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Real-world protection from COVID-19 vaccination is better than expected in transplant recipients, reducing the risk of symptomatic infection by almost 80% in those who have had both doses compared with unvaccinated controls, a new transplant registry analysis shows.
“Persons who have received an organ transplant are considered to be at increased risk for COVID-19 and for a severe outcome because their immune systems are necessarily suppressed to ensure their transplants are successful and lasting,” lead author Saima Aslam, MD, professor of medicine, University of California San Diego School of Medicine, said in a statement from UCSD.
Because numerous studies have demonstrated reduced antibody responses to SARS-CoV-2 in solid organ transplant recipients and variable effect on T-cell responses, there has been a need to study clinical effectiveness and breakthrough infections in those who are vaccinated, they explain.
“These findings offer strong evidence that getting vaccinated provides significant protection,” Aslam noted.
The investigators say that recent data from France, as well as other studies, show an increased rate of detectable antibodies following a third dose of the Pfizer-BioNTech COVID-19 vaccine in organ transplant recipients, “but based on our data it is unclear if a third dose is clinically warranted.”
But they stress that almost half of the solid organ transplant recipients analyzed in the study had not been vaccinated at all, even by the beginning of 2021 when the US was well into a third wave of COVID-19 infections.
So there is still a significant need, the authors say, to continue to improve outreach efforts to those in the transplant community and promote the benefits of being fully vaccinated.
The study was published online recently in Transplant Infectious Disease.
The researchers analyzed clinical data from the UC San Diego transplant registry from January 1 through June 2 of this year, with 2151 solid organ transplant recipients identified. The patients had received a variety of solid organ transplants including kidney, liver, lung, and heart, the largest percentage having received a donor kidney.
Among all patients, 912 were fully vaccinated and 1239 were not (1151 of those 1239 received no vaccine at all and 88 had been partially vaccinated; these 1239 served as the control group).
Fully vaccinated patients had received two shots of either the Pfizer-BioNTech COVID-19 or the Moderna vaccine, or a single dose of the Johnson and Johnson vaccine. The majority, at nearly 70%, had received the Moderna vaccine. The mean age of the cohort was 57 years and the median time since patients had undergone transplantation was almost 5 years (57.5 months).
During the 6-month study interval, 65 cases of COVID-19 were documented in the group overall. Only 4 cases occurred among fully vaccinated individuals whereas 61 cases occurred among the unvaccinated, including in 2 patients who had been partially vaccinated.
Among the 4 cases that occurred among the fully vaccinated, 2 were considered mild and were treated on an outpatient basis, and the other 2 were moderate, requiring hospitalization and treatment with remdesivir.
There were no COVID-19-related deaths among the 4 patients who experienced breakthrough infections whereas 2 (3.3%) of 61 of control patients died of COVID-19-related causes.
The authors note that the incidence rate for COVID-19 was 0.065 per 1000-person days among the fully vaccinated compared with an incidence rate of 0.34 per 1000-person days in the control group.
Booster Doses for Especially Vulnerable Transplant Recipients?
“These findings are encouraging for a couple of reasons,” said co-author Kristin Mekeel, MD, chief of transplant and hepatobiliary surgery at UCSD.
“First, they demonstrate real-world clinical effectiveness of COVID-19 vaccination in a vulnerable population,” she notes.
“Second, the effectiveness is better than expected,” she added, “given that studies have found that only about half of solid organ transplant recipients develop detectable antibodies after vaccination.”
Although calls for patients who are immunosuppressed to receive a third booster dose of a COVID-19 vaccine may not be necessary, “prioritizing at-risk subsets of transplant recipients based on immunological profiles and clinical characteristics for a third vaccine dose could be considered,” they say, adding it’s still vitally important for transplant patients to continue to mask and practice social distancing.
And it is especially important for transplant recipients to encourage household members to get vaccinated too, especially given the current COVID-19 surge in San Diego.
The study was funded by the Cystic Fibrosis Foundation.
Aslam reports receiving grants from the Cystic fibrosis Foundation as well as honoraria from Gilead and Merck. Study author Susan J. Little, MD, received grant funding from Gilead Sciences. Mekeel has disclosed no relevant financial relationships.
Transpl Infect Dis. Published online July 29, 2021. Full text