Abstract
Despite receiving an annual influenza vaccination, lupus patients showed a decline in immunological responses for various reasons. This study aimed to assess immune responses after booster- (BD) and standard-dose (SD) quadrivalent influenza vaccine and the adverse events and incidence of influenza infection among lupus patients. A randomized controlled trial was conducted between March 2021 and May 2022 at Ramathibodi Hospital. All lupus patients were stratified into two groups depending on the depth of immunosuppressive therapy and randomized to receive either BD or SD. Hemagglutination inhibition assay (HAI) before vaccination and 4 weeks after completion of the vaccination series were assessed. The incidence of influenza infection and vaccine-associated adverse events were recorded. A total of 109 lupus patients completed the HAI analysis. 54/109 patients were in high- (HI), and 55/109 were in low-level immunosuppressive (LI) groups. Focusing at the rates to achieve HAI ≥ 1:160, in the LI group, the rates after SD were 85.5% for H1N1, 69.2% for H3N2/Hongkong, 82.8% for H3N2/Cambodia, 85.5% for B/Victoria, and 81.8% for B/Yamagata. After BD, the HAI titer rates of ≥ 1:160 cut point were increased in all strains, approaching 100%, similar to the HI group. There was one documented influenza infection during the 12-month follow-up period in LI who received SD. No serious adverse events associated with influenza vaccination were recorded. A booster dose of influenza vaccination may provide a higher HAI titer among lupus patients. The booster influenza vaccine regimen was considered safe in the BD group. Thai Clinical Trials Registry: TCTR20230610003.