The evolution of the SARS-CoV-2 virus has presented ongoing challenges in the prevention and treatment of COVID-19, particularly since omicron and its subvariants began to emerge. 

Vaccine development has not kept pace with the emergence of new variants, and monoclonal antibodies (mAbs) that were previously used for COVID-19 prevention and treatment are ineffective against the omicron subvariants currently in circulation.

These developments are especially concerning for patients who are moderately to severely immunocompromised and thus at higher risk for more severe and lasting symptoms, hospitalization, and death due to COVID-19.1

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Many cancer patients are included in that group, noted Julie Gralow, MD, chief medical officer and executive vice president of the American Society of Clinical Oncology (ASCO).

“Patients with hematologic malignancies, those with solid tumors on active cytotoxic chemotherapy or certain immunosuppressive or immunomodulatory biologic agents, those who have undergone stem cell or bone marrow transplant — and may remain on immunosuppressive drugs — and those on high doses of corticosteroids meet the CDC’s definition of moderately to severely immunocompromised,” Dr Gralow explained. 

Methods of preventing and treating COVID-19 in these vulnerable patients have had to evolve alongside the SARS-CoV-2 virus. 

Vaccine Efficacy May Vary, Vaccination Still Recommended

Even before the original omicron variant (BA.1) emerged, studies suggested that cancer patients did not always mount an adequate response to COVID-19 vaccination, and the risk of breakthrough COVID-19 and death was higher in cancer patients than in the general population.2-6 

Breakthrough COVID-19 was found to be even more common in cancer patients after omicron emerged, and recent research suggests cancer patients still have a higher risk of breakthrough COVID-19, hospitalization, and death than the general population.7,8

Some recent studies in the general population have suggested that the bivalent mRNA vaccines can provide better protection against omicron subvariants than monovalent mRNA vaccines.9-11 Other studies have suggested that bivalent vaccines may be no more effective than monovalent vaccines against the currently circulating omicron subvariants.12-15  

Data showing the effects of the bivalent vaccines in cancer patients are limited. One small study suggested that Pfizer-BioNTech’s bivalent vaccine increased virus-neutralizing capacity against the BQ.1.1 subvariant but not against the XBB.1 and XBB.1.5 subvariants.16 

Although the antibody response to vaccination may be suboptimal in immunocompromised patients, the “vaccines have the advantage of stimulating multiple arms of the immune system, which likely still offers some degree of protection, even with omicron subvariants,” according to Amy Sherman, MD, instructor at Harvard Medical School, associate physician at Brigham and Women’s Hospital, and clinician-scientist with the Precision Vaccines Program at Boston Children’s Hospital in Massachusetts. 

Patients should be encouraged to get a bivalent booster in addition to the initial monovalent vaccine series, said Sarah Hochman, MD, assistant professor at NYU Grossman School of Medicine and section chief of infectious diseases at Tisch Hospital in New York, New York. 

“As new variants arise, new vaccines likely will be made to better match these variants, and staying up to date with these new boosters will be important,” Dr Hochman said. 

Staying up to date on vaccinations is particularly important for hematopoietic stem cell transplant recipients, noted Eric Tam, MD, a blood and marrow transplant and hematology-oncology specialist at the USC Norris Comprehensive Cancer Center at Keck Medicine in Los Angeles, California.

“Post-hematopoietic stem cell transplant patients need to be revaccinated, usually after 3 months post-transplant,” he said.