In one of the largest studies to date of the antibody response to vaccination against COVID-19 in people who had been treated for acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), patients responded well to two doses of the Moderna mRNA vaccine and saw a pronounced increase in levels of antibodies against the virus after receiving their second vaccine dose. The study findings were presented by Jain et al at the 2021 American Society of Hematology (ASH) Annual Meeting & Exposition (Abstract 217).

“We observed a strong antibody response to the vaccine in a group of patients at high risk for severe COVID-19, including among patients who were on active treatment for AML or MDS,” said senior study author Jeffrey E. Lancet, MD, of the H. Lee Moffitt Cancer Center and Research Institute. “The fact that antibody levels increased so dramatically after the second vaccine dose suggests potential utility in additional dosing, even for patients who initially respond poorly to the vaccine.”

Jeffrey E. Lancet, MD

Previous studies had shown that patients with other types of blood cancer—specifically, B-cell lymphomas or chronic lymphocytic leukemia—often have a poor antibody response to vaccination with one of the COVID-19 mRNA vaccines. Treatment of these cancers suppresses the ability of the immune system to produce white blood cells such as B cells and T cells to fight off infection.

“The treatment of myeloid cancers such as AML and MDS, including allogeneic transplantation, also suppresses white blood cells and leaves patients vulnerable to infection,” explained Dr. Lancet. “We conducted this study to find out whether patients with these cancers would also have a suppressed or absent immune response to COVID-19 vaccination.”

Study Population Details

The study involved 46 patients who either had previously or were currently undergoing treatment for AML or MDS. The patients’ median age was 68 years; 59% were male, and 96% were White. On average, they were about 2 years out from the diagnosis of their cancer.

Fifteen patients (33%) were receiving treatment for their cancer at the time they were vaccinated. Thirty-two patients (70%) had undergone a transplant of blood-forming stem cells from a healthy donor as part of their cancer treatment. Forty patients (87%) were in remission when they were vaccinated. The investigators noted that some patients are counted twice—eg, if they had undergone a stem cell transplant and were in remission, they would be counted in both categories. (For this reason, the percentages add up to more than 100%.)

All patients received a first dose of the Moderna mRNA vaccine in late January 2021 and a second dose 4 weeks later. The investigators collected blood specimens from each patient before each vaccine dose was administered and again at 4 weeks after the second dose. The primary aims of the study were to describe the immune response and assess the safety profile of the vaccine in a cohort of patients with AML or MDS.

Results

Blood test results at 29 days after the first vaccine dose showed that 70% of patients had an antibody response; at 57 days—following the second dose—97% had an antibody response. Antibody levels were significantly higher after the second dose compared with after the first dose.

Patients’ antibody response was not significantly affected by age, sex, race, disease status (ie, active or in remission), time from disease diagnosis to vaccination, number of treatments patients had undergone for their cancer, whether patients had received a stem cell transplant, or whether they were on active treatment at the time of vaccination.

The most common adverse events following vaccination were the typical ones reported after vaccination with a COVID-19 mRNA vaccine, such as fatigue, headache, arm swelling, and mild pain at the injection site.

“The study results should be confirmed in a larger group of patients,” Dr. Lancet said. “However, based on these data, we feel comfortable advising patients with AML or MDS that they should get vaccinated against COVID-19. Due to their vulnerability to COVID-19, they stand to benefit from the vaccine more than most.”

This is an observational study without an identified control group, Dr. Lancet cautioned. Another limitation is that because the participants were overwhelmingly White, it is not known whether patients of other races or ethnicities would show a similar antibody response. In addition, the actual protective effect of the vaccine and the T-cell responses to it in this patient population are not yet known; the researchers are currently gathering these data.

The investigators are now following the same cohort of patients to determine whether a third dose of the vaccine can achieve even higher antibody levels than were seen after the second dose.

Disclosure: For full disclosures of the study authors, visit ash.confex.com.