Despite being fully vaccinated, transplant recipients remain at greater risk for COVID-19
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After a second dose of either the Moderna or Pfizer-BioNTech COVID-19 vaccine, solid organ transplant recipients failed to achieve an antibody response against SARS-CoV-2 comparable to the general population.
According to a related press release, this study continues research that the team from Johns Hopkins School of Medicine conducted earlier in 2021, which showed 17% of transplant recipients “produced sufficient antibodies” after one dose of the two-dose regimen.
“While there was an increase in those with detectable antibodies — 54% overall — after the second shot, the number of transplant recipients in our second study whose antibody levels reached high enough levels to ward off a SARS-CoV-2 infection was still well below what’s typically seen in people with healthy immune systems,” Brian J. Boyarsky, MD, PhD, said in the release. “Based on our findings, we recommend that transplant recipients and other immunocompromised patients continue to practice strict COVID-19 safety precautions, even after vaccination.”
For the study, Boyarsky and colleagues included 658 transplant recipients who completed a two-dose vaccine regimen between December 2020 and March 2021.
Researchers found the first dose led to a detectable antibody response in 15% of transplant recipients; the response occurred at a median of 21 days after the first dose was administered. After the second dose, an antibody response was detectable in 54% of participants, occurring a median of 29 days later (46% had no response after either dose).
“Although no threshold has been established for protective immunity, antibody levels were well below that which has been observed in immunocompetent vaccinees,” the researchers wrote, noting that median antibody levels after the second dose were 2.14 U/mL for all participants (including those with no response) and were 142.1 U/mL for those who had detectable antibody levels after the second dose.
Participants who received the Moderna vaccine were more likely to develop an antibody response than were those who received the vaccine from Pfizer-BioNTech, results suggested.
Co-investigator on the study Dorry Segev, MD, PhD, also commented on the findings in the release, advising: “Given these observations, transplant recipients should not assume that two vaccine doses guarantee sufficient immunity against SARS-CoV-2 any more than it did after just one dose.”
Perspective
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Yihung (Eric) Huang, MD
As organ transplant recipients were excluded from the original clinical trials on SARS-CoV-2 vaccines, the post-vaccination report from Johns Hopkins and similar results from Israel fill an important knowledge gap.
Not surprisingly, the humoral response from SARS-CoV-2 vaccines is lower in kidney transplant recipients compared with healthy controls. Even in those with detectable response, the level of anti-spike antibody is lower than in the control group. Reduced response in transplant recipients has also been observed with other vaccines. For example, seroconversion rate after receiving regular-dose influenza vaccine is only about half of that achieved in the general population.
However, even in those without measurable antibody, vaccination may not have been in vain. Although humoral response is easier to measure, it does not represent the entirety of immune response. There is limited evidence that some kidney transplant recipients do develop SARS-CoV-2 specific T-cells after vaccination despite lack of antibody.
Given these uncertainties, I would not recommend routine monitoring of SARS-CoV-2 antibody after vaccination in kidney transplant recipients despite the commercial availability of the test. A positive test might offer a false sense of security, and we do not currently have proven mitigation for a negative result.
Analogous to the use of high-dose influenza vaccine to improve seroconversion in transplant recipients, booster shots or higher doses of SARS-CoV-2 vaccines may eventually need to be considered in this population. However, this strategy would need to be better studied before it can be implemented widely.
For now, I would advise kidney transplant recipients to maintain precaution and vigilance even after full vaccination. Mask wearing has been part of the arsenal to protect immunocompromised patients even before the current pandemic, and it is not time to put away those masks yet. One minor silver lining of the pandemic may be that mask wearing is now less stigmatized than before. It is also important for all eligible household members to get vaccinated to help protect the vulnerable. Finally, we should strongly urge all patients with chronic kidney disease awaiting transplants to get vaccinated. Although humoral response to SARS-CoV-2 vaccines in patients on dialysis is also lower compared with health controls, it is still way better than in their transplanted counterpart.
References:
Boyarsky BJ, et al. JAMA. 2021;doi:10.1001/jama.2021.7489.
Chavarot N, et al. Transplantation. 2021;doi:10.1097/TP.0000000000003784.
Grupper A, et al. CJASN .2021;doi:10.2215/CJN.03500321.
Grupper A, et al. AJT. 2021;doi:10.1111/ajt.16615.
Natori Y, et al. Clin Infect Dis. 2018;doi:10.1093/cid/cix1082.
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