Impact of Omicron BA.1 infection on BA.4/5 immunity in transplant recipients

Am J Transplant. 2023 Feb;23(2):278-283. doi: 10.1016/j.ajt.2022.10.004. Epub 2023 Jan 12.


Mutations in the spike protein of SARS-CoV-2 have allowed Omicron subvariants to escape neutralizing antibodies. The degree to which this occurs in transplant recipients is poorly understood. We measured BA.4/5 cross-neutralizing responses in 75 mostly vaccinated transplant recipients who recovered from BA.1 infection. Sera were collected at 1 and 6 months post-BA.1 infection, and a lentivirus pseudovirus neutralization assay was performed using spike constructs corresponding to BA.1 and BA.4/5. Uninfected immunized transplant recipients and health care worker controls were used for comparison. Following BA.1 infection, the proportion of transplant recipients with neutralizing antibody responses was 88.0% (66/75) against BA.1 and 69.3% (52/75) against BA.4/5 (P = .005). The neutralization level against BA.4/5 was approximately 17-fold lower than that against BA.1 (IQR 10.6- to 45.1-fold lower, P < .0001). BA.4/5 responses declined over time and by ≥0.5 log10 (approximately 3-fold) in almost half of the patients by 6 months. BA.4/5-neutralizing antibody titers in transplant recipients with breakthrough BA.1 infection were similar to those in immunized health care workers but significantly lower than those in uninfected triple-vaccinated transplant recipients. These results provide evidence that transplant recipients are at ongoing risk for BA.4/5 infection despite vaccination and prior Omicron strain infection, and additional mitigation strategies may be required to prevent severe disease in this cohort.

Keywords: clinical research/practice; complication: infectious, infection, and infectious agents – viral: SARS-CoV-2/COVID-19; infectious disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Neutralizing
  • Antibodies, Viral
  • Biological Assay
  • Breakthrough Infections
  • COVID-19* / epidemiology
  • Humans
  • SARS-CoV-2
  • Transplant Recipients


  • Antibodies, Neutralizing
  • Antibodies, Viral