Solid organ transplant (SOT) recipients may remain at relatively high risk for COVID-19 despite receiving the first dose of mRNA vaccines against the virus that causes the disease, according to investigators.

In a study of immunogenicity of the first dose of the mRNA SARS-CoV-2 vaccine, Brian J. Boyarsky, MD, of Johns Hopkins University School of Medicine in Baltimore, Maryland, and colleagues found that most of the 436 recipients in the study did not mount appreciable anti-spike antibody responses.

Of the 436 patients — including 229 kidney transplant recipients — 52% received the vaccine made by Pfizer-BioNTech and 48% received the vaccine made by Moderna. Both vaccines are designed to stimulate an immune response to part of the SARS-CoV-2 spike protein. Two doses of each vaccine are required for full protection against the virus. 

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At a median of 20 days after the first dose of the vaccine, antibody was detected in 76 (17%) patients, Dr Boyarsky and colleagues reported in a research letter published online in JAMA. Older patients were less likely to have an antibody response, with the likelihood of response decreasing by 17% for each 10-year increase in age. SOT recipients receiving anti-metabolite maintenance immunosuppression therapy were less likely to develop an antibody response than those not receiving this therapy (37% vs 63%). An antibody response was more likely to develop among patients receiving the Moderna vaccine than those receiving the Pfizer-BioNTech vaccine (69% vs 31%).

The investigators noted that their results contrast with the robust early immunogenicity observed in mRNA vaccine trials, including 100% anti-spike seroconversation by day 15 following vaccination with the Moderna vaccine and by day 21 following vaccination with the Pfizer-BioNTech vaccine.

“Deeper immunophenotyping of transplant recipients after vaccination, including characterization of memory B-cell and T-cell responses, will be important in determining vaccination strategies as well as immunologic responses after the second dose,” the authors concluded.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Boyarsky BJ, Werbel WA, Avery RK, et al. Immunogenicity of a single dose of SARS-CoV-2 messenger RNA vaccine in solid organ transplant recipients. Published online March 15, 2021. JAMA. doi:10.1001/jama.2021.4385