While one in four blood cancer patients do not produce detectable antibodies after their first two doses of the COVID-19 vaccine, 43% of them will produce antibodies after a third dose, according to new data from The Leukemia & Lymphoma Society (LLS). For some patients with blood cancer, the third dose led to antibody levels seen in healthy adults. This was confirmed by measuring levels of detectable antibodies to the spike protein in SARS-CoV-2 before and after the third dose of the mRNA COVID-19 vaccines. Results from the study, the largest of its kind to date, also demonstrate that blood cancer patients who had at least some antibodies after the first two doses are likely to produce large amounts after the third vaccination.
“Our data shows a clear benefit of giving blood cancer patients three primary vaccine doses, but there is still a large portion of patients who will remain at risk even with the additional dose,” says Lee Greenberger, Ph.D., LLS chief scientific officer. In this study, about 20% (139/699) of blood cancer patients still had no measurable COVID-19 antibodies after the third dose. The results, which were reported Saturday at the American Society of Hematology (ASH) Annual Meeting in Atlanta, are from the largest pool of blood cancer patients reported to date.
Vaccines stimulate production of anti-spike antibodies, which can block entry of the COVID-19 virus into human cells. Having these antibodies appears to offer protection from getting sick or having severe disease. However, for many blood cancer patients, their antibody levels may not be as strong as those in fully vaccinated, healthy adults – making them more susceptible to a COVID-19 breakthrough infection.
The data reported by LLS are from the LLS National Patient Registry, which has been tracking COVID-19 vaccine response among more than 11,000 blood cancer patients since February 2021. LLS previously reported findings from first and second dose vaccination, as well as a smaller study with third vaccination in near real-time, to help blood cancer patients and their oncologists make informed decisions about vaccines and other measures they can take to avoid infection.
The larger pool of data in the current study, from 699 patients, provides more robust information about how the third COVID-19 mRNA dose works in patients with all types of blood cancer. The study does not include information about response to Johnson & Johnson vaccines.
The study was weighted to include more patients with blood cancers that deplete the immune system’s B-cells, which are responsible for making antibodies. Patients with these types of cancer, including chronic lymphocytic leukemia, diffuse large B-cell lymphomas, follicular lymphomas, marginal zone lymphomas, mantle cell lymphomas, and Waldenstrom’s Macroglobulinemia, are less likely to develop antibodies. In patients that failed to make antibodies to the initial vaccination, the antibody response after the third vaccination ranged from 0%-48%.