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.

Additional Protective Measures, Emerging Challenges

Patients should “continue to follow nonpharmacological behavioral preventative measures, including avoiding crowds, masking in public, social distancing, and hand hygiene,” advised Sherif Mossad, MD, an infectious disease specialist at Cleveland Clinic and associate professor in the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University in Ohio. 

Dr Mossad also noted the importance of at-home testing using COVID-19 rapid antigen detection tests. Patients should self-test if they develop COVID-19 symptoms, and a positive test should prompt contact with their health care provider. Symptomatic patients who test negative should pursue PCR testing. 

Close contacts of cancer patients should follow these measures as well and stay up to date with vaccinations to create a “circle of protection” around patients, Dr Mossad said. 

With the newer variants, the “virus binds more strongly to our cells and has mutations that allow it to escape the immune response,” said Jim Boonyaratanakornkit, MD, PhD, an infectious disease specialist and researcher at the Fred Hutchinson Cancer Center in Seattle, Washington. The greater transmissibility of these variants underscores the importance of preventive measures, he added.  

“While we don’t have a single ‘magic bullet’ for prevention and protection for our patients, the combination of vaccination, masking, and testing is the best way to optimize protection using all the tools available,” Dr Sherman said.  

Unfortunately, these tools are becoming more difficult for cancer patients and the general public to use as the pandemic wears on. Though anecdotal reports suggest cancer patients tend to wear masks and would like others to wear masks around them, mask mandates are largely a thing of the past, even in some health care settings.17-19 

Another potential barrier to protecting patients from COVID-19 is the impending end of the public health emergency, which will take place on May 11.20 Although COVID-19 vaccines will remain available and Moderna’s vaccines will remain free, Pfizer is planning to charge for its COVID-19 vaccines.21

The end of the public health emergency also means that patients with Medicare will no longer receive free at-home COVID-19 tests.22 Some patients with private insurance may have access to free at-home tests, but others may not. Likewise, COVID-19 tests ordered or given by health care professionals may or may not be free after the public health emergency ends.

One method of COVID-19 prevention that was found to be effective for cancer patients but is no longer an option is tixagevimab-cilgavimab (Evusheld).23-25 The US Food and Drug Administration (FDA) recently withdrew the emergency use authorization (EUA) for Evusheld when it was shown to be ineffective against more than 90% of the omicron subvariants circulating in the United States at the time. 

Changes to COVID-19 Treatment, Remaining Options 

Like the case with Evusheld, many mAbs that were previously authorized for COVID-19 treatment are no longer authorized for use because they are not active against currently circulating variants, Dr Hochman said. 

Over the course of the pandemic, the FDA has revoked EUAs for several mAbs once used to treat COVID-19, including bamlanivimab-etesevimab, casirivimab-imdevimab (REGEN-COV), bamlanivimab alone, sotrovimab, and bebtelovimab.26-31 

However, there are a few antiviral therapies that are expected to remain active against the dominant subvariants of SARS-CoV-2 when administered early in the course of illness. These include nirmatrelvir-ritonavir (Paxlovid), remdesivir, and molnupiravir.32 

“Paxlovid is the preferred treatment for most outpatients, or remdesivir if Paxlovid is contraindicated, and the oral antiviral molnupiravir is authorized as an alternative when Paxlovid and remdesivir are not accessible or clinically appropriate,” Dr Tam said.33  

Due to the potential for severe drug-drug interactions with Paxlovid, particularly with certain immunosuppressant medications, close monitoring and dose adjustments may be needed when initiating Paxlovid, Dr Tam noted.

“I always confer with a pharmacist first to ensure that Paxlovid won’t have any drug-drug interactions with the medications my patients are already on,” said Rahul Banerjee, MD, an assistant professor in medical oncology at the University of Washington and the Fred Hutchinson Cancer Center in Seattle.

Dr Hochman explained that while molnupiravir does not carry the risk of drug-drug interactions associated with Paxlovid, it does “pose a theoretical risk of being incorporated into host DNA, leading to mutations,” and thus is contraindicated for use in pregnant patients or for “men of reproductive potential who are sexually active with women of childbearing potential for the duration of treatment and for 3 months after completing treatment, unless they use a reliable method of contraception.”34 

Dr Mossad also noted that clinicians should be aware of the risk for rebound symptoms in patients treated with Paxlovid or molnupiravir.35,36 

For patients who are hospitalized for COVID-19 but don’t require oxygen, remdesivir is recommended.37 For hospitalized patients who require conventional oxygen, options include remdesivir plus dexamethasone, baricitinib, and tocilizumab. Baricitinib and tocilizumab can be combined with dexamethasone in patients who require high-flow nasal cannula oxygen, noninvasive ventilation, mechanical ventilation, or extracorporeal membrane oxygenation.

COVID-19 convalescent plasma, in the outpatient or inpatient setting, is an additional option for patients who have immunosuppressive disease or are receiving immunosuppressive treatment.38 

For pediatric cancer patients, treatment strategies are limited, said Diego Hijano, MD, assistant faculty member in the department of infectious diseases at St. Jude Children’s Research Hospital in Memphis, Tennessee. 

Paxlovid can be used to treat mild to moderate COVID-19 in nonhospitalized patients who are 12 years or older, weigh at least 40 kg, and are at high risk of progression to severe COVID-19.39

However, for children under 12 years of age who are high risk and have mild-to-moderate COVID-19 symptoms, remdesivir is the only available treatment that can be used to prevent severe disease, Dr Hijano said. 

For children who already have severe COVID-19, remdesivir, dexamethasone, baracitinib, tofacitinib, and tocalizumab are options.40 

“For patients who have moderate to severe disease requiring hospitalization and supplemental oxygen, we use remdesivir and dexamethasone,” Dr Hijano noted. “For patients who can’t receive steroids or have a lack of response in the first 24 hours, we consider the use of baricitinib.” 

Unmet Needs: Better Vaccines, Treatments, and Guidelines 

There are still many areas of need in COVID-19 prevention and treatment, according to experts. 

“The biggest needs are in vaccine research, drug development, and education targeting vaccine hesitancy,” Dr Hochman said. Researchers should aim to “develop vaccines that target areas other than the SARS-CoV-2 spike protein, which has mutated over time and resulted in reduced protection from prior SARS-CoV-2 infection,” she added.

Dr Banerjee pointed to the need to develop mAbs like Evusheld that could protect against new variants and to create a faster pipeline to get these mAbs to vulnerable patients. 

“Many of our patients aren’t able to mount adequate responses to COVID-19 vaccines because of their underlying malignancies or the treatments they’re on, so the ability to confer passive immunity is critical,” he said.

Dr Hijano hopes to see changes in the regulatory process to allow the identification of a prophylactic mAb for younger children. 

“The fast pace at which SARS-CoV-2 changes has left children under 12 years to almost never have a monoclonal option available, because every time companies were opening trials in children, the monoclonals were ineffective against the newest variants and the study could not continue,” he explained. He also noted the need for antivirals that can be used in all age groups. 

Another unmet need is COVID-19 management guidelines relevant to specific patient groups.

“Most of the current guidelines are for immunocompromised patients in general, which lumps together people with hematologic malignancies, solid organ transplantation, and those receiving immunomodulatory therapy for inflammatory or rheumatologic conditions,” Dr Sherman said. “We urgently need more specific guidelines for each of these groups of patients, since the underlying disease and treatments received impact the immune system differently.” 

“Clinicians need to be able to provide evidence-based recommendations to protect all patients with cancer and be able to address the vast amount of misinformation propagated on social media and through other avenues,” Dr Gralow said. “That means staying up to date and understanding the evidence and rationale for recommendations.”

Disclosures: Dr Mossad, Dr Gralow, Dr Hochman, Dr Tam, and Dr Hijano reported having no relevant disclosures. Dr Banerjee disclosed relationships with SparkCures, Sanofi Pasteur, Genentech/Roche, Janssen Oncology, Bristol-Myers Squibb/Celgene, and Pack Health. Dr Sherman is involved in COVID-19, HIV, and other vaccine trials conducted in collaboration with the National Institutes of Health, HIV Vaccine Trials Network, COVID Vaccine Prevention Network. Dr Boonyaratanakornkit disclosed research funding from Vir Biotechnology and GlaxoSmithKline.


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This article originally appeared on Cancer Therapy Advisor