Johns Hopkins Medicine researchers report that a prospective study of 14 infants and children demonstrated that convalescent plasma — a blood product collected from patients recovered from infections with the coronavirus (SARS-CoV-2) that causes COVID-19 — was safe in high risk children infected with or exposed to the virus.
“Even once a SARS-CoV-2 vaccine is available for all ages, there are going to be some immunocompromised children who won’t be able to mount a robust enough immune response from the vaccine, so it’s incredibly important that we study all possible therapies to treat them,” says the study’s lead author Oren Gordon, a pediatric infectious disease fellow at Johns Hopkins Children’s Center.
The researchers have now teamed up with a network of children’s hospitals across the country to continue studying the use of convalescent plasma for high risk children. They hope to gather more safety data and collect information on how centers are choosing which children should be offered the plasma.
Convalescent plasma has been used throughout the COVID-19 pandemic to provide naturally generated antibodies against the virus for high risk people. A recent Johns Hopkins Medicine clinical trial of more than 1,000 high risk adults, for example, found that the use of plasma early in the course of infection can decrease the risk of hospitalization for adults by 54%. However, data on children has been harder to come by, the researchers noted.
In the new study, carried out between May 2020 and April 2021, 14 children age 3 months to 17 years were given convalescent plasma within four days of exposure to the coronavirus, or within five days of the onset of COVID-19 symptoms. Six of the children were hospitalized, and the other eight remained outpatients. The children — treated at Johns Hopkins Children’s Center — were all considered high risk, with factors including chronic lung disease, cerebral palsy, liver failure and cancer, making them more likely to develop severe COVID-19 symptoms. The researchers collected blood samples from the children over the two months following their transfusions to study how their bodies metabolized the plasma.
On average, 30 minutes after administration of plasma, the levels of antibodies in the blood of recipients were 6.2% of the antibody concentration seen in donors. This antibody level was expected due to dilution of the donor plasma by the recipients’ blood during transfusion. Studies of adults have suggested that amount of antibody — while much lower than in the plasma donors — is enough to protect recipients from severe COVID-19.
The researchers also saw antibody levels steadily decline over 14 to 21 days following plasma transfusion. This, while also expected, they say, means the children treated with convalescent plasma did not receive lasting protection from the treatment. The quick decline also means that selecting donor plasma with the highest possible antibody levels is critical to ensuring that levels in recipient children start off at a high enough level.
Because the study results also suggest that the plasma is metabolized in children much the way it has been reported to metabolize in adults, the Johns Hopkins team believes convalescent plasma’s effectiveness in children is likely similar as well.