibodies

- At least 6 days since last plasma donation

- Provided informed consent

- A complete resolution of symptoms at least 14 days prior to donation

Donor recruitment for United States sites: Recovered COVID-19 patients are being recruited
through the New York Blood Center and Weill Cornell Medicine in separate protocols. Potential
donors can self-refer via websites but also be referred by physicians or identified via the
medical record system. Only donors with laboratory-confirmed history of COVID-19 will be
screened. After providing consent and reviewing FDA and NYBC donor eligibility criteria,
donors are screened for the presences of SARS-CoV-2 virus in the nasopharynx if screening
within 14 days of complete resolution in accordance with current FDA guidance. Criteria for
donation are subject to change based on future revision of FDA guidance. Those found to be
eligible will be referred to NYBC for donation.

Criteria for donors:

- Provision of informed consent

- Aged 18 to 70 years. Donors are not longer eligible after their 71st birthday.

- Documented molecular diagnosis of SARS-CoV-2 by RT-PCR by nasopharyngeal swab,
oropharyngeal swab, or sputum or detection of anti-SARS-CoV-2 IgG in serum.

- Complete resolution of COVID-19 symptoms at least 14 days prior to donation

- Not currently pregnant or pregnant within 6 weeks by self-report

- Male donors, or females with no pregnancy history or with negative anti-HLA antibodies

- Meets blood donor criteria specified by NYBC, which is consistent with FDA regulations.

Donors will be allowed to donate every 7 days. The following information will be collection
from donors: ABO group, sex, age, date of onset of symptoms (when available), date of
resolution of symptoms (when available), CCP collection date(s).

Randomization procedures: Patients will be randomized in a 2:1 ratio (convalescent plasma vs
standard of care). Patients will be randomized using a secure, concealed, computer-generated,
web-accessed randomization sequence. Randomization will be stratified by centre and age (<60
and ≥ 60 years). Within each stratum, variable permuted block sized will be used. This
approach will ensure that concealment of the treatment sequence is maintained.

Duration of follow-up: Subjects will be followed daily until hospital discharge or death.
Patients discharged from hospital before Day 30 will be contacted by telephone on Day 30 ± 3
days to ascertain any AEs, vital status (dead/alive), hospital readmission and need for
mechanical ventilation after discharge. Patients discharged from hospital will be contacted
at Day 90+/- 7 days to determine vital status. Patients with a prolonged hospital admission
will be censored at Day 90. The local study coordinator will collect all study data and
record the data in the electronic CRF or paper CRF as per study procedures for each site.

Duration of study: For an individual subject, the study ends 90 days after randomization. The
overall study will end when the last randomized subject has completed 90 day follow-up. We
estimate that all patient will be enrolled in a period of 6 months, data on the primary
endpoint will be available 30 days after last patient enrollment and data on all secondary
endpoints will be available after 90-day from last patient enrollment.

Sample size considerations: Assuming a baseline risk of intubation or death of 30% in
hospitalized patients with standard of care, a sample size of 1200 (800 in the convalescent
plasma arm, and 400 in the standard of care arm) would provide 80% power to detect a relative
risk reduction of 25% with convalescent plasma therapy using a 2-tailed test at level α =
0.05 and a 2:1 randomization.

Interim analysis: A single interim analysis is planned when the primary outcome (intubation
or mortality at 30 days) is available for 50% of the target sample. An O'Brien-Fleming
stopping rule will be used at that time, but treated as a guideline, so there is minimal
impact on the threshold for statistical significance for the final significance test of the
primary outcome. A DSMB will monitor ongoing results to ensure patient well-being and safety
as well as study integrity. The DSMB will be asked to recommend early termination or
modification only when there is clear and substantial evidence of a treatment difference.

Final analysis plan: The primary analysis will be based on the intention-to-treat population
which will include data from all individuals who have been randomized. Outcomes will be
attributed to the arm to which individuals were randomized irrespective of whether they
received the planned intervention (e.g. plasma from a convalescent COVID-19 donor).