Patients with rheumatoid arthritis (RA) are at increased risk of infections if anaemia or lymphopenia are present at diagnosis, according to a UK study.

Pneumonia was also more common in people with RA and there was no evidence of a protective effect for pneumococcal vaccine.

The results, published in Rheumatology, did provide important evidence that influenza vaccination is effective in people with RA.

According to the researchers, led by Professor of Rheumatology Karim Raza from the University of Birmingham, the data showed robust associations between haematological markers and risk of common infections in early RA.

“This suggests haematological markers may be clinically useful to identify individuals who might benefit from targeted counselling to stress the importance of early presentation if symptoms of infection develop,” they said.

The study investigated the prevalence of haematological abnormalities (anaemia, neutropenia and lymphopenia) in 6,591 people with RA at the point of diagnosis in primary care. Rates of infection were compared with a matched cohort of 3,699 patients without RA, along with the influence of vaccination status (influenza and pneumococcal) on rates of common infections.

Anaemia was common at diagnosis (16.1%), with neutropenia (0.6%) and lymphopenia (1.4%) less so. Anaemia and lymphopenia, but not neutropenia, were associated with increased infection risk. The lack of an association between neutropenia and infection might be due to the very low numbers of patients with the condition, the authors said.

Pneumococcal immunisation rates were low (16% and 12% in RA and non-RA groups) and there was no significant benefit of vaccination against pneumococcal infection in patients with RA.

The researcher postulated that the apparent lack of efficacy of the pneumococcal vaccine in people with RA might relate to a lack of data on specificity of infection serotype to match with vaccine serotype. Further studies, ideally in confirmed pneumococcal disease, are needed to determine the efficacy of pneumococcal vaccination in people with RA and look at how effectiveness is modified by RA therapy, they said.

Influenza immunisation rates were 64% in the RA patient group and 48% in the non-RA group. Flu vaccine was associated with a 41% reduction in flu-like illness (Hazard Ratio 0.59) in those with RA while there was no evidence the vaccine reduced the risk of flu in people without RA (HR 0.95).

With this in mind, the researchers said further studies exploring rates of annual flu vaccine uptake among people with RA and reasons for not getting vaccinated would be useful to improve vaccination rates.

“Our study provides important real-world evidence that the influenza vaccine is effective in people with RA,” they concluded.