Seroconversion in liver and intestine transplant patients after one, two or three doses of adenoviral vector vaccines against SARS-CoV-2: Single center experience in Argentina

Background: The capacity of different anti‐SARS‐CoV‐2 vaccines to elicit immune response is not equivalent in the healthy population compared to chronically immunosuppressed patients. Most of the reports available to assess the effects of anti‐SARS‐CoV‐2 vaccines on solid organ transplant recipients (SOTR) were performed using mRNA‐based vaccines. Objective: This study aims to assess the seroconversion rate in a cohort of liver and liver‐ intestinal transplant patients after vaccination with the non‐replicative vector‐based vaccines after transplantation used in our country, Argentina (rAd26‐rAd5 (Sputnik V) and ChAdOx11 nCoV‐19 (AZD1222) (Astra Zeneca‐Oxford). Methods: One hundred and three (103) liver and liver‐intestinal transplant recipients were enrolled. Patients with previous PCR‐confirmed COVID19 were excluded, therefore 77 were finally included for analysis; 75 were liver transplant recipients, 1 was a combined liver‐intestine and 1 a multivisceral transplant. All received their first vaccine dose between March and June 2021; 66,2% males, and the mean age was 56,3 years. All patients have a post‐transplant follow up longer than 1 year (mean 6.6 years, median 5 years, range 1–23 years). Immune response after first, second and third doses were determined using three different spike (S)‐S commercial ELISA kits and an in‐house made anti nucleocapsid‐protein (N) ELISA. Results: Following the three doses, 57.1 % (44/77) of the patients seroconverted, while 33/77 (42.9 %) did not present anti‐SARS‐CoV‐2 antibodies. The seroconversion rate was different for each dose. We found that 5/27 (18.5 %) of transplant patients seroconverted after a single dose; 18/29 pts (62.0 %) had anti‐SARS‐Cov‐2 antibodies after the second doses; and 18/21 pts (85.7 %) reached the seroconversion after the third doses. The proportion of seroconversion was significantly increased in the second doses regardless the response observed after the first doses (p = 0.012, Fisher’s exact test), particularly when two doses of ChAdOx11 vaccine was administrated (p = 0.040, Chi‐square). However, the comparisons of seroconversion rate between Sputnik V and ChAdOx11 vaccines showed no differences after the different vaccination doses. No significant statistical difference in patient´s gender, age, comorbidities, type of vaccine, post‐transplant, or maintenance immunosuppressive therapy was found between responders and non‐responders. Conclusion: Despite having a lower seroconversion rate compared to the general population, viral‐vector vaccines benefit SOTR patients increasing the seroconversion rate using at least two doses of vaccine. These results support the concept of developing tailor‐made vaccination guidelines for this specific population. This analysis provides further support to safety and efficacy of viral‐vector vaccines in liver and liver‐intestine transplant patients. Fil: Yantorno, Silvina. Fundación Favaloro; Argentina Fil: Curciarello, Renata. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Estudios Inmunológicos y Fisiopatológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Estudios Inmunológicos y Fisiopatológicos; Argentina