Jun 12

Convalescent Plasma Therapy for treating COVID-19

Written by Tabinda Salman | posted in General Awareness | 1 Comment

As Covid-19 continues to cause havoc worldwide, scientists are working to create antidotes to the current coronavirus, which began infecting humans late last year. Scientists and researchers are pursuing various strategies for developing therapeutic therapies that can counter the novel coronavirus. Convalescent plasma therapy is one such treatment that is in sight right now.

In Pakistan many clinical trials were conducted for convalescent plasma treatment. In the past the treatment was used experimentally and thus became a ray of hope to fight the novel coronavirus pandemic. This therapy is still under consideration as a standard treatment for coronavirus and is used only for study and trial purposes because it lacks adequate scientific evidence to support its efficacy thus it is only used as a preventive measure and not a treatment for the Covid-19 disease according to researchers.

The Plasma therapy has been used selectively so far, mostly in severe cases where patients were on ventilator support.

To know what actually plasma therapy is, let’s find out details below:

Convalescent plasma therapy

The treatment of any infection has three ways to manage:

  • The first is to develop active immunity means to vaccinate the person. The antibodies develop and it helps in fighting infection.
  •  Secondly, to give some medicines that can kill the virus.
  • The third is to give antibodies or immunoglobulins from outside.

This third option is the base of plasma therapy. The plasma of a cured patient has abundance of antibodies and when they are transfused in patient, they can lower the activity of virus. This is known as the passive immunity.

What is convalescent plasma?

People who have recovered from COVID-19 have antibodies to the disease in their blood. These antibodies are called convalescent plasma. So, overall the recovered COVID-19 patient’s blood develops antibodies to battle against COVID-19.  If you have fully recovered from COVID-19, you may be able to help patients currently fighting the infection by donating your plasma. Once the blood of the first patient is infused to the second patient, those antibodies will start fighting against coronavirus in the second person.

Procedure of plasma therapy

Plasma therapy is a process where the blood of the recovered patient is taken, and the donated blood is then tested for any other disease-causing agents such as hepatitis B, hepatitis C, HIV etc. Later, plasma (the liquid portion of the blood containing antibodies) is separated from the blood and is given to the infected covid patients (just as blood transfusion). The plasma is taken only from those recovered persons whose body contain high amount of antibodies and who agree to donate blood. Upon extraction, the antibody-rich plasma is then absorbed into a patient’s body under treatment. These antibodies of the recovered patient begins to attack and battle the novel coronavirus in the second patient once it has been absorbed into anyone under care and it helps the patient to fight efficiently against covid antigen. The process explained is simply the Convalescent plasma therapy and is also called as passive immunisation. This treatment can also be used to immunise people at high risk of contracting the virus such as health personnel, patient relatives, and other partners at high risk.

Protocol of plasma therapy transfusion

In an ideal situation, when a person has caught Covid-19 infection and recovered, he should be asked if he would like to donate his plasma in case it is needed for serious patients. Once his consent is obtained he is kept on the list of potential donors. About 28 days later he is called to donate Plasma ideally, this should be done by a process called Apheresis where only the Plasma is extracted and the blood cells are returned to the patient.

This has two advantages:

  • The patient does not feel the weakness/ fatigue which can sometimes happen after a whole blood transfusion
  • Since only Plasma is removed the person is potentially able to donate again in a short span of two weeks or so.

This Antibody rich Convalescent Plasma is then stored at an appropriate temperature like blood in a blood bank. In case of any emergency situation, treating team decides the use of this plasma as a therapeutic option for the infected ICU patient. They have to do some matching and compatibility testing before starting this 250 ml plasma infusion intravenous to the existing patient.  

How does plasma therapy works

When a person gets infection due to any virus, the immune system of body makes antigen to that virus. This antigen binds to virus to identify it as target by WBC and other cells. Once the antibody identifies the pathogen or virus it is easier for WBC to target and kill them. Like, identifying the real enemy like corona virus the antigen or antibody’s role is very vital. When the plasma enters blood stream of receiving patients it immediately starts identifying viruses and start flagging the target. Once the flagging is done WBC starts targeting the virus. Meanwhile the host body immune system also learns the technique and another line of defence becomes ready. One cured person’s plasma can produce two doses of the transfusion material. Critically ill patients receive 200-400ml of plasma intravenously, and their progress is then carefully monitored.

History of convalescent plasma therapy

This is not the first time when a convalescent plasma therapy is perceived as a viral infection treatment. The idea dates back over a century that is in 1890 when a German physiologist Emil von Behring discovered that it was effective in avoiding the infection caused by diphtheria when he took the serum from an infected rabbit. In the past, during many outbreaks, the same forms of treatment are used, including the Spanish flu pandemic of 1918, the diphtheria epidemic of 1920. The plasma therapy was used as a treatment during the H1N1 infection of 2009. In 2014, the World Health Organisation (WHO) had recommended the use of convalescent plasma therapy to treat patients with the antibody-rich plasma of those who had recovered from the Ebola virus disease. For the treatment of people infected with Middle East Respiratory Syndrome (MERS) in 2015, a protocol for use of convalescent plasma was established.

Trials and studies so far

Trials and researches are going for COVID-19 treatment but no permanent solution is out yet. It is still an experimental procedure for COVID-19 patients.

  • A research in China found the therapy as effective in treating COVID-19 patients on small sample size. In the study, a trial was performed in which a dose of 200 ml of convalescent plasma was given to 10 adult COVID-19 patients with serious symptoms. The patients showed considerable progress, and the virus vanished in seven patients without any substantial adverse side effects. The sick get only temporary passive immunisation in this therapy. It lasts mainly less than a week and remains in the bloodstream until the time the injected antibodies stay.
  • In Houston, the same trial was conducted and it is said that three critical ill COVID-19 patients are also showing signs of recovery from the convalescent plasma therapy.

Limitations of plasma therapy

Here we should know that plasma therapy also have some limitation. Few are discussed below:

  • Plasma treatment is done only under severe conditions, because till now, blood donors are also scarce who have successfully recovered from COVID-19.
  • Plasma treatment is still not a confirmed cure for everyone, as this doesn’t work for everyone.
  • While vaccination provides life-long immunity, in the case of passive immunisation or plasma therapy, the effect lasts only so long as the injected antibodies remain in the blood.
  • We need confirmed cured willing donors
  • According to some researchers and doctors, if not performed properly, plasma therapy could lead to life-threatening complications.
  • Extensive testing of blood sample of donor is required.
  • Availability of plasma separation devices and skilled people are required to do that.
  • The treatment carries risks, such as the transfusion  can transmit blood-borne pathogens, and in rare cases lead to conditions such as transfusion-related acute lung injury (TRALI), in which transferred antibodies damage pulmonary blood vessels, or transfusion-associated circulatory overload (TACO), when the patient’s body doesn’t adapt to the added blood volume, which can be up to half a litre.
  • Antibody Titres should be done to judge for the effectiveness of the Plasma, otherwise it’s not effective.
  • According to the researchers, investigation is still necessary to determine if convalescent plasma might shorten the duration of illness reduce morbidity or prevent death associated with COVID-19.

Many countries around the world like China, India, Pakistan, Turkey, South Korea, Italy, the United Kingdom, have begun using plasma to treat patients infected with coronavirus and the treatment has shown some favourable results in improving patient health. Currently, there is no cure for the virus but there are many ongoing vaccine trials. On behalf of NAYS- Pakistan, we would like to encourage Coronavirus survivors to come forward and donate their blood in order to save their fellow countrymen.

Help Pakistan against fighting COVID-19 please:


Article: Ms. Sundeela Fayyaz

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  1. Sarosh Saleem

    Good overview of plasma therapy.
    It has been duly mentioned that regular testing of donors is also required.
    It has been mentioned in the beginning that this treatment is still under trial and yet at the end it is advised as a treatment n people are requested to donate. It’s encouraging to see that it is being trialed in Pakistan too but do the donors n recipients know that they are part of a trial?
    A few things remain however, when does a person develops enough antibodies to donate? Also, is the donated plasma being tested for other markers like cytokines etc?
    Bottom line is that it’s a good thing that it is being trialed n tested as a mode of treatment in Pakistan but that’s about it…we have to wait until the results are so convincing that it is established as a treatment option. Until then, it’s just a hope with an equal probability of turning out to be a false one!

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