Pandemic non-adjuvanted influenza A H1N1 vaccine in a cohort of patients with systemic sclerosis.

Objective: To assess the possible effect of therapy, disease subtype and severity on H1N1 immunogenicity in patients with SSc.

Methods: Ninety-two patients and 92 age- and gender-matched healthy controls received adjuvant-free influenza A/California/7/2009 (pH1N1) vaccine. Blood samples were collected immediately before and 3 weeks after vaccination to evaluate antibody responses to the H1N1 virus. Efficacy was assessed by seroprotection (SP) and seroconversion (SC) rates and the factor increase in geometric mean antibody titre. Participants received a 21-day symptom diary card and were instructed to report local and systemic adverse events.

Results: SSc patients were predominantly females (91%) and 61% had limited SSc, 12% had severe skin involvement and 57.6% were on immunosuppressive (IS) therapy. SSc patients and controls presented comparable overall SP (P = 0.20) and SC (P = 0.61) rates. Further evaluation of the possible effect of disease and therapy revealed similar rates of SP and SC in patients with dcSSc vs lcSSc (SP P = 0.62 and SC P = 0.66), severe vs mild/moderate skin involvement (SP P = 1 and SC P = 0.45) and with vs without IS (SP P = 0.26 and SC P = 0.10). The frequency of mild local and minor systemic reactions was similar in patients with dcSSC vs lcSSc (P = 0.70 vs 0.32) and in those with and without severe skin involvement (P = 0.59 vs 0.28).

Conclusion: The non-adjuvanted influenza H1N1 virus vaccine proved to be safe and effective, independent of SSc clinical subtype, disease severity or therapy. These latter factors do not seem to contribute to mild adverse events observed in SSc. Our data support the annual influenza vaccination recommendation for these patients.

Trial Registration: ClinicalTrials.gov (http://clinicaltrials.gov), NCT01151644.