Earlier research found that only 17 percent of organ transplant patients had a positive antibody response to the first dose of the SARS-CoV-2 messenger RNA (mRNA) vaccines. New research explored the antibody response after the second dose of the vaccine.*

What the Researchers Did

Researchers analyzed 658 transplant recipients without prior polymerase chain reaction–confirmed COVID-19 who completed the 2-dose SARS-CoV-2 mRNA vaccine series between December 16, 2020, and March 13, 2021. They were tested for antibodies, and the proportion of patients who developed a positive antibody response was assessed using the Fisher exact test and the Kruskal-Wallis test to ensure accuracy. 

What the Researchers Found

Of the 658 participants, the researchers found that:

• 98 (15%) had measurable antibody response after dose one and dose two
• 301 (46%) had no antibody response after dose one or dose two 
• 259 (39%) had no antibody response after dose one but subsequent antibody response after dose two

Getting even more granular, they found that 473 (of the 658) transplant recipients who were on antimetabolite therapies, which are immunosuppressive therapies, had an even lower response to the vaccine—with 8% having antibodies after dose one and two. Additionally, the 185 participants not on antimetabolite therapy had a higher antibody response after dose one and dose two at 32%.

What the Findings Mean

Many participants saw a boost in antibodies after the second dose. However, patients who are on immunosuppressive therapy do not respond as well to SARS-CoV-2 mRNA vaccines. Therefore, many patients are left vulnerable to the effects of COVID-19 despite having been vaccinated.

The study had several limitations, including limited assessment of post-vaccination SARS-CoV-2 and a lack of incorporation of memory B-cell or T-cell responses, which also play a role in warding off viruses.

Future studies should explore more options for improving immune response in transplant recipients, such as additional booster doses or immunosuppression modulation.

*Boyarsky BJ, Werbel WA, Avery RK, et al. Antibody Response to 2-Dose SARS-CoV-2 mRNA Vaccine Series in Solid Organ Transplant Recipients. JAMA. Published online May 05, 2021. doi:10.1001/jama.2021.7489