First Estonian COVID-19 patient received convalescent plasma therapy

In early summer, nearly 500 people wanted to take part in the study by researchers of the University of Tartu and donate their blood plasma so that it could be used to treat people suffering from COVID-19. Eleven of them made it to the donor chair and donated 20 plasma doses in total. Now, the first severely ill corona patient has received the plasma transfusion with antibodies to SARS-CoV-2.

At the peak of the first wave of the corona pandemic, medical researchers of the University of Tartu, doctors of Tartu University Hospital and the Blood Centre of the North Estonia Medical Centre invited 18–56-year-olds who had recovered from COVID-19 to donate blood plasma to use it for treating severely ill patients.

One of the leaders of the study, Associate Professor in Anaesthesiology and Intensive Care at the University of Tartu Juri Karjagin said that as the ways to cure COVID-19 are limited, doctors and medical researchers decided to try an age-old method: transfusion of blood plasma of people recovered from the infection (convalescent plasma). “In the prevention and treatment of infectious diseases, convalescent plasma transfusions have been used for more than one hundred years. Newer examples include the swine flu outbreak and SARS-1 pandemic,” said Karjagin.

Donor profile

The researchers’ and doctors’ call to donate blood plasma brought nearly 500 people to sign up by email or phone. “First, doctor Ain Kaare communicated with the potential donors to determine the initial suitability for the study. Many were interested in becoming donors, but very few of them met all the eligibility criteria,” said Karjagin. So only 36 women and 19 men passed the initial selection.

Based on these 55 people, we can say that the average donor candidate was 37 years old, weighed 73 kg and had a haemoglobin level of 139. Most of them had type 0 or type A blood – 16 and 26 people, respectively. Less than half of donor candidates had had a cough as their symptom, but also sore throat and difficulty breathing were reported. The most frequent symptoms were fever and taste change. 48 people had suffered from a mild form of the disease and recovered at home, three were hospitalised in a general ward and two in intensive care.

Confirmation of donors’ eligibility

In the selected 55 donor candidates, the number of antibodies was determined and also a neutralisation test was carried out to assess the efficiency of antibodies. “As we were not sure whether the antibodies alone manage to suppress the virus, we carried out a neutralisation test in cooperation with the Veterinary and Food Board and laboratories of the University of Tartu,” explained Karjagin.

For that, the SARS-CoV-2 isolated in Estonia was mixed with plasma and incubated for one hour. Then the Vero E6 cells were added and the mixture was incubated at 37°C for four to seven days. The result of the test was evaluated by microscope.

“With the test, we determined the titres, which were too low in 35 of 55 donors, meaning that their antiviral activity would not have achieved the goal. This left us with 20 patients. Nine of them proved not suitable for a variety of other reasons: a recent tattoo, diagnosed Lyme disease or the donor’s reaction to the venous procedure,” described Karjagin. So 11 people reached the apheresis procedure for donating blood plasma. In total, 20 plasma doses were collected.

First patient received plasma therapy

So far, the convalescent blood plasma had been waiting for its time in a freezer, but last week, the first opportunity of plasma transfusion opened up, as Tartu University Hospital had admitted a patient with a severe form of COVID-19 who met all the eligibility criteria.

“There are many criteria the patient must meet to receive convalescent plasma,” said Karjagin. For instance, the person must have fallen ill less than ten days ago. “Within that period, the patient’s own level of antibodies is sufficiently low. If we can administer existing antibodies to the patient at that time, it may alleviate the progress of the disease,“ Karjagin explained. There is no point in doing the procedure for a patient in intensive care, as the patient’s own antibodies have developed by that time.

Other prerequisites include acute dyspnoea, a respiratory rate above 25 breaths per minute and the chest X-ray showing infiltrates in more than 50% of the lung field.

Karjagin was hopeful that soon, a positive treatment outcome can be observed in the first Estonian patient to have received convalescent plasma.