Vaccinated organ transplant recipients may remain at high risk for COVID-19 - study

While all participants in the control group displayed a positive antibody response to spike protein, only 51 of the 136 (37.5%) organ transplant recipients had positive serology.

By ZACHARY KEYSER
Israelis are seen along the light rail tracks on Jaffa Street in Jerusalem amid the coronavirus pandemic, on February 3, 2021. (photo credit: MARC ISRAEL SELLEM/THE JERUSALEM POST)
Israelis are seen along the light rail tracks on Jaffa Street in Jerusalem amid the coronavirus pandemic, on February 3, 2021.
(photo credit: MARC ISRAEL SELLEM/THE JERUSALEM POST)
Researchers have found that organ transplant recipients may remain at high risk for COVID-19 even after being fully vaccinated against the novel coronavirus.
The Israeli study analyzed the humoral responses of 139 kidney transplant recipients after receiving both shots of the Pfizer-BioNTech vaccine, benchmarking their results against a control group of 25 healthy participants.
While all participants in the control group displayed a positive antibody response to spike protein, only 51 of the 136 (37.5%) organ transplant recipients had positive serology.
Across the board, the mean antibody levels "were significantly lower" in comparison to the control participants, the researchers said. Transplant recipients who did in fact display a positive serology were typically younger than those without.
Additionally, the longer period of time between transplantation and vaccination was "significantly associated" with positive serological response to mRNA vaccines.
"The most significant predictors of failure to mount a humoral response in our cohort of kidney transplant recipients were advanced age, need for high dose corticosteroids during the last (pre-vaccination) year, maintenance with three immunosuppressive medications, and a regimen that includes [Mycophenolate mofetil] MMF," the study authors wrote.
Researchers added that MMF is known to have a "suppressive effect on the immune system, including inhibition of antibody production," noting that "the greater the degree of immunosuppression, the less likely the patient will respond to immunization."
Out of the 139 study participants, only two developed severe COVID-19 infections following a full vaccination. One required severe hospitalization 12 weeks after being vaccinated, and the other died, nine weeks after receiving the second dose of the Pfizer vaccine.
The reduced response rates to vaccinations among transplant recipients have been well documented throughout previously published studies covering other common vaccines such as those that protect against hepatitis B, the flu or pneumococcal ones.
While the study confirms previous findings, the researchers note that further research needs to be done to figure out whether or not patients with these low serological levels are at a higher risk of contracting coronavirus, and what the severity of the sickness would be if so, considering there has not been a well-established "protective antibodies threshold."

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Researchers recommend that organ transplant recipients be counseled regarding their own personal immunization, and take an "individual approach" to the matter, in addition to continuing to practice social distancing and other measures to protect themselves against COVID-19 infections.


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