COVID-19(9) systemic(8) SLE(8) Patient(8) Lupus(8) booster vaccination(5) anti-RBD(5) Anti-RBD IgG(5) Arthritis(5) titre(5) variant(5) initial(5) BNT162b2(5) raised(5) Omicron variant(5) inactivated(5) cellular(5) domain(5) immunogenicity(5) Administered(5) vaccination.(5) occurred(5) RBD(5) booster dose(5) Neutralising activity(5) humoral(5) registration number(5) Vaccine(5) positive(5) omicron(5)