Abstract
Immunogenicity data on the mRNA SARS-CoV-2 vaccine booster after completing a primary series vaccination, other than the mRNA vaccine, in patients with autoimmune rheumatic diseases (ARDs) is scarce. In this study, we reported the humoral immunogenicity of an mRNA booster 90-180 days after completing heterologous CoronaVac/ChAdOx1 nCoV-19 (n = 19) or homologous ChAdOx1 nCoV-19 (n = 14) vaccination by measuring the anti-SARS-CoV-2 receptor binding domain (RBD) IgG levels at one and three months after mRNA booster vaccination. This study included 33 patients with ARDs [78.8% women; mean (SD) age: 42.9 (10.6) years]. Most patients received prednisolone (75.8%, mean [IQR] daily dose: 7.5 [5, 7.5] mg) and azathioprine (45.5%). The seropositivity rates were 100% and 92.9% in CoronaVac/ChAdOx1 and ChAdOx1/ChAdOx1, respectively. The median (IQR) anti-RBD IgG level was lower in the ChAdOx1/ChAdOx1 group than in the CoronaVac/ChAdOx1 group (1867.8 [591.6, 2548.6] vs. 3735.8 [2347.9, 5014.0] BAU/mL, p = 0.061). A similar trend was significant in the third month [597.8 (735.5) vs. 1609.9 (828.4) BAU/mL, p = 0.003]. Minor disease flare-ups occurred in 18.2% of the patients. Our findings demonstrated satisfactory humoral immunogenicity of mRNA vaccine boosters after a primary series, with vaccine strategies other than the mRNA platform. Notably, the vaccine-induced immunity was lower in the ChAdOx1/ChAdOx1 primary series.