# Longitudinal evaluation of anti-SARS-CoV-2 neutralizing antibody levels in 3-dose homologous (mRNA-1273- mRNA-1273- BNT162b2) vaccinated kidney transplant population: 18-month follow-up

## TL;DR

This study shows that kidney transplant recipients who received three doses of an mRNA-based COVID-19 vaccine maintained strong antibody levels for 18 months, especially if they had prior infection.

## Contribution

The study provides 18-month longitudinal data on neutralizing antibody levels in kidney transplant recipients after a three-dose mRNA vaccine regimen.

## Key findings

- Kidney transplant recipients with prior infection had consistently high neutralizing antibody levels over 18 months.
- Those without prior infection showed lower initial responses but achieved high antibody levels by 12 months post-third dose.
- Both groups had similar high antibody levels at 12 months post-third dose.

## Abstract

•Kidney transplant recipients with prior COVID-19 had high neutralizing antibody levels throughout an 18-month follow-up.•Kidney transplant recipients without prior infection showed lower responses and de novo seroconversion.•Both groups had similar, high neutralizing antibody levels at 12 months post-third dose.

Kidney transplant recipients with prior COVID-19 had high neutralizing antibody levels throughout an 18-month follow-up.

Kidney transplant recipients without prior infection showed lower responses and de novo seroconversion.

Both groups had similar, high neutralizing antibody levels at 12 months post-third dose.

This study aimed to assess the immune response to a three-dose primary series of COVID-19 vaccination in kidney transplant recipients (KTRs), a population vulnerable to infection due to immunosuppression.

This study was a longitudinal evaluation of neutralizing antibody (nAB) dynamics in 43 KTRs in a lower-middle-income setting receiving a three-dose homologous (messenger RNA [mRNA]-1273-mRNA-1273- BNT162b2) vaccination against COVID-19. Samples were obtained at time points (TP) as follows: TP0, pre-vaccination; TP1, 1-month post-first dose (mRNA-1273); TP2, 1-month post-second dose (mRNA-1273); TP3, 4 months post-second dose; TP4, 2 weeks post-third dose (BNT162b2); TP5, 5 months post-third dose; and TP6, 12 months post-third dose. Anti-SARS-CoV-2 nAB were detected using the Genscript cPassTM pseudoviral neutralization kit. Demographic and clinical details were obtained through interviewer-administered questionnaires.

Pre-vaccination serum analysis showed n = 7 KTRs had prior COVID-19 infection, classified as ‘infected + vaccinated,’ while others were ‘vaccinated.’ Both groups were similar in age (41.7 years vs 46.7 years, P = 0.2383), gender, and transplant characteristics. Seroconversion and mean/ median antibody level (MAB) in the vaccinated and infected + vaccinated KTRs were: TP1, 8.3% vs 100% (P <0.001), MAB = 64.3 IU/mL vs 1424 IU/mL (P = 0.0167); TP2, 52.7% vs 100% (P = 0.0194), MAB = 175 IU/mL vs 2790 IU/mL (P <0.0001); TP3, 100% vs 100%, MAB = 106IU/mL vs 2153 IU/mL (P = 0.0002); TP4, 100% vs 100%, MAB = 736 IU/mL vs 2152 IU/mL (P = 0.0307); and TP6, 100% vs 100%, MAB > 2565 IU/mL vs > 3028 IU/mL (P = 0.5238). No factors were associated with seroconversion or MAB.

KTRs receiving a three-dose mRNA COVID-19 vaccine regimen maintained strong nAB levels at 1-year follow-up, with comparable antibody levels seen between KTRs with prior infection + vaccination and vaccination alone.