COVID-19 vaccines offer robust protection against SARS-CoV-2 infection in people with cancer, according to an article published online June 5 in Cancer Cell. Vaccine protection levels are generally better for people with solid cancers than for patients with cancers of the blood, the researchers report, although most people with any cancer made detectable antibodies to the coronavirus after receiving a vaccine. Patients receiving treatments that suppressed the activity of their immune system, such as B cell–depleting therapies for leukemia, produced fewer antibodies after receiving a vaccine than did recipients with solid cancer.

Earlier this year, oncologists reported that COVID-19 is deadlier for people with blood cancer than it is for people with solid tumors. This was before vaccine uptake was widespread in the United States. The authors of the current study suggest that almost all people with cancer would benefit from vaccination, perhaps coupled with additional strategies to stimulate antibody production.

“The overall message is overwhelmingly positive,” says coauthor Amit Verma, who heads the blood cancer division at the Montefiore Medical Center in New York City. “Vaccines are good and they do work, even in cancer patients.”

People with blood cancers such as some forms of lymphoma or leukemia produce an unsustainable level of B cells if left unchecked and therefore often undergo B cell–depleting therapies. The trouble, Verma notes, is that COVID-19 antibody production depends on those very same B cells. Someone receiving a B cell depleting therapy who takes a COVID-19 vaccine may need to take additional measures to boost antibody production, he explains.

In this study, 200 cancer patients at the Montefiore Medical Center completed a full COVID-19 vaccination series—either with the two-dose Moderna or Pfizer/BioNTech vaccines, or the single-dose Johnson & Johnson vaccine. Among them, 134 patients had a solid tumor, while 66 patients had blood cancer of some kind. The researchers compared antibody production levels in these two groups, based on the results of a standard antibody test.

Almost all of the solid tumor patients (98 percent) produced antibodies to the SARS-CoV-2 spike protein in sufficient abundance to be detected by the antibody test, as did a large majority (85 percent) of people with blood cancer. The volunteers with solid tumors had significantly higher antibody levels compared with those diagnosed with blood cancer and made just as many antibodies as 26 people without cancer who served as a control group. The participants with blood cancer made fewer antibodies than those without cancer.

Among the cohort with blood cancer, patients on B cell–depleting therapies were less likely to make detectable antibodies than were blood cancer patients taking other types of treatment. For instance, 73 percent of patients who received a stem cell transplant, which wipes out B cells, made detectable antibodies, as did 70 percent of patients on a treatment known as anti-CD20 therapy, which does the same. None of the three patients who received CAR T cell therapy, which also reduces B cells, made detectable antibodies.

Twenty-two cancer patients in this study had already contracted and recovered from COVID-19 by the time they received a vaccine, and all but one of these individuals made detectable antibodies, generally at significantly higher levels than did the cancer patients who had not contacted COVID-19.

Boosting antibody production

The exact antibody levels needed to provide robust protection against COVID-19 remains unknown, although researchers in the United Kingdom reported yesterday their estimates for the levels of  antibodies needed to prevent symptomatic COVID-19.

“We do know there’s some relationship between the production of neutralizing antibodies and the ability to protect [against COVID-19 infection]. We just don’t know where the line is,” says E. John Wherry, the director of the Institute for Immunology at the University of Pennsylvania’s Perelman School of Medicine. Wherry, who was not involved in the study Verma was part of, notes that this lack of clarity about antibody levels needed is true for many vaccines, not just those for COVID-19.

Verma’s study “is, I think, confirming initial reports that patients with hematologic malignancies don’t have as much success mounting antibodies as patients with solid cancer or patients without cancer at all. They should continue to invoke precautions of social distancing and wearing masks, even when vaccinated,” says Mikkael Sekeres, the chief of hematology at the University of Miami’s Sylvester Cancer Center who did not participate in this study. He says that such precautions are particularly important as the contagious Delta variant of COVID-19 becomes more prominent.

A clinical strategy that physicians could consider for some patients, Verma notes, would be to time the administration of vaccines in advance of the delivery of B cell–depleting therapies. Perhaps giving a COVID-19 vaccine first and then waiting several days to administer the cancer drug would enable some antibody production to the virus. Verma says he thinks this would work better for newly diagnosed blood cancer patients who are not yet receiving any treatment, rather than for patients for whom these B cell–depleting therapies are an essential part of their care.

“If you take away these therapies, the B cells come back, but the cancer comes back too,” Verma cautions.

In addition to timing vaccination and therapy schedules for certain patients, other strategies for boosting antibody production could be to offer a vaccine booster shot or monoclonal antibodies to some patients. Verma says that all of these options are on the table, and that clinical trials are necessary to resolve which strategies will work best in different situations.