Immunogenicity and Safety of Homologous and Heterologous Prime-Boost of CoronaVac and ChAdOx1 nCoV-19 among Hemodialysis Patients: An Observational Prospective Cohort Study.

Background: Vaccines that prevent SARS-CoV-2 infection are considered the most promising approach to modulating the pandemic. There is scarce evidence on the efficacy and safety of different vaccine prime-boost combinations in MHD patients since most clinical trials have used homologous mRNA vaccine regimens.

Methods: This prospective observational study assessed the immunogenicity and safety of homologous CoronaVac (SV-SV), ChAdOx1 nCoV-19 (AZD1222) (AZ-AZ), and the heterologous prime-boost of SV-AZ, among MHD patients.

Results: A total of 130 MHD participants were recruited. On day 28, after the second dose, seroconversion results of the surrogate virus neutralization test were not different between vaccine regimens. The magnitude of the receptor-binding domain-specific IgG was highest among the SV-AZ. Different vaccine regimens had a distinct impact on seroconversion, for which the heterologous vaccine regimen demonstrated a higher probability of seroconversion (OR 10.12; = 0.020, and OR 1.81; = 0.437 for SV-AZ vs. SV-SV, and SV-AZ vs. AZ-AZ, respectively). There were no serious adverse events reported in any of the vaccine groups.

Conclusions: Immunization with SV-SV, AZ-AZ, and SV-AZ could generate humoral immunity without any serious adverse events among MHD patients. Using the heterologous vaccine prime-boost seemed to be more efficacious in terms of inducing immunogenicity.