NEW YORK—Kidney transplant patients have a weaker response to influenza immunization than healthy individuals, especially in the first six months after receiving a transplant, according to a study published in the July issue of the American Journal of Kidney Diseases.
Respiratory viral infections are common among transplant patients, and are cause for concern because they can be particularly harmful to people with suppressed immune systems, Kelly A. Birdwell, MD, MSCI, of VanderbiltUniversityMedicalCenter in Nashville, Tenn., said in her report.
The Centers for Disease Control and Prevention recommends influenza vaccine for kidney transplant patients, but little is known about what kind of antibody response they are able to mount to a flu shot, according to the study. What’s more, no studies have looked exclusively at patients on tacrolimus, now the most commonly used immunosuppressant in kidney transplant patients.
The researchers looked at the response to influenza vaccine in 53 kidney transplant recipients and 106 healthy controls during the 2006-2007 flu season. All of the patients were receiving tacrolimus for immunosuppression.
Birdwell and her team checked vaccine response by testing study participants’ levels of antibodies to three different influenza strains—A/H1N1, A/H3N2, and B—before they received the vaccine and again one month later. The researchers used two criteria to gauge the effectiveness of the vaccine: seroresponse, defined as a four-fold increase in levels of antibodies against a viral strain; and seroprotection, meaning levels of antibodies adequate for protection against infection.
A smaller percentage of the transplant patients achieved seroresponse or seroprotection than the healthy controls. But the differences were statistically significant only for one strain, A/H3N2; among controls, 62.3 percent achieved seroresponse, compared to 34 percent of the transplant patients, while 91.5 percent of controls and 69.8 percent of transplant patients were seroprotected.
