Starting a tumor necrosis factor-alpha inhibitor, or anti-TNF, doesn’t increase a patient’s risk of serious infections requiring hospitalization any more than starting a non-biologic disease modifying drug, according to a study published online in November in the Journal of the American Medical Association.

The side-effect profile of anti-TNFs, biologic drugs used to treat rheumatoid arthritis, or RA, and other autoimmune conditions, has been a concern to doctors, researchers and patients alike since the first one was introduced about 13 years ago. Because anti-TNFs suppress the immune system, the drugs increase the risk of infections. And because they are relatively new, the long-term risk of side effects isn’t yet known. Anti-TNF drugs include infliximab, or Remicade; etanercept, or Enbrel; adalimumab, or Humira; certolizumab pegol, or Cimzia; and golimumab, or Simponi.

“We hope [the research] provides some clarification and some reassurance for patients and providers,” says lead study author Carlos G. Grijalva, MD, an assistant professor of preventive medicine at Vanderbilt University in Nashville, Tenn.

Previous studies of the severity of anti-TNF side effects have had mixed results, with the worry extending beyond infections to cancer. The cancer risk was put into perspective by several recent studies, including a meta-analysis published online in September in the Annals of Rheumatic Diseases, which found anti-TNFs slightly elevated the risk of skin cancer but not other cancers.

But in that same month, the U.S. Food and Drug Administration strengthened the warning label on the drugs to include an elevated risk of infection from two additional types of bacteria, Legionella and Listeria. And a British study published in June in the journal Rheumatology found the risk of infections associated with anti-TNFs is “highest during the first six months of therapy.”

“Some previous studies have suggested most of the potential increased risk would be concentrated right after initiation, so we set up our study to look at the frequency of infection in the first year, with that idea in mind,” Dr. Grijalva explains.

He and his team collected and analyzed 10 years’ worth of records on more than 32,000 patients with RA, inflammatory bowel disease, or IBD, psoriasis and spondyloarthropathies from several large databases – national Medicaid and Medicare, Tennessee Medicaid, Kaiser Permanente Northern California and pharmaceutical assistance programs in New Jersey and Pennsylvania.