A large-scale study by Vilnius University (VU) suggests coronavirus vaccines are less effective for blood cancer patients, some of whom developed no immunity to Covid-19.
The study, conducted at VU Santara Clinics and led by Laimonas Griškevičius, traced immune reactions of some 900 blood cancer patients after they were give the Pfizer-BioNtech vaccine.
“Our main finding is that reactions to the vaccine varied widely among these patients,” Griškevičius tells LRT.lt. “We presumed that blood cancer patients may not have as strong an immune response to the vaccine as healthy people. It's what our study confirmed.”
According to Griškevičius, 20 percent of the study subjects did not develop any immunity to Covid-19 after receiving two vaccine shots, while 40 percent had lower antibody count compared to the control group. The remaining 40 percent developed sufficient immunity to the coronavirus.
Another co-author of the study, Tomas Beinortas of Cambridge University Hospital, says that response to vaccination depends on the treatment patients receive during immunisation. Active chemotherapy can render vaccination ineffective.
“One can claim that patients who have not been receiving any active treatment for at least six months do develop immunity after the Covid-19 vaccination. The longer the period since the treatment, the stronger the immunity,” Beinortas tells LRT.lt. “Meanwhile, those who get vaccinated during therapy do not essentially develop any immunity to Covid-19.”
Younger blood cancer patients also respond better to immunisation.
Beinortas says nine patients in the study came down with Covid-19 within three months of getting two vaccine shots, six of them developed severe symptoms and needed oxygen therapy. Three of them passed away.
“Our study is the first in the world to show that, for this group of patients, full vaccination does not necessarily give protective immunity. The patients who died had very low antibody counts,” Beinortas says.
The findings, according to the study authors, has serious implications for efforts to protect blood cancer patients, who are among the most vulnerable groups to Covid-19.
Most of them receive outpatient treatment and come to hospital only for chemotherapy. “These patients go to work, to shops, they walk among us and lead ordinary lives. If they do not develop sufficient immunity after vaccination, they are in great danger of getting Covid-19,” says Griškevičius.
In some cases, if a patient's condition permits, it might be advisable to postpone active treatment for a few weeks or months until they are vaccinated and develop immunity to Covid-19.
Moreover, evidence suggests that giving the third vaccine shot could boost blood cancer patients' antibody count.
“Small-sample studies with non-blood patients who had weaker immunity suggest that, once they were given the third dose, some of them had stronger immunity,” Griškevičius says.
However, Lithuania's authorities have yet to decide whether to authorise booster shots for vulnerable groups.
The study will be continued, Griškevičius adds. “The purpose is to monitor immune responses every three months.”
“If third vaccine shots are authorised, our continuing study will be able to tell us whether it is indeed useful,” says Griškevičius. “The international medical community and blood cancer patients are looking forward to this data.”