COVID-19 Evidence Alerts
from McMaster PLUSTM

Current best evidence for clinical care (more info)

Treatment Valk SJ, Piechotta V, Chai KL, et al. Convalescent plasma or hyperimmune immunoglobulin for people with COVID-19: a rapid review. Cochrane Database Syst Rev. 2020 May 14;5:CD013600. doi: 10.1002/14651858.CD013600.

BACKGROUND: Convalescent plasma and hyperimmune immunoglobulin may reduce mortality in patients with respiratory virus diseases, and are currently being investigated in trials as a potential therapy for coronavirus disease 2019 (COVID-19). A thorough understanding of the current body of evidence regarding the benefits and risks is required.  OBJECTIVES: To assess whether convalescent plasma or hyperimmune immunoglobulin transfusion is effective and safe in the treatment of people with COVID-19.

SEARCH METHODS: The protocol was pre-published with the Center for Open Science and can be accessed here:  We searched the World Health Organization (WHO) COVID-19 Global Research Database, MEDLINE, Embase, Cochrane COVID-19 Study Register, Centers for Disease Control and Prevention COVID-19 Research Article Database and trials registries to identify ongoing studies and results of completed studies on 23 April 2020 for case-series, cohort, prospectively planned, and randomised controlled trials (RCTs).

SELECTION CRITERIA: We followed standard Cochrane methodology and performed all steps regarding study selection in duplicate by two independent review authors (in contrast to the recommendations of the Cochrane Rapid Reviews Methods Group). We included studies evaluating convalescent plasma or hyperimmune immunoglobulin for people with COVID-19, irrespective of disease severity, age, gender or ethnicity. We excluded studies including populations with other coronavirus diseases (severe acute respiratory syndrome (SARS) or Middle East respiratory syndrome (MERS)) and studies evaluating standard immunoglobulins.

DATA COLLECTION AND ANALYSIS: We followed recommendations of the Cochrane Rapid Reviews Methods Group regarding data extraction and assessment. To assess bias in included studies, we used the assessment criteria tool for observational studies, provided by Cochrane Childhood Cancer. We rated the certainty of evidence using the GRADE approach for the following outcomes: all-cause mortality at hospital discharge, improvement of clinical symptoms (7, 15, and 30 days after transfusion), grade 3 and 4 adverse events, and serious adverse events.  MAIN RESULTS: We included eight studies (seven case-series, one prospectively planned, single-arm intervention study) with 32 participants, and identified a further 48 ongoing studies evaluating convalescent plasma (47 studies) or hyperimmune immunoglobulin (one study), of which 22 are randomised. Overall risk of bias of the eight included studies was high, due to: study design; small number of participants; poor reporting within studies; and varied type of participants with different severities of disease, comorbidities, and types of previous or concurrent treatments, including antivirals, antifungals or antibiotics, corticosteroids, hydroxychloroquine and respiratory support. We rated all outcomes as very low certainty, and we were unable to summarise numerical data in any meaningful way. As we identified case-series studies only, we reported results narratively. Effectiveness of convalescent plasma for people with COVID-19 The following reported outcomes could all be related to the underlying natural history of the disease or other concomitant treatment, rather than convalescent plasma. All-cause mortality at hospital discharge All studies reported mortality. All participants were alive at the end of the reporting period, but not all participants had been discharged from hospital by the end of the study (15 participants discharged, 6 still hospitalised, 11 unclear). Follow-up ranged from 3 days to 37 days post-transfusion. We do not know whether convalescent plasma therapy affects mortality (very low-certainty evidence).  Improvement of clinical symptoms (assessed by respiratory support) Six studies, including 28 participants, reported the level of respiratory support required; most participants required respiratory support at baseline. All studies reported improvement in clinical symptoms in at least some participants. We do not know whether convalescent plasma improves clinical symptoms (very low-certainty evidence). Time to discharge from hospital Six studies reported time to discharge from hospital for at least some participants, which ranged from four to 35 days after convalescent plasma therapy.  Admission on the intensive care unit (ICU) Six studies included patients who were critically ill. At final follow-up the majority of these patients were no longer on the ICU or no longer required mechanical ventilation. Length of stay on the ICU Only one study (1 participant) reported length of stay on the ICU. The individual was discharged from the ICU 11 days after plasma transfusion. Safety of convalescent plasma for people with COVID-19 Grade 3 or 4 adverse events  The studies did not report the grade of adverse events after convalescent plasma transfusion. Two studies reported data relating to participants who had experienced adverse events, that were presumably grade 3 or 4. One case study reported a participant who had moderate fever (38.9 °C). Another study (3 participants) reported a case of severe anaphylactic shock. Four studies reported the absence of moderate or severe adverse events (19 participants). We are very uncertain whether or not convalescent plasma therapy affects the risk of moderate to severe adverse events (very low-certainty evidence). Serious adverse events One study (3 participants) reported one serious adverse event. As described above, this individual had severe anaphylactic shock after receiving convalescent plasma. Six studies reported that no serious adverse events occurred. We are very uncertain whether or not convalescent plasma therapy affects the risk of serious adverse events (very low-certainty evidence).  AUTHORS' CONCLUSIONS: We identified eight studies (seven case-series and one prospectively planned single-arm intervention study) with a total of 32 participants (range 1 to 10). Most studies assessed the risks of the intervention; reporting two adverse events (potentially grade 3 or 4), one of which was a serious adverse event. We are very uncertain whether convalescent plasma is effective for people admitted to hospital with COVID-19 as studies reported results inconsistently, making it difficult to compare results and to draw conclusions. We identified very low-certainty evidence on the effectiveness and safety of convalescent plasma therapy for people with COVID-19; all studies were at high risk of bias and reporting quality was low. No RCTs or controlled non-randomised studies evaluating benefits and harms of convalescent plasma have been completed. There are 47 ongoing studies evaluating convalescent plasma, of which 22 are RCTs, and one trial evaluating hyperimmune immunoglobulin. We will update this review as a living systematic review, based on monthly searches in the above mentioned databases and registries. These updates are likely to show different results to those reported here.

Discipline / Specialty Area Score
Family Medicine (FM)/General Practice (GP)
General Internal Medicine-Primary Care(US)
Hospital Doctor/Hospitalists
Internal Medicine
Infectious Disease
Public Health
Intensivist/Critical Care
Comments from MORE raters

Family Medicine (FM)/General Practice (GP) rater

It will be interesting to see an update including still ongoing RCTs. For now, the results are uncertain.

Family Medicine (FM)/General Practice (GP) rater

There is nothing much for the clinical practice from the number and types of studies available. However, it is encouraging and enlightening to know that 47 ongoing studies of which 22 are RCTs are evaluating the treatment.

General Internal Medicine-Primary Care(US) rater

It's good to know what we don't know.

General Internal Medicine-Primary Care(US) rater

This article is very timely. However, I suspect most knowledgeable clinicians know that there is no rigorous data on the utility of convalescent plasma or hyperimmune immunoglobulin. Future reports should be more useful.

Hospital Doctor/Hospitalists rater

As a hospitalist in the COVID era, we are desperate for anything that works. The theory that neutralizing antibodies from someone who has recovered from COVID would aid other patients can be applied from experience with rabies, flu, Ebola and many other diseases. However there is some risk that there could be harm; these patients have significant vascular events that this could make worse and there always is risk of anaphylaxis from the plasma itself. This Cochrane review covers only 32 patients of various levels of illness and all non randomized designs; only 6 of the 8 trials reported on side effects (one fever, one anaphylaxis) and 17 of the 32 were either still in hospital (6) or had unclear status. Fortunately this is being studied more rigorously now all over the world ( has 80 trials as of this writing), so hopefully will have some more answers soon enough to help these patients. Until then, we have many more questions than we do answers.

Internal Medicine rater

A negative meta-analysis is sometimes useful for discussion! During the turbulent Covid-19 times, the temptation to adopt very quickly 'seducing' therapies without any evidence in favor is great ... we have seen this a lot! It is obvious that all the published studies on convalescent plasma are of very low methodological quality level ... no surprise that the meta-analysis is unable to conclude (Garbage in, garbage out!); this exercise will be useful once we have the published results of RCT! In the meantime, the merit of this meta-analysis is to point to the absence of evidence!

Public Health rater

This review conducted was too early to be informative. Most studies are ongoing...