According to a German study by Rotterdam et al presented at the 2021 American Society of Hematology (ASH) Annual Meeting & Exposition (Abstract 218), about 15% of people with blood cancers and other blood disorders had no vaccination-related antibodies after receiving a COVID-19 vaccine. Although researchers say it is encouraging that 85% of study participants did show an antibody response, the findings suggest that additional precautions may be warranted to prevent COVID-19 infection among people with blood disorders.

The study examined antibody levels after COVID-19 vaccination in people with blood cancers such as lymphoid and myeloid neoplasms, autoimmune disorders, and noncancerous disorders of blood or immune cells. The results suggest that patients with lymphoma and those currently receiving treatment are the least likely to build antibodies in response to a COVID-19 vaccine.

“Some patients with hematologic diseases do not have an adequate antibody response and might, therefore, not have sufficient protection from vaccination,” said senior study author Susanne Saussele, MD, of III. Medizinische Klinik, Medizinische Fakultät Mannheim, Universität Heidelberg, Germany. “This study can help guide vaccination strategies for these patients. In addition, our study suggests that when it is possible to delay beginning treatment for their underlying disorder, it may be best to wait so that a patient can receive a vaccine or booster first.”

People with blood disorders face a high risk of hospitalization and death if they become infected with COVID-19, especially if they are older or have received therapies that reduce B-cells. Since the majority of participants in the study did respond to COVID-19 vaccines, the results underscore the role of vaccination as an important strategy for preventing severe disease, researchers said. However, the findings also suggest vaccination should be complemented with other precautions. “We should recommend ongoing protective measures such as masks, social distancing, and screenings, as well as prioritizing vaccination for family members and caregivers to protect the patients,” Dr. Saussele said.

Study Details and Findings

For the study, the researchers recruited 373 patients treated for blood disorders at University Hospital Mannheim in Germany and measured vaccine-related antibodies in their blood a median of 12 weeks after final vaccination. More than 90% of participants had blood cancer, while 9% had either autoimmune disease or a nonmalignant blood disorder. Most patients had received the Pfizer/BioNTech vaccine; 10% received the Moderna vaccine, 7% received the AstraZeneca vaccine, and 6% received one dose from each of the two vaccine types.

Overall, 85% of participants tested positive for vaccine-related antibodies and 15% tested negative. The rate of negative antibody results was highest among those with lymphoid neoplasms, a group of diseases that include lymphoma, myeloma, and lymphoid leukemia. Among these patients, 36% tested negative for vaccine-related antibodies. Patients with indolent non-Hodgkin lymphoma had the weakest response to vaccination overall.

Being on active therapy was associated with a reduced antibody response. Overall, 61% of study participants were on active therapy. Of those who tested negative for vaccine-related antibodies, most—71%—were on active therapy. Therapies correlated with a negative response were rituximab, ibrutinib/acalabrutinib, and ruxolitinib.

“Our study suggests that most people with blood malignancies—not only those who are currently under treatment—should monitor their antibody levels and work closely with their care team to determine how to continue to protect themselves from COVID-19,” Dr. Saussele said. “Antibody measurements offer a hint of who has responded to the vaccine and can perhaps ease up on precautions a bit.”

Dr. Saussele noted that the results are limited in that the study did not examine participants’ T-cell response to vaccination, meaning that some patients’ level of protection may have been underestimated.

The researchers plan to continue to measure antibody levels for at least a year and to assess participants’ rates of breakthrough infections and response to vaccine boosters.

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