TOPLINE:

The adjuvanted respiratory syncytial virus (RSV) vaccine RSVPreF3 was immunogenic in lung transplant (LT) and allogeneic hematopoietic cell transplant (alloHCT) recipients. No vaccine-associated allograft rejection in LT recipients or graft-vs-host disease in alloHCT recipients was reported.

METHODOLOGY:

• Researchers conducted a prospective study at the University Health Network to assess immune responses to the adjuvanted RSVPreF3 vaccine in adult alloHCT and LT recipients who were at the highest risk for severe RSV infection.
• They included 46 alloHCT recipients (median age at vaccination, 64 years; 65.2% men) and 40 LT recipients (median age, 59 years; 55% men) who completed the vaccination between September 19, 2024, and February 7, 2025, and were followed up for a median of 191 and 192 days, respectively.
• The primary outcome was neutralizing antibody (NAb) levels (expressed as NT95 titer, which is the reciprocal of the highest serum dilution capable of inhibiting at least 95% viral infection) at baseline and 4-6 weeks post-immunization.
• Other measurements included levels of anti-RSV prefusion (PreF) immunoglobulin (Ig) G-binding antibodies and RSV-specific T cells, along with monitoring of vaccine-related adverse events through participant diaries.

TAKEAWAY:

• NAb responses increased significantly in both groups, with median NT95 titers rising from 128 to 512 in LT recipients and from 64 to 192 in alloHCT recipients (P < .0001 for both).
• Median levels of anti-RSV PreF IgG-binding antibodies were elevated significantly, from 46,558 to 153,376 AU/mL in LT recipients (P = .0018) and from 12,279 to 28,353 AU/mL in alloHCT recipients (P = .0015).
• Vaccine-specific polyfunctional CD4+ T-cell responses were robust; they increased significantly post-vaccination (P < .0001) and were observed in 80.0% of LT recipients and 71.4% of alloHCT recipients.
• No cases of vaccine-associated lung allograft rejection in LT recipients or unexplained cytopenia or graft-vs-host in alloHCT recipients were reported. Three LT recipients developed RSV infection post-vaccination, two of whom required hospitalization.

IN PRACTICE:

“The data suggest that while a single dose may not induce robust NAb responses, the vaccine is well tolerated and capable of stimulating broad CD4+ T-cell responses. Given the high burden of RSV disease and limited treatment options, vaccination remains a promising strategy,” the authors of the study wrote.

SOURCE:

The study was led by Victoria G. Hall, Division of Infectious Diseases, University Health Network in Toronto, Ontario, Canada. It was published online on September 25, 2025, in Clinical Microbiology and Infection.

LIMITATIONS:

The study used a sample size of convenience and was not powered to assess vaccine efficacy or clinical outcomes such as RSV-related hospitalization. The relatively short follow-up period limited the ability to evaluate long-term immunogenicity and durability of protection. The modest sample size may have precluded the identification of clinical factors associated with seroconversion.

DISCLOSURES:

This study received investigator-initiated support from the PSI Foundation and the Ajmera Transplant Centre. Some authors reported receiving financial support from and having other ties with various organizations and companies including the National Health and Medical Research Council, the Government of Victoria, the Canadian Institutes of Health Research, the PSI Foundation, and Moderna.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.