London: The weakened immune
systems of blood cancer patients can improve after they receive a third
Covid-19 vaccination, finds a new study.
Patients with lymphoma have
defects in their immune system that restrict their response to vaccination.
Despite this, the new study found improvements in antibody and T-cell responses
after a third vaccine dose, except in patients who had recently received a
certain antibody treatment for their cancer.
"Despite the gradual
lifting of Covid-19 restrictions worldwide, a cloud continues to hang over
immunosuppressed patients, who may not develop protective immune responses
after vaccination," said Sean Lim from the University of Southampton, who
led the research.
"In particular,
individuals with haematological malignancies are at greater risk of severe
Covid-19 disease even if they have been vaccinated," Lim added.
For the study, published in
the journal Nature Cancer, the team collected blood samples from 457 adult
lymphoma patients before they received their first vaccination of either the
Oxford-AstraZeneca or BioNTech Pfizer vaccines, and four weeks after the first
dose, two to four weeks and six months after the second dose, and four to eight
weeks after the third dose.
The study aimed to evaluate
the strength of the immune system's response to the vaccines and to help
predict how effective the vaccine could be for lymphoma patients.
To achieve this, the
scientists measured the ability of antibodies in the blood samples to prevent
the viral spike protein from binding to ACE2 proteins, which are the virus's
key point of entry into the human body.
They also measured the
response of T cells, which form part of the body's immune system, when
stimulated by the viral spike.
The results showed that whilst
just over half of patients undergoing active cancer treatment had no detectable
antibody levels after the second vaccination, T cell responses could be detected
in about two-thirds of all patients.
After a third dose, 92 per cent of patients who were not undergoing anti-CD20 treatment for their cancer showed improved antibody responses, compared to 17 per cent who were receiving that treatment.
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