BENGALURU: Although there is still uncertainty about the clinical benefits and role of convalescent plasma to treat Covid-19, new research suggests that the earlier plasma is harvested after recovery, the better. Antibodies start to disappear after three months of the onset of symptoms, states a release based on a study by the American Society of Hematology.
"A key question is, at what point is it most effective to collect donor plasma, based on the presence of antibodies that help fight the virus. Based on our findings, antibodies against the new coronavirus are not eternal," said Renée Bazin, PhD, of the Héma-Québec Blood Center (Canada) and author of the study published in the journal, Blood.
This small study, which drew from 282 plasma donors in Quebec, Canada, followed 15 adults (11 males and 4 females) who were diagnosed with and subsequently recovered from Covid-19.
Participants donated their plasma between four and nine times each, with the first donation between 33 and 77 days after the onset of symptoms, and the last donation between 66 and 114 days.
All 15 donors showed a decrease in antibodies at the same time -- around 88 days -- and half of the detectable antibodies decreased within 21 days afterward.
"The antibodies disappear rapidly, so people recovering from Covid-19 who want to donate blood plasma should not wait too long once they become eligible to donate," Bazin said.
She noted that nearly 7% of the original 282 donors did not have detectable antibodies at their first donation, and this proportion doubled when donors waited 11 to 12 weeks after symptom onset.
Dr U S Vishal Rao, Associate Dean, Centre for Academics and Research, HCG Cancer Hospital, said the study stands right.
"We have observed that in most recovered patients, antibodies start to decline after three months. The best time to donate plasma is one month from the infection to within three months. We studied data of more than 350 patients and found not everyone has high antibody titers post recovery."
At HCG, plasma donors are put through a Vitros test, wherein if the value of antibody titre is 12 and above, it means the plasma is effective.
Dr Ranjit Mohan, consultant, Infectious Medicine, Manipal Hospitals, said the study's results are true for any infection -- as time goes by, antibodies reduce as they are no longer required by the body, but do not completely disappear.
For Covid, it is important that plasma is harvested at the appropriate time, he added.
"We must permit time to allow antibodies to rise to optimal levels, before they start reducing. This time window where antibody levels are good is between four-eight weeks post recovery. We also have to make sure the person has completely recovered, finished two weeks of quarantine post discharge, is in good health and has good antibody levels," Dr Mohan said.