Organ transplant recipients 'should not assume immunity' from COVID-19 vaccine
Only 54% of solid organ transplant recipients demonstrate evidence of antibody development after receiving the COVID-19 vaccine, according to data in a pair of research letters published in JAMA.
“This study was important because transplant recipients and other immunocompromised people were excluded from the original vaccine trials,” Brian J. Boyarsky, MD, of the Johns Hopkins University School of Medicine, in Baltimore, told Healio Rheumatology. “We did not know how well these highly immunogenic vaccines would work in transplant recipients.”
To analyze the immunogenicity of mRNA vaccines among the immunocompromised, Boyarsky and colleagues conducted a pair of studies examining first, the quantified humoral response to the first dose of the COVID-19 vaccine, and subsequently, the antibody response after the second dose, among solid organ transplant recipients.
First Dose: Just 17% demonstrate antibody response
The first study included 436 transplant recipients, recruited from across the United States through social media, who received the COVID-19 vaccine between Dec. 16, 2020, and Feb. 5. None had previously tested positive for COVID-19.
Blood samples were collected either at home by the patient, using the TAPII blood collection device, or via standard venipuncture. TAPII samples were assessed using the EUROIMMUN anti–SARS-CoV-2 S enzyme immunoassay, which tests for antibodies to the S1 domain of the SARS-CoV-2 spike protein. Meanwhile, the venipuncture samples were tested using the Roche Elecsys anti–SARS-CoV-2 S enzyme immunoassay, which is designed to find antibodies against the receptor-binding domain of the SARS-CoV-2 spike protein.
Among the participants, the median age was 55.9 years, 61% were women and 89% were white. Fifty-two percent received the Pfizer-BioNTech vaccine, while the remaining 48% were inoculated with the Moderna vaccine. The median time since transplant procedure was 6.2 years, and the most common regimens for maintaining immunosuppression included tacrolimus, in 83%; corticosteroids, in 54%; and mycophenolate, 66%. Other regimens included azathioprine, in 9%; sirolimus, in 4%; and everolimus, in 2%.
According to the researchers, by a median of 20 days following the first dose, 17% of the included transplant recipients had demonstrated a detectable antibody response (95% CI, 14% to 21%). In addition, participants who were receiving anti-metabolite maintenance immunosuppression therapy were less likely to develop an antibody response than those not receiving such immunosuppression therapy — 37% compared with 63%, respectively (adjusted IRR = 0.22; 95% CI, 0.15-0.34). Older participants were also less likely to have an antibody response, with an adjusted IRR of 0.83 (95% CI, 0.73-0.93) per 10 years.
Patients who received the Moderna vaccine were more than twice as likely to develop an antibody response that those who received the Pfizer formulation — 69% compared with 31%, respectively (adjusted incidence rate ratio = 2.15; 95% CI, 1.29-3.57). According to the researchers, his findings was largely backed up in a sensitivity analysis, limited to 245 participants who were tested 14 to 21 days following vaccination (adjusted IRR = 2.29; 95% CI, 1.32-3.94).
Second Dose: Improved response but risks remain
The second study included 658 transplant recipients, all without prior confirmed COVID-19, who completed their two-dose vaccine series between Dec. 16, 2020, and March 13. All participants were followed through April 13. As with the first study, the researchers used semiquantitative anti-spike serologic testing with the Roche Elecsys anti–SARS-CoV-2 S enzyme immunoassay, using a positive cutoff of at least 0.8 U/mL, or the EUROIMMUN enzyme immunoassay, with a positive cutoff of at least 1.1 arbitrary units.
According to the researchers, at a median of 29 days following the second dose, 54% of participants registered a detectable antibody response (95% CI, 50% to 58%). Overall, 15% demonstrated measurable antibody response after both dose one and two, while 46% had no antibody response after either dose. Approximately 39% had no antibody response after dose one, but later demonstrated antibody response after dose two.
Median antibody levels among all participants following the second dose were 2.14 U/mL, for the Roche test, and 1.23 arbitrary units, for the EUROIMMUN immunoassay. Among the participants with an antibody response after dose two, median antibody levels were 142.1 U/mL and 6.48 arbitrary units, compared with 34.7 U/mL and 5.05 arbitrary units among those with no antibody response after dose one, and greater than 250 U/mL and 9.23 arbitrary units in those who registered a response after the first dose.
Among the 473 participants who were taking antimetabolites, 8% demonstrated an antibody response after doses one and two, and 57% had no antibody response after either dose, while 35% had an antibody response only after the second dose. Among the 185 participants who were not receiving antimetabolites, 32% had an antibody response after both doses, 18% had no response after either dose, 50% demonstrated a response only after the second dose.
Bottom Line: ‘Transplant recipients should not assume immunity’
“The big takeaway is that vaccinated transplant recipients should not assume immunity after vaccination,” Boyarsky said. “Even among those who had seroconverted, their antibody levels were relatively lower than what we see in people with competent immune systems.”
Despite these findings, Boyarsky said he still encourages transplant recipients to receive the COVID-19 vaccine. He also stressed the importance of inoculation among people who are close to those who are immunocompromised.
“The antibody response to vaccination is one part of the greater immune response to vaccination,” Boyarsky said. “In spite of relatively low antibody responses, we encourage transplant recipients to be vaccinated. It is also particularly important family members, friends and social networks of the immunocompromised get vaccinated to confer some level of protection to the most vulnerable.”