Background A monovalent, adjuvanted, inactivated H1N1 influenza vaccine (Pandemrix) was reported as highly immunogenic resulting in seroconversion in 77-94% of adults after administration of a single dose (ref).

Objectives To investigate impact of different anti-rheumatic treatments on antibody response following H1N1 vaccination in patients with rheumatoid arthritis (RA) and spondylarthropathy (SpA).

Methods Patients with arthritis (n=333; mean age 58 years, 66% women) participated. Hemagglutination inhibition (HI) assay was performed on blood samples drawn prior to and after mean 8 months following vaccination. A positive immune response was defined as seroconversion i.e. ≥4-fold increase in HI titer or HI ≥40 in case ofa negative pre-vaccination serum. There were 7 treatment groups: RA on MTX; RA on anti-TNF monotherapy; RA on anti-TNF+MTX; RA on other biologics (abatacept, rituximab, tocilizumab); SpA on anti-TNF monotherapy; SpA on anti-TNF+MTX and SpA on NSAIDs/analgesics.

Results The figure shows percentages of patients with positive immune responses in different treatment groups. RA patients on rituximab had significantly lower (p<0.001) and SpA on anti-TNF monotherapy significantly better response rates compared to other treatment groups (p 0.001-0.032). No significant differences were found between other groups.

Conclusions Rituximab treatment is associated with severely reduced antibody response to the pandemic H1N1 influenza vaccine. Eight months after vaccination, antibody response in SpA patients on anti-TNF monotherapy was still as good as that reported for healthy adults efter 3-4 weeks. All other treatments groups showed lower antibody response.

References Broadbent AJ, Subbarao K. Current Opinion in Virology 2011 (1);4:254-262.

Disclosure of Interest None Declared