"If you're taking aspirin regularly, which many people do for cardiovascular treatment, or acetaminophen (Tylenol) for pain and fever and get a flu shot, there is a good chance that you won't have a good antibody response," Charles Brown of the University of Missouri said in a statement.
"These drugs block the enzyme COX-1, which works in tissues throughout the body. We have found that if you block COX-1, you might be decreasing the amount of antibodies your body is producing, and you need high amounts of antibodies to be protected."
COX enzymes play important roles in the regulation of the immune system, but the role of these enzymes is not yet understood completely, and medications that inhibit them may have adverse side effects, the researchers said.
Arthritis, cardiovascular disease and diabetes are all chronic inflammatory diseases, but inflammation also helps protect individuals from infection, Brown said.
Brown and colleagues tested the drugs on an animal model and have found that these non-steroidal drugs do inhibit vaccines, but the next step is to test it on humans.
The findings were published in The Journal of Immunology.