Clinical Effectiveness of SARS-CoV-2 Vaccination in Renal Transplant Recipients. Antibody Levels Impact in Pneumonia and Death.

Background: Few studies have described the clinical impact of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines in renal transplant recipients (RTRs) in the context of omicron variant and the third vaccine dose. Antibody titer has been tried to relate to the prediction of outcomes related to SARS-CoV-2, but it results controversially in these populations.

Methods: All patients with positive SARS-CoV-2 polymerase chain reaction followed at a RTRs reference center from March 15, 2020, to March 15, 2022, were considered for analysis. Cases were analyzed by vaccination status. Breakthrough cases were then analyzed by nonantibodies (<20 arbitrary unit [AU]/mL), low (20-100 AU/mL), and high antibody titers (>100 AU/mL) against SARS-CoV-2 spike protein. Outcomes included pneumonia and mortality. We used logistic regression multivariable to assess for confounders.

Results: Among 186 RTRs with coronavirus disease 2019, 50.5% (n = 94) were vaccinated versus 49.5% (n = 92) unvaccinated. Of the vaccinated patients, 67.02% developed a high antibody titer (>100 AU/mL) but 14.89% achieved a low antibody titer and 18.08% nonantibodies. Pneumonia-free survival (day 20) was 95% in high antibody titer but 40% in unvaccinated RTRs. Survival in RTRs at day 60 was similar in the unvaccinated group compared with nonantibodies breakthrough cases (82%) but 92% in the low antibody titer group (relative risk, 0.027; 95% confidence interval, 0.002-0.479; P = 0.014). Only patients with >100 AU/mL showed a 100% survival on day 60 postinfection.

Conclusions: Vaccinated RTRs who achieve at least a low antibody titer (>20 AU/mL) had better results in terms of pneumonia and mortality than unvaccinated RTRs. Antibody titer >100 AU/mL associate with even better results than patients with lower antibody titers.