In kidney transplant recipients who did not develop SARS-CoV-2 antibodies after standard vaccination, switching from an mRNA vaccine to the viral vector vaccine for the third dose does not boost efficacy, according to trial findings.

In the randomized trial of 197 kidney transplant recipients with no response after 2 doses of an mRNA (mean age 61.2 years; 42% women), only 39% developed SARS-CoV-2 antibodies after a third vaccine dose, Rainer Oberbauer, MD, PhD, of Medical University of Vienna, Vienna, Austria, and colleagues reported in JAMA Internal Medicine. The odds of antibody response (more than 0.8 U/mL after 4 weeks) did not differ significantly between the 99 and 98 patients randomly assigned to a third dose of either an mRNA vaccine (PfizerBioNTech’s BNT162b2 or Moderna’s mRNA-1273) or the viral vector vaccine (Janssen’s Ad26COVS1), respectively: 35% vs 42%.

Only 22% of seroconverted patients displayed neutralizing antibodies, the investigators reported. T-cell response occurred in only 17 patients with no between-group differences.

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The third dose of an mRNA vaccine was associated with a higher frequency of local injection site pain compared with the vector vaccine, but systemic symptoms were comparable. Five serious adverse events occurred but were not related to vaccination.

Patients not receiving triple maintenance immunosuppression had significant 3.6-fold increased odds of developing antibodies after a third vaccine dose, the investigators reported. Each doubling of years since kidney transplantation was also significantly associated with 1.4-fold increased odds of vaccine response.

Each doubling of torque teno virus plasma levels — a marker of the overall state of the immune system after organ transplantation — was significantly associated with 8% decreased odds of response.

A recent case series published in the Annals of Internal Medicine concluded that a fourth dose of an mRNA COVID-19 vaccine increases antibody response in kidney transplant recipients with a weak response after 3 doses.

“Other immunization strategies may include temporarily reducing maintenance immunosuppression or prophylaxis with long-acting recombinant neutralizing antibodies that successfully reduce viral load in patients without protective immunity and which may convey passive immunity for several months,” according to Dr Oberbauer’s team.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.


Reindl-Schwaighofer R, Heinzel A, Mayrdorfer M, et al. Comparison of SARS-CoV-2 antibody response 4 weeks after homologous vs heterologous third vaccine dose in kidney transplant recipients: a randomized clinical trial. JAMA Intern Med. 182(2):165-171. doi:10.1001/jamainternmed.2021.7372