Staphylococcus colonization of atopic dermatitis patients’ skin is associated with a weaker response to intradermal flu shots, according to a new study which suggests that intramuscular flu vaccines may be more effective in this group.

The research, funded by the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, is being published online in the Journal of Allergy and Clinical Immunology.

Researchers evaluated 202 patients with atopic dermatitis, and 134 control patients, vaccinating 136 of them with intradermal vaccines and the rest with intramuscular vaccines. The vaccines included proteins from three strains of influenza (influenza B, H1N1 and H3N2). They assessed response to the vaccine 28 days after vaccination by measuring levels of various antibodies in the blood. Eighty-four (42 percent) of the atopic dermatitis patients had positive skin swabs for Staphylococcus aureus colonization.

Overall, the atopic dermatitis patients responded similarly to the non-atopic patients to both intramuscular (IM) and intradermal (ID) vaccines. However, a significant difference was seen in patients with atopic dermatitis who were colonized with Staphylococcus aureus and vaccinated against influenza B. Only 11 percent of patients given the ID vaccine developed protection against influenza B compared to 47 percent who received the IM vaccine. The intradermal vaccine also generated less protection against H1N1 and H3N2 strains of influenza, but these differences were not statistically significant.

Researchers are not certain whether the Staphylococcusaureus bacteria caused the lower protection rate or is merely a marker of a poorer immune response. Previous research, however, has shown that Staphylococcus aureus infections can cause immune cells to retreat from the skin and that toxins secreted by Staphylococcus can inhibit the action of antibody-secreting B cells.

“Staphylococcus infections are a widespread problem among atopic dermatitis patients, with up to 90 percent of patients with severe disease colonized by the bacteria,” says lead researcher Donald Leung, MD, PhD, head of pediatric allergy and clinical immunology at National Jewish Health, in a news release. “We believe that atopic dermatitis patients are likely to get the most protection from traditional intramuscular influenza vaccines, rather than intradermal vaccines. We are actively working to better understand immune dysregulation in atopic dermatitis patients.”