Coronavirus antibodies in donated blood plasma fade quickly after symptoms first appear, a new study suggests.
The researchers tracked a small group of recovered COVID-19 patients who donated their blood and found that they all showed decreases in antibodies after three months.
Only three weeks later the values for half of the detectable antibodies fell again.
The team at Héma-Québec, a blood donation center in Québec, Canada, says the results suggest that the sooner plasma is collected after someone has recovered from COVID-19, the better.
Additionally, they add that studies of antibody tests to see how many people have recovered from the virus may be below the true number.
Convalescent plasma therapy is when the liquid portion of the blood is taken from a recovered COVID-19 patient and transferred to sick patients in the hope that they will develop the antibodies needed to fight off the infection. Pictured: a medical worker holding a bag of blood plasma
A new study from Héma-Québec, Canada found that 15 recovered COVID-19 patients who donated plasma saw antibody levels decline after three months and again 21 days later. Pictured: a woman who donates plssma
Convalescent plasma therapy is when the liquid portion of the blood is withdrawn from a liquid coronavirus patient.
The hope is that the antibodies and immunity in the blood of a healthy person will be transferred to a sick person.
From this, the infected person then develops the antibodies that are required to fight the coronavirus.
The treatment was first used during the 1918 Spanish flu pandemic, a situation not far from the coronavirus pandemic.
In August, the US Food and Drug Administration (FDA) approved the treatment for emergency approval last week. President Donald Trump hailed the decision as "really historic".
However, a panel of the National Institutes of Health released a statement stating that there isn't enough data to show that plasma therapy is effective at improving survival rates.
The study author Dr. Renée Bazin of Héma-Québec says this study is among the first to show recovered COVID-19 patients can switch from seropositive to seronegative.
This means that patients test positive for antibodies against the coronavirus and at a certain point no longer have any detectable antibodies.
"While many clinical studies are ongoing to better understand whether convalescent plasma is clinically beneficial for the treatment of COVID-19, a key question is when it is most effective to collect donor plasma based on the presence of antibodies that will help fight the virus. " & # 39; She said.
"As far as we know, antibodies against the new coronavirus are not forever."
For the study, published in the journal Blood, the team examined data from 15 plasma donors in Quebec.
All adults were diagnosed with COVID-19 and subsequently recovered from the infection.
While they were sick, their symptoms ranged from mild to severe, but none of them were sick enough to be hospitalized.
Participants donated their plasma between four and nine times. The first donation was made 33 to 77 days after the onset of symptoms and the last donation 66 to 114 days after the symptoms appeared.
All 15 donors showed a decrease in antibodies after 88 days. About 21 days later, half of the detectable antibodies decreased again.
The team says the number of donations had nothing to do with it and was simply a naturally dwindling immune response.
"Antibodies are disappearing quickly, so people who are recovering from COVID-19 and looking to donate blood plasma shouldn't wait too long to be eligible to donate," said Dr. Bazin.
"Ideally, based on our findings, clinicians should use plasma collected early after a donor's symptoms appear and test for the presence of antibodies before giving donor plasma to a patient."
The results also have implications for studies that use antibody test results to find out how widespread the virus is in a community.
"If antibodies decline three to four months after a peak of infection, we can underestimate the prevalence of infection in communities or populations," said Dr. Bazin.
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