In addition to the new infection risk formula, researchers at Wake Forest Baptist Medical Center in Winston-Salem, N.C., are looking at other characteristics that affect an RA patient’s infection risk. Karen Haas, PhD, assistant professor of microbiology and immunology is conducting a study on how low levels of a key protein, C4, may affect the risk of infection with the Streptococcus pneumoniae bacterium, even in those who are vaccinated. This bacterium can be dangerous for people with RA or lupus. If inhaled from the air, the bacterium can cause respiratory pneumonia. If it gets into the person’s blood stream, it can cause a serious septic infection, says Haas.

C4 is one important element of increased susceptibility to infection in people with autoimmune diseases, says Haas. People with autoimmune diseases like systemic lupus erythematosus, for example, may show low levels of the protein during bad flares, she says.

The mice in the Wake Forest study were vaccinated against S. pneumoniae just like many humans with RA, says Haas. “Mice with low levels of C4 had a good antibody response to the vaccine,” she says.

The mice were then exposed to the bacterium either through the respiratory tract or through their bloodstream. In initial observations, the vaccinated mice fought off the dangerous blood infection.

“We had thought that the vaccine had to work with C4 to produce antibodies,” but that may not be the case according to this early research, says Haas. “Then we gave S. pneumoniae to them through the nose, the typical way we’d pick up bacteria. The vaccine did not protect them. They got very bad cases of pneumonia.”

So people with RA may still be at higher risk of bacterial infections even if they are vaccinated, this preliminary research seems to suggest. “Even though you are getting vaccinated, and you are getting a good antibody response, if you have low levels of C4, you may be deficient in your defense against lung bacteria,” says Haas. This study, funded in part by the Arthritis Foundation, is still in its early stages, so it’s unclear how C4 may play a role in the infection risk of people with RA who are vaccinated.

At this time, physicians recommend that people with RA get annual vaccinations and use preventive measures like regular hand washing or avoiding other people with infections if possible, says Dr. Matteson.

“If you have RA, your infection risk is double anyway, so it is really important to have identified those characteristics that the patient has, and to tell them that they have to take particular care if they are running a fever, have a cough, or have a burning sensation when they urinate,” says Dr. Matteson.

RA patients with any of these symptoms of infection should contact their health-care professional right away for treatment, he adds.