Antibody Responses to an Additional Dose of SARS-CoV-2 mRNA Vaccine in Solid Organ Transplant Recipients with and without HIV

ABSTRACT

Purpose: Solid organ transplant (SOT) recipients mount suboptimal immune responses to a two-dose SARS-CoV-2 mRNA vaccine series. Data regarding antibody responses in HIV and SOT remains limited. We characterized spike binding antibody responses before and after an additional mRNA vaccine dose in SOT recipients, including in people with HIV (PWH). Method(s) Spike binding antibody titers were assessed before and one month after an additional vaccine dose using a quantitative ELISA. An additional vaccine dose was defined as a third dose of a mRNA vaccine primary series, as recommended by the CDC. Result(s) Antibody titers were assessed in 64 SOT recipients (58% kidney, 34% liver, 8% other). Participants had a median age of 57 and 47% were women. PWH comprised 14% of the cohort (9/64, 78% kidney). 70% (45/64) of SOT recipients developed antibodies after a two-dose vaccine series (62% kidney, 33% liver). The additional dose was given a median of 169 days (IQR 144.75-185.75 days) after the second vaccine dose, and 72% received three doses of BNT162b2 (Pfizer-BioNTech) while 28% received three doses of mRNA-1273 vaccine (Moderna). The median time between transplantation and an additional vaccine dose was 2.8 years (IQR, 0.6-8.9). 32% (6/19) of SOT recipients who had no detectable antibody seroconverted after receiving an additional vaccine dose. The 45 participants who were seropositive prior to the third dose displayed a median 4.4-fold increase in antibody titers. SOT recipients with HIV had comparable antibody responses to those without HIV. Conclusion(s) Our data indicate that SOT recipients benefit from an additional SARS-CoV-2 mRNA vaccine dose. SOT recipients with and without HIV appear to mount comparable antibody responses upon vaccination, although larger numbers are needed.