Coronavirus, an enveloped virus belonging to the family of Coronaviridae which initially
caused enzootic infections, has shown in the last decades to be capable of crossing
the species barrier causing severe epidemics in humans. A novel flu-like coronavirus,
emerging towards the end of 2019 and subsequently named Severe Acute Respiratory Syndrome
Coronavirus 2 (SARS-CoV-2, the virus that causes Coronavirus Disease 2019 [COVID-19])
has been associated with an epidemic initially focused in Wuhan, China [1]. From there,
SARS-CoV-2 has spread quickly throughout China, infecting many thousands of people
and causing more than 4,500 deaths [2]. However, in a globalize world, it immediately
became well clear that this fearsome infection could not be confined to China only,
but soon it spread to neighboring Asian countries and immediately after to more than
201 countries around the world, where more than 3,200,000 individuals have contracted
SARS-CoV-2 and more than 230,000 of them have deceased (data updated on May 3, 2020)
[2]. On march 11, WHO declared the rapidly spreading coronavirus outbreak a pandemic
and Italy is currently the country with the highest number of cases of SARS-CoV-2
infection after USA and this has generated an unprecedented health and social emergency.
Unfortunately, no standardized therapy does exist for COVID-19 and a number drugs
for the use in patients with life-threatening COVID-19 are currently being investigated
in a number of non-randomized or randomized trials. These agents includes steroids,
chloroquine, antiviral and anti-inflammatory agents [3]. In addition, experiences
from previous coronavirus epidemics indicate that convalescent plasma collected from
recovered COVID-19 patients, containing antibodies specific against SARS-CoV-2 that
can be delivered from donors to patients, could be a potentially effective therapeutic
weapon [4].
Before SARS-CoV-2, the use of convalescent plasma has been investigated, with reported
positive outcomes, in outbreaks of other viral infections, including the 1918 Spanish
H1N1 influenza A pandemic and, more recently, the 2003 Avian H5N1 influenza A epidemic,
the 2003 SARS-CoV-1 epidemic, the 2009-2010 H1N1 influenza pandemic, the 2012 Middle
East Respiratory Syndrome (MERS)-CoV epidemic, and the 2014 Ebola epidemic [5]. Pertaining
to the respiratory CoV infections, a number of studies have been conducted during
the past decade to evaluate the clinical effectiveness of convalescent plasma. A systematic
review and exploratory meta-analysis performed in 2015 identified 32 studies of SARS
coronavirus infection and severe influenza. These studies involved 699 treated patients
and 568 untreated controls [6]. In the pooled analysis of the data, the review revealed
the evidence for a consistent reduction in mortality in the group treated with plasma
therapy compared with that receiving placebo or no therapy (odds ratio, 0.25; 95%
CI:0.14–0.45 with a low degree of heterogeneity: I
2 = 0%) [6]. Only few reports have been published so far on the use of convalescent
plasma in COVID-19 patients. Shen and colleagues reported a case series of 5 critically
ill patients, all receiving convalescent plasma containing SARS-CoV-2 antibodies (titer
> 1:1000) and a neutralization titer greater than 40, administered between day 10
and 22 of admission [7]. Following transfusion, 4 out of 5 patients experienced increases
in viral antibody titers, decreases in SARS-CoV-2 viral loads, and normalization of
temperature and resolution of acute respiratory distress syndrome (ARDS) [7]. Duan
and colleagues presented a series of 10 severely ill COVID-19 patients, all receiving
a 200 mL transfusion of convalescent plasma with high titers of neutralizing antibody
(>1:640) at a median of 16.5 days [8]. The primary endpoint was safety, which was
demonstrated as all patients tolerated plasma transfusion without severe adverse events.
The secondary endpoints included improvement of clinical symptoms and of laboratory
values from day 3 post-infusion. They reported increase neutralizing antibody titer,
oxygen saturation and lymphocyte count and decrease in C-reactive protein, SARS-CoV-2
viral load and lung lesions on radiological examination [8]. Zhang and colleagues
described retrospectively 4 critically ill patients who were transfused with 200-2400
mL of convalescent plasma ranging from day 11 to day 18 of admission [9]. All the
patients (including a pregnant woman) recovered from the SARS-CoV-2 infection. Finally,
Zeng and colleagues tested the role of convalescent plasma in 6 critically end-stage
COVID-19 patients [10]. Although the blood component, which was transfused at a median
of 21.5 days after first detection of viral shedding, led to the discontinuation of
the SARS-CoV-2 shedding by 3 days after infusion, it was not able to improve the survival
in these patients with advanced disease (5/6 and 14/15 deaths in the convalescent
plasma group and control group, respectively). Based on the results of this trial,
the authors concluded the convalescent plasma should be used in an early phase of
the disease to obtain the best effect [10].
Following these first reports on the successful use of convalescent plasma in COVID-19
patients in China and considering the efficacy of this treatment in previous severe
viral epidemics and the absence of standardized treatments, the Food and Drug Administration
(FDA) approved the use of convalescent to treat critically ill patients on 26 march
2020 and this action has fueled the planning of several trials. A research performed
on May 4, 2020 on clinicaltrials.gov (https://clinicaltrials.gov) with the terms “convalescent
plasma and COVID-19” showed 38 active ongoing trials on the use of convalescent plasma
in COVID-19 patients, heterogeneous in term of study design and outcomes’ criteria:
14 of them are randomized versus other approaches (2 studies versus placebo, 5 studies
versus standard fresh frozen plasma and 7 versus various pharmacologic agents including
hydroxychloroquine and antiviral drugs). Also our group, in collaboration with University
of Pavia, has given a contribute to this research. Indeed, considering the dramatic
situation and the high lethality rate of COVID-19 in Italy, we have planned an interventional
single-arm trial (NCT04321421) to produce hyperimmune plasma for treating critical
patients with COVID-19. The results of these numerous trials are greatly awaited as
they will permit to respond to the many still unanswered issues regarding convalescent
plasma, including donors’ selection (i.e., age, gender, diagnosis of SARS-Cov-2 infection
and of recovery, anti-SARS-CoV-2 antibody titer required for plasma donation), plasma
collection and biologic qualification (number, volume and frequency of donations,
infectious disease markers and pathogen inactivation) and treatment and disease characteristics
(i.e., dose and timing of convalescent plasma infused and stage of the disease at
which to start convalescent plasma treatment).
There is currently great interest towards the use of passive immunotherapy by means
of transfusion of convalescent plasma from recovered COVID-19 patients documented
the high number of ongoing trials and of reviews/perspectives/commentaries published
every day. The results of such trials will help us to elucidate the still unanswered
issues related listed above and related to convalescent plasma collection, biologic
validation and treatment modalities. Meanwhile, the data arising from previous coronaviruses
epidemics and from COVID-19 case series, although limited, strongly encourage clinicians
and investigators to treat COVID-19 patients, particularly at an early stage of the
disease, also with convalescent plasma in the frame of registered protocols.
Declaration of competing interest
None