Background/Purpose: To assess the effectiveness of inactivated influenza vaccine (IIV) in preventing influenza like illness (ILI), lower respiratory tract infection (LRTI), pneumonia, chronic obstructive pulmonary disease (COPD) exacerbation and death in adults with autoimmune rheumatic diseases (AIRDs).

Methods: Adults with AIRDs e.g. RA, Spondyloarthropathy, SLE etc., and treated with immunosuppressive drugs in the 3 month period before the 1^st September of each year, 2006-2009, and 2010-2015 were identified in the Clinical Practice Research Datalink (CPRD). CPRD is a longitudinal anonymised electronic database containing health records of over 13 million people, registered with >680 general practice surgeries in the UK. It contains details of all diagnoses, prescriptions, immunisations etc. recorded as part of usual medical care. Data for this study were extracted from the CPRD, and from linked Hospital Episode Statistics and Office for National Statistics databases. The 2009-2010 influenza pandemic period was excluded due to co-vaccination with pandemic vaccine and predominance of pandemic virus in community. Propensity score (PS) for vaccination on the 1^st September of each year was calculated using previously published and validated methods. Cox-proportional hazard ratio (HR) and 95% confidence intervals (CIs) were calculated to examine association between vaccination and first occurrence of each outcome of interest upto 31^st August of the next year. Vaccination was regarded as a time-varying covariate, and the protected period began 14 days from the date of vaccination. Sensitivity analysis restricting to the period in which the flu virus was in circulation in the community was performed. The exposure and outcome variables reverted to unexposed and no-outcome on the 1^st September of each year. The association was adjusted for PS for vaccination, year, and included a clustering term to account for data from same participant in multiple years. Stata v14 was used for data analyses.

Results: Data for 30,788 participants (66% female), 76% with RA, 61% treated with methotrexate, and contributing 125,034 person-seasons were included. PS for vaccination predicted vaccination status (area under the curve 0.87). Vaccination reduced the risk of hospitalization for pneumonia, hospitalization for COPD exacerbation, all-cause mortality and death due to pneumonia in that flu season (aHR(95%CI) 0.59(0.51-0.69), 0.59(0.44-0.80), 0.52(0.47-0.59), 0.47(0.35-0.63) respectively). Vaccination also reduced the risk of primary care consultation for ILI (aHR (95%CI) 0.75 (0.60-0.95)) when the analysis period was restricted to the time when influenza viruses circulated. Other protective effects also remained statistically significant in this restricted analysis. These associations did not change when seasons with exposure to sulfasalazine alone were excluded. IIV did not reduce the risk of primary care consultations for LRTI and COPD exacerbations.

Conclusion: This is the first study to demonstrate and quantify the effectiveness of IIV in people with AIRDs. The results provide justification to educate health professionals and actively promote flu vaccination to the immunosuppressed people with AIRDs.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/inactivated-influenza-vaccine-prevents-respiratory-infections-and-improves-all-cause-and-cause-specific-mortality-in-immunosuppressed-people-with-autoimmune-rheumatic-diseases-propensity-score-adjust/