Some medications are expected to present a slight setback, but aren’t necessarily disastrous for COVID-19 immunization, because they suppress just a sliver of the immune system’s typical operations. One example is ustekinumab (Stelara), a common treatment for Crohn’s disease, which zaps the signals that immune cells send one another—an intervention akin to temporarily putting a military’s radio system on the fritz. Many of these treatments can continue on schedule during vaccination, under the advisement of a physician.
Other drugs, however, are far blunter tools, clobbering large swaths of the immune system. Among them is Rick Phillips’ drug, rituximab (Rituxin), which is used to treat rheumatoid arthritis, multiple sclerosis, lupus, and white-blood-cell cancers such as leukemia and lymphoma. It destroys entire populations of B cells—on par with blitzing a fleet of naval forces. B cells are antibody factories, and without them the immune system has more difficulty committing new viruses to memory. “We’ve pharmacologically made a hole in the immune system,” Erin Longbrake, a neurologist at Yale New Haven Hospital who is studying COVID-19 vaccine responses in multiple-sclerosis patients, told me. After a rituximab infusion, B cells can take six months or more to bounce back.
The lasting impacts of B-cell-depleting therapies have prompted many physicians to recommend that such drugs be administered with careful timing around a COVID-19 shot. “It’s the medication I worry about the most,” Anna Helena Jonsson, a rheumatologist at Brigham and Women’s Hospital, in Boston, told me. Rick Phillips was three months out from his most recent infusion of rituximab when he received his first dose of Pfizer’s vaccine, in February. He pushed back his next infusion until mid-April—a month later than usual—in hopes of giving his COVID-19 shots’ protective powers time to take hold.
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People who have an autoimmune disease that’s poorly controlled, though, could risk a symptom flare by delaying their medications; others who have received organ transplants, or who are at the beginning or middle of a chemotherapy course, can’t simply flip their medications off. Some people will need to prioritize their existing treatment, “then just get the vaccine when you can,” Chaitra Ujjani, an oncologist at the Seattle Cancer Care Alliance who is studying COVID-19 vaccine responses in people with blood cancers, told me.
People living with HIV are facing a different type of immune deficit. The virus annihilates immune cells called helper T cells, which coax young B cells into churning out antibodies and spur other T cells, called killers, to assassinate infected cells. Without helper T cells, the body’s coordinated defenses against disease very often crumble. “We know from other vaccines that people with very low [helper T-cell] counts do not mount a good response,” Boghuma Kabisen Titanji, an infectious-disease physician who works with HIV patients at Emory University, told me. Potent antiretroviral therapies can buoy helper T-cell counts, but they don’t work for everyone. Titanji’s strategy with her patients has been to manage expectations about vaccination: “You will get some protection, but I can’t tell you for certain you’ll have the same degree of protection as others.”