Immunogenicity and safety of high-dose versus standard-dose inactivated influenza vaccine in rheumatoid arthritis patients: a randomised, double-blind, active-comparator trial

BACKGROUND:Patients with rheumatoid arthritis have increased risk of seasonal influenza and influenza-related complications but have reduced vaccine immunogenicity. It is unknown whether patients with rheumatoid arthritis would benefit from more immunogenic vaccine formulations. This study investigated the immunogenicity and safety of a high-dose trivalent inactivated influenza vaccine (HD-TIV) in patients with rheumatoid arthritis compared to a standard-dose quadrivalent influenza vaccine (SD-QIV). METHODS:This study was a treatment-stratified, randomised, double-blind trial to compare the immunogenicity and safety of SD-QIV (15 μg of haemagglutinin [HA] per strain) versus HD-TIV (60 μg of HA per strain) in adults with rheumatoid arthritis who are positive for rheumatoid factor or anti-cyclic citrullinated peptide, or both, recruited during the 2016-17 and 2017-18 influenza seasons at three hospitals affiliated with McGill University (Montreal, QC, Canada). Participants had received treatment for rheumatoid arthritis with conventional or targeted synthetic disease-modifying antirheumatic drugs (DMARDs) or biological DMARDs, or combinations of them, were still on treatment at the time of enrolment, and their treatment had not been modified during the 3 months before enrolment. They were stratified into one of three groups according to treatment. Patients who, at enrolment, were taking conventional or targeted synthetic DMARDs (methotrexate, hydroxychloroquine, and sulfasalazine) as monotherapy or in combination were stratified to group 1; those who were taking a biological DMARD (anti-tumour necrosis factor or anti-interleukin 6), with or without methotrexate, hydroxychloroquine, or sulfasalazine (or a combination thereof) were stratified to group 2; and those who were taking abatacept, tofacitinib, or rituximab, with or without methotrexate, hydroxychloroquine, or sulfasalazine (or a combination thereof) were stratified to group 3. Participants were randomly allocated (1:1) to receive the SD-QIV or HD-TIV vaccine. Randomisation was based on a computer-generated allocation sequence, and participants, investigators, and research nurses responsible for safety assessments were masked to vaccine assignment. The primary outcome was the seroconversion rate (as measured by haemagglutination-inhibition assay) per strain at day 28. Analysis was done in the modified intention-to-treat population, which included all randomly assigned participants for whom seroconversion status was available. Safety was assessed throughout the surveillance period (day 0-186). This trial is registered at ClinicalTrials.gov, number NCT02936180. FINDINGS:Between Oct 24, 2016, and Dec 6, 2017, 696 patients with rheumatoid arthritis were invited to participate in the study and 279 were randomly assigned and vaccinated (140 [50%] received SD-QIV and 139 [50%] HD-TIV). 136 patients who received SD-QIV and 138 who received HD-TIV were included in the modified intention-to-treat anaysis. Patients who received HD-TIV were more likely to seroconvert than those who received SD-QIV: the odds ratio was 2·99 (95% CI 1·46-6·11) for seroconversion to strain A/H3N2, 1·95 (1·19-3·22) for seroconversion to strain B/Bris, 3·21 (1·57-6·56) for seroconversion to strain A/H1N1 (in 2016-2017), and 2·44 (1·18-5·06) for seroconversion to strain A/H1N1 (in 2017-2018). Similar results were observed in patients from groups 1 and 2; the number of individuals in group 3 was insufficient to draw conclusions. Local and systemic adverse events were similar in both vaccine groups, no serious adverse events were reported between days 0 and 28 in any group, and neither vaccine increased rheumatoid arthritis disease activity. INTERPRETATION:Our data suggest that in patients with seropositive rheumatoid arthritis, HD-TIV is safe and more immunogenic than SD-QIV. These results are the first evidence to support the use of the HD-TIV in these patients. FUNDING:The Arthritis Society-Canada.