Study finds that the vaccine is much less effective in leukemia patients, but the research is helping determine the best time to vaccinate.
By Yakir Benzion, United With Israel
A study by researchers at Tel Aviv’s Sourasky Medical Center and released over the weekend has revealed that coronavirus vaccines are much less effective than expected for people being treated for leukemia, but the data collected is helping to determine the optimum time to vaccinate.
It is known that patients with chronic lymphocytic leukemia (CLL) have an increased risk for severe COVID-19 disease and mortality The study sought to determine the effectiveness of the COVID-19 vaccine when given to these patients.
Because the vaccine clinical trials did not include patients with blood cancers, who are at high risk of severe illness and complications from the coronavirus, gauging the effectiveness of the vaccine in this population is critically important.
Doctors gave 167 Israeli patients the Pfizer vaccine, known technically as the BNT162b2 mRNA COVID-19 vaccine, and compared them to a control group. They found that the vaccine had a marked drop in effectiveness depending on what type of cancer therapy the patients were receiving and how advanced their treatment was.
“Overall, the response rate to the vaccine was significantly less than what we see in the general population, which is most likely attributed to the presence of cancer itself and certain CLL treatments,” said Dr. Yair Herishanu, associate professor in hematology and head of the CLL service at the Tel Aviv Sourasky Medical Center, who headed the study.
“It would seem that if you are untreated, in what we call ‘watch and wait,’ or do not have active disease, you can gain more benefit from the vaccine,” Herishanu said. “Patients who responded the best were in remission, which makes sense because their immune system had a chance to recover.”
The report concluded that unfortunately, “antibody-mediated response to BNT162b2 mRNA COVID-19 vaccine in patients with CLL is markedly impaired and affected by disease activity and treatment.”
However, together with a similar study by the National and Kapodistrian University of Athens, the researchers believe their work will give doctors more solid information in order to determine the ideal time to give coronavirus vaccinations to people with CLL.
“Even though response rates were not optimal, patients with CLL should still get the vaccine and, if appropriate, it may be better to do so before CLL treatment starts, although the disease itself may affect the response,” said Dr. Herishanu. “Equally important is continuing to take precautions – wearing a mask, avoiding crowds, keeping a social distance, and being sure close contacts get vaccinated against COVID-19.”
Herishanu and his team will continue to follow these patients for 12 months to see how many, if any, develop COVID-19 infection following vaccination. Since this study only assessed antibody response, they also plan to check the cellular immune response to gain a more complete picture of the extent to which patients are protected after vaccination.
The researchers noted that the same trends would be expected with the mRNA vaccine made by Moderna.