COVID-19 vaccines, like all vaccines, protect people by firing up their immune system to recognize and obliterate the virus.
But what happens when a person’s immune system is dampened by illness or medication?
A recent study of transplant recipients, who take drugs to suppress their immune system, found that most failed to produce antibodies against the coronavirus after a first dose of vaccine.
“It’s very important for transplant recipients to know that they are not necessarily immune” to COVID-19 after vaccination, said Dr. Dorry Segev, an author of the study, published in the Journal of the American Medical Association.
Recent guidelines from the US Centers for Disease Control and Prevention say that fully vaccinated people can safely gather indoors with other vaccinated people and with unvaccinated members of one household. But that advice may not apply to people with weakened immune systems, who should maintain the same masking and distancing protocols even after getting the shot, said Segev, a transplant surgeon and director of the Epidemiology Research Group in Organ Transplantation at the Johns Hopkins University School of Medicine.
People who have received organ transplants must take immunosuppressants to prevent their bodies from rejecting the organ. In the recent study, Segev’s team measured the antibody levels of 436 transplant recipients who received one dose of either the Moderna or the Pfizer vaccines. Only 76 participants — 17 percent — had detectable antibodies to the coronavirus about three weeks after receiving the first dose.
But many questions remain unanswered. It’s possible that transplant recipients will mount a stronger immune response after more time has passed. The second dose — which none of the study participants had received — might be enough to kick the antibodies into action. Possibly, other vaccines using different technologies will prove more effective in transplant recipients.
Also, the study didn’t measure whether the vaccines activated other parts of the immune system that could provide protection even in the absence of antibodies. The study had other limitations: It did not enroll a representative sample of transplant recipients and had no control group.
“We have to be careful reading anything into these early findings other than a very clear warning to immunosuppressed transplant patients that they may not have immunity,” Segev said.
But Segev said it’s still important for transplant recipients to get vaccinated, to take advantage of whatever protection they can get.
Dr. Camille Nelson Kotton, clinical director for Transplant and Immunocompromised Host Infectious Diseases at Massachusetts General Hospital, said she wasn’t surprised by the findings. Typically, immunocompromised people don’t get the same level of protection from vaccines as people with robust immune systems. But she was “somewhat disappointed.”
“I was hoping there would be a better response,” Kotton said. Because the Moderna and Pfizer vaccines use a novel technology, she’d hoped they might work for transplant patients better than other vaccines. “I was cautiously optimistic that somehow we’d get lucky this time,” she said.
Instead, she’s cautioning her patients, who have been calling her about Segev’s study, that they should not assume that the vaccine is keeping them safe. At the same time, she urges them to get vaccinated.
“Any level of protection may well be better than no protection,” she said.
Many of her patients have been asking for antibody tests, but Kotton does not recommend them. Such tests provide no useful information because no one knows what level of antibodies is needed to protect against the coronavirus.
There are about a half-million transplant recipients in the United States, Segev said, a tiny sliver of the population. But some 11 million people take immune-suppressing drugs, usually to treat autoimmune conditions such as lupus or rheumatoid arthritis, and they, too, need to be cautious, he said. In a separate, small study published Tuesday, the Johns Hopkins team found only 30 percent to 60 percent of people with certain autoimmune disorders who took immune-suppressing drugs developed an antibody response after receiving Pfizer or Moderna vaccines.
As for people whose immune systems are weak for other reasons, such as HIV infection, there’s no evidence yet on how well the vaccine will work. “It may be that anybody with a compromised immune system in some way or another may have a more sluggish response,” Segev said.
Immunocompromised people were excluded from clinical trials of the COVID-19 vaccines, noted Dr. Dan H. Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center. So he welcomed Segev’s study. “These are important data,” he said.
Barouch, who worked on developing the Johnson & Johnson COVID-19 vaccine, saw nothing surprising in the study.
“It is expected that vaccines will have reduced immune response in immune-suppressed populations,” he said. But despite this, he added, it’s especially important for these populations to get vaccinated. “Even a lower level of protection is still worthwhile,” he said.
Dr. Robert Finberg, who led the Pfizer vaccine trial at the University of Massachusetts Medical School, said the situation is far from hopeless for transplant recipients.
“I think it’s likely the second dose will help,” Finberg said. And the other COVID-19 vaccines, which work through different biological mechanisms, may turn out to be more effective for immune-compromised people.