Organ Transplant Recipients May Not Mount Strong Response to COVID Vaccine

People who are immunosuppressed, including those who have undergone a solid organ transplant, could be at risk for COVID-19 even after vaccination, according to a study conducted by researchers at Johns Hopkins University.

Researchers studied immune responses to the first dose of the Moderna and Pfizer-BioNTech vaccines in solid organ transplant recipients, who are often immunosuppressed.

Recipients need to take immunosuppressant drugs after their transplant to prevent the organ from being rejected. The medication regimen dulls the body’s immune response to help ensure that the new organ is accepted, but can also render patients more susceptible to infection by SARS-CoV-2 and other pathogens.

“These data help us understand the biology of the first vaccine dose of a two-dose series,” lead study author Brian Boyarsky, MD, a resident at the Johns Hopkins University School of Medicine, tells Verywell. In addition, Boyarsky says that they provide insight into a neglected clinical population, as “transplant recipients were excluded from the original mRNA vaccine trials.” The March study was published in JAMA.

Reduced Antibody Response

The study included 436 solid organ transplant recipients who had received the first dose of either the Moderna vaccine (mRNA-1273) or the Pfizer-BioNTech vaccine (BNT162b) between December 16 and February 5.

The researchers evaluated immune response by testing the recipients’ blood samples for antibodies to one of two different domains—or regions—of the SARS-CoV-2, the virus that causes COVID-19, spike protein.

Through the testing, the researchers hoped to pinpoint the people who had mounted an immune response to the shot.

It turned out only 17% of the study population had detectable antibodies within 20 days of vaccination. Younger people and people who received the Moderna vaccine were more likely to respond than older people and people who received the Pfizer-BioNTech vaccine.

“This is in stark contrast to people with healthy immune systems who are vaccinated, nearly all of whom mount a sufficient antibody defense against COVID-19,” Boyarsky said in a press release.

Three Factors Influence Antibody Production

The researchers found that adherence to a particular class of immunosuppressants influenced how likely the vaccine dose was to provoke an immune response in the recipients.

“Certain types of immunosuppressants, called anti-metabolites, which are commonly taken by transplant recipients, were associated with poorer antibody generation after the first dose of the vaccine,” Boyarsky says. “We expect these medications to decrease antibody production, so we were not totally surprised by poor antibody generation following mRNA vaccination. What surprised us was the magnitude of the poor antibody response.”

Several other factors, including a recipient’s age and the vaccine brand, also impacted the immune response. Specifically, being younger and receiving the Moderna vaccine were associated with heightened antibody production.

Boyarsky says that the results make clinical sense. “Young people, in general, have more robust immune systems—this was demonstrated in the original mRNA vaccine trials,” Boyarsky says.

The participants who received the Moderna vaccine were twice as likely as those who received the Pfizer-BioNTech vaccine to have an immune response.

Should You Try to Get the Moderna Vaccine Instead of Pfizer’s?

At this point, Boyarsky would not necessarily recommend the Moderna vaccine over the Pfizer-BioNTech vaccine for organ transplant recipients. “The different vaccines have different doses of mRNA, so it is possible that may contribute to the differences in antibody generation,” Boyarsky says.

Emily Blumberg, MD, director of the transplant infectious diseases program at Penn Medicine in Pennsylvania, tells Verywell that antibody production following vaccination is only one metric of immunity. “Importantly, this study is only looking at one part of the immune response—it doesn’t examine either the full immune response or whether the vaccine prevents people from getting more critically ill, so there is still a lot to learn,” she says.

The preliminary results of the study suggest that organ transplant recipients could still develop symptoms of COVID-19 weeks or longer after getting vaccinated.

“At this point, based on the evidence we have, we agree with the general recommendations that transplant recipients would benefit from whatever vaccine is available to them at the time,” Boyarsky says. “Furthermore, we believe that transplant recipients’ family members and social networks should also be vaccinated.”

What About Johnson & Johnson?

Since the publication of the study, Boyarsky and his colleagues have begun to examine the impact of non-mRNA vaccines, such as Johnson & Johnson’s, on immunity in solid organ transplant recipients. 

They hope to use the data to develop a medical solution for “folks who don’t have robust vaccine responses,” Boyarsky says. For now, it remains imperative to take basic public safety precautions. Don’t let the Band-Aid on your arm lull you into a false sense of security.

“No vaccine is ever foolproof—remember, even in the original studies in non-immunosuppressed patients, the vaccines worked incredibly well, but there were still rare cases of COVID that can occur,” Blumberg says. “For now, until more people are vaccinated and we learn more about the specific transplant patient vaccine response, it is important to continue to mask, socially distance, avoid crowds, and wash your hands.”

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