Responses to flu vaccines in 340 RA patients in regular follow-up compared to 234 healthy patients were assessed in a Brazilian hospital-based study.
Measures of protection obtained by vaccination (seroprotection rate (SP)) after immunization was over 20% lower for RA patients compared to healthy individuals (60.1% vs. 82.9% comparatively (p<0.001)). Tests to determine levels of detectable antibodies to microorganisms in the blood serum as a result of infection and immunization with the flu virus (seroconversion rate (SC)) showed a similar pattern with 53.4% of RA patients and 76.9% of healthy controls having antibodies present respectively (p<0.001).
"This study has highlighted that there are differences in the level of protection between the H1N1 vaccine and the seasonal influenza vaccine so healthcare professionals should not assume that immune response will be the same with different vaccines" said Professor A. Ribeiro of the University of Sao Paolo. "In planning for future pandemic outbreaks, healthcare professionals should consider specific immunization strategies to ensure this large population of patients are as fully protected as possible from the risk of contracting pandemic flu."
The vaccination's impact on disease activity (DAS28*) was also measured and nine patients (2.6%) reported worsening of symptoms with the mean disease activity score changing from 3.66 to 5.15 (p<0.05) after the H1N1 vaccination. No serious adverse events were seen across either patient group, although more subjects in the RA patient group reported more adverse events, 42% versus 30.8% with a rate of 140 events/100 patients versus 87/100 control group (p<0.005).
* DAS28 (Disease Activity Score) is an index used by physicians to measure how active an individual's RA is. It assesses number of tender and swollen joints (out of a total of 28), the ethroycyte sedimentation rate (ESR, a blood marker of inflammation), and the patient's 'global assessment of global health'. A higher score indicates more active disease.